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Quick Review Series (QRS) for BDS 4th Year: Orthodontics is an extremely exam-oriented book. The book includes a collection of last 20 years’ solved question papers of Orthodontics from various ...

Quick Review Series (QRS) for BDS 4th Year: Orthodontics is an extremely exam-oriented book. The book includes a collection of last 20 years’ solved question papers of Orthodontics from various universities like RGUHS, NTRUHS, MUHS, MGRUHS, etc. according to the new syllabus of BDS 4th year.
The book would serve the requirements of final year BDS students to prepare for their examinations as well as help PG aspirants and PGs for quick review of important topics.

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Sample chapter quick review series for bds 4th year orthodontics 1e by rao to order call sms at 91 8527622422 Sample chapter quick review series for bds 4th year orthodontics 1e by rao to order call sms at 91 8527622422 Document Transcript

  • SECTION I TOPIC WISE SOLVED QUESTIONS OF PREVIOUS YEARS Topic 1 Introduction to Orthodontics .................................................................................................... 3 Topic 2 General Principles and Concepts of Growth ............................................................................ 6 Topic 3 Growth and Development of Cranial and Facial Structures ................................................... 20 Topic 4 Development of Dentition and Occlusion ............................................................................... 29 Topic 5 Functional Development ......................................................................................................... 40 Topic 6 Occlusion: Basic Concepts .................................................................................................... 44 Topic 7 Classification of Malocclusion ................................................................................................ 47 Topic 8 Aetiology of Malocclusion....................................................................................................... 60 Topic 9 Oral Habits .............................................................................................................................. 71 Topic 10 Orthodontic Diagnosis ............................................................................................................ 82 Topic 11 Cephalometrics..................................................................................................................... 100 Topic 12 Skeletal Maturity Indicators .................................................................................................. 119 Topic 13 Model Analysis...................................................................................................................... 124 Topic 14 Biology and Mechanics of Tooth Movement ........................................................................ 133 Topic 15 Anchorage ............................................................................................................................ 142 Topic 16 Age Factors in Orthodontics ................................................................................................. 149 Topic 17 Preventive Orthodontics ....................................................................................................... 150 Topic 18 Interceptive Orthodontics ..................................................................................................... 159 Topic 19 Methods of Space Gaining ................................................................................................... 166 Topic 20 Arch Expansion ..................................................................................................................... 171 Topic 21 Extractions ............................................................................................................................ 177 Topic 22 Orthodontic Appliances: General Principles ......................................................................... 181 Orthodontics-Part-I-2013.indd 1 12/3/2013 2:49:10 PM
  • Topic 23 Removable Orthodontic Appliances ..................................................................................... 183 Topic 24 Fixed Orthodontic Appliances .............................................................................................. 199 Topic 25 Myofunctional and Orthopaedic Appliances ........................................................................ 210 Topic 26 Management of Common Malocclusions ............................................................................. 229 Topic 27 Management of Class II Malocclusion.................................................................................. 236 Topic 28 Management of Class III Malocclusion ................................................................................. 241 Topic 29 Management of Open Bite, Crossbite and Deep Bite .......................................................... 245 Topic 30 Cleft Lip and Palate .............................................................................................................. 256 Topic 31 Surgical Orthodontics ........................................................................................................... 263 Topic 32 Retention and Relapse ......................................................................................................... 267 Topic 33 Genetics in Orthodontics ...................................................................................................... 275 Topic 34 Lab Procedures .................................................................................................................... 277 Topic 35 Materials Used in Orthodontics ............................................................................................ 281 Orthodontics-Part-I-2013.indd 2 12/3/2013 2:49:10 PM
  • SECTION I Topic wise Solved Questions of Previous Years 1 Topic INTRODUCTION TO ORTHODONTICS LONG ESSAYS Q. 1. Define orthodontics. Describe aims and science of orthodontics. Or Describe briefly the aims, objectives, scope and limitations of orthodontic treatment. Ans. Orthodontics is the study of growth and development of the masticatory apparatus and the prevention and treatment of abnormalities of this development. According to British Society for the Study of Orthodontics (BSSO), ‘Orthodontics includes the study of growth and development of the jaws and face particularly, and the body generally, as influencing the position of the teeth; the study of action and reaction of internal and external influences on the development, and the prevention and correction of arrested and perverted development’. The aims of orthodontic treatment are as follows: All the branches of dentistry have one common aim, the establishment of as good an occlusion as possible, not only in the functional but also in the aesthetic sense. The aim of orthodontics is to achieve a functional and aesthetically harmonious occlusion by permanently altering the positions of the natural teeth. This is accomplished by careful stimulation of alveolar bone tissue to alter its shape and support the teeth in a more favourable position. The goal of modern orthodontics is to create the best possible occlusal relationship within the framework of acceptable facial aesthetics and stability of the occlusion. Orthodontics-Part-I-2013.indd 3 It may be said that orthodontics seek: ❍ To intercept departures from normal development of the masticatory organs. ❍ To restore conditions to normal development at the earliest when required. ❍ To establish as good an occlusion as possible both in functional and aesthetic senses. It is important that to achieve the results, we do not interfere with normal function for more than what is required. The use of appliances should be kept to minimum possible to attain the desired result, lest they interfere with normal growth changes and produce further abnormality. It has been found (Gardiner, 1956) that at least 50% of all school children may benefit from orthodontic treatment, and dental surgeons in general family practice are often requested by parents to provide such treatment. The objectives of orthodontic treatment are summarized by Jackson into: i. Functional efficiency ii. Structural balance iii. Aesthetic harmony. Aesthetic harmony Functional efficiency Structural balance Fig. 1.1 Jackson’s triad. 12/3/2013 2:49:10 PM View slide
  • Quick Review Series for BDS 4th Year: Orthodontics 4 All the above three objectives put together are popularly known as Jackson’s triad (Fig. 1.1). i. Establishing functional efficiency: Correction of malocclusion eliminates all the unfavourable sequelae of malocclusion and thereby restores the functional efficiency of the masticatory apparatus. ii. Restoring structural balance Achieving structural balance between the hard and soft tissues maintains stability of the corrected malocclusion. Failure to achieve structural balance will lead to relapse or loss of correction achieved. iii. Aesthetic harmony: The prime objective of orthodontic treatment is the improvement of the facial aesthetics and is the single most common reason for the patients to approach an orthodontist. Q. 2. What is orthodontia? Describe various sequelae of malocclusion of teeth. Ans. Orthodontics is the study of growth and development of the masticatory apparatus and the prevention and treatment of abnormalities of this development. The various problems or sequelae of malocclusion are as follows: i. Psychological and social problems ii. Poor appearance iii. Interference with normal growth and development like crossbites causing asymmetry and influences of overbite and overjet. iv. Improper or abnormal muscle functions like hyperactive mentalis, hypoactive upper lip, increased buccinator pressures, tongue thrust and associated muscle habits like lip biting, nail biting, finger sucking, etc. v. Abnormal deglutition vi. Mouth breathing vii. Improper mastication viii. Speech defects ix. Increased caries activity x. Predisposition to periodontal disease xi. Temporomandibular joint (TMJ) problems xii. Impacted and unerupted teeth leading to pathologies like cysts and damage to other teeth xiii. Risk of trauma or accidents xiv. Prosthetic rehabilitation complications. i. Psychological and social problems Irregular and protruding teeth have a negative impact on a patient’s psychology. Children with malocclusion become introvert and their social behaviour is immature. Example: Introversion or self-consciousness and response to nicknames like ‘bugs bunny’, ‘buck teeth’, etc. Orthodontics-Part-I-2013.indd 4 ii. Poor appearance Poor appearance due to malocclusion forms a hindrance to the child’s performance in school as well as in other extracurricular activities like play. Preventive or interceptive measures should be attempted to correct the malocclusion, if it is detected in early stages of child development. iii. Interference with growth and development Perverted perioral muscle activity due to abnormal finger sucking habit could cause morphological and functional changes to the dentition. Common effect of abnormal perioral muscle activity is development of posterior crossbites. Many a time functional aberrations may lead to unilateral crossbite, which in turn, may cause facial asymmetry. Flattening of mandibular anteriors may be caused due to increased deep bite and abnormal lip posture. Anterior occlusal interferences may cause pseudo class III. iv. Abnormal muscle function Abnormal muscle activity could be contributing to malocclusion. In case of lip trap, cushioning of lower lip behind the proclined upper incisors may aggravate the proclination. v. Improper deglutition: Many malocclusions result in abnormal functioning of stomatognathic system like improper deglutition. vi. Mouth breathing: Malocclusions like increased overjet can result in mouth breathing usually correction of increased overjet can make lip closure possible, establishing anterior oral seal and making nasal breathing possible. vii. Improper mastication: Malaligned teeth change the pattern of chewing, which can lead to TMJ problems, periodontal problems, etc. viii. Speech defects Malocclusion affects the speech pattern of individuals. Effect of cleft lip: Speech problem in cleft patients is due to velopharyngeal incompetence, naso-oral communication, abnormal tongue posture and function, and lip tissue inadequacy. ix. Increased predilection to caries and periodontal diseases Irregular teeth make self-cleansing of oral cavity less effective and may lead to increased susceptibility to caries and periodontal diseases. Loss of proper contact between teeth and abnormal axial inclinations could lead to uneven distribution of functional stresses, which in turn can lead to periodontal problems. x. TMJ disorders: Malocclusion causes TMJ problems like clicking, crepitus, pain and dysfunction. 12/3/2013 2:49:10 PM View slide
  • Topic wise Solved Questions of Previous Years 5 xi. Malocclusion and trauma: One of the most common problems associated with class II division 1 malocclusion is high risk of trauma to maxillary anterior teeth. xii. Impacted and unerupted tooth Impacted teeth may interfere with eruption of the successor or neighbouring tooth, and may also cause resorption of the roots of the adjacent tooth. Possibility of development of pathologies like cysts due to impacted or unerupted tooth is most likely. xiii. Prosthetic rehabilitation problems: Supraeruption of the tooth into opposing edentulous area and tipping of teeth into adjacent edentulous area causes space problems for prosthetic rehabilitation. SHORT ESSAYS Q. 1. Objectives of orthodontics Ans. The objectives of orthodontic treatment are summarized by Jackson into: i. Functional efficiency ii. Structural balance iii. Aesthetic harmony. All the above three objectives put together are popularly known as Jackson’s triad. i. Establishing functional efficiency: Correction of malocclusion eliminates all unfavourable sequelae of maloc- clusion and thereby restores the functional efficiency of the masticatory apparatus. ii. Restoring structural balance Achieving structural balance between the hard and soft tissues maintains stability of the corrected malocclusion. Failure to achieve structural balance will lead to relapse or loss of correction achieved. iii. Aesthetic harmony: The prime objective of orthodontic treatment is improvement of the facial aesthetics and is the single most common reason for the patients to approach an orthodontist. SHORT NOTES Q. 1. Aims of orthodontics Or Aims and scope of orthodontics Ans. The aims of orthodontics are as follows: i. To intercept departures from normal development of the masticatory apparatus ii. To restore conditions for normal development at the earliest when required iii. To establish as good an occlusion as possible—both in functional and aesthetic senses. The goal of modern orthodontics is to create the best possible occlusal relationship within the framework of acceptable facial aesthetics and stability of the occlusion. Q. 2. Jackson’s triad Or Describe Andrews Jackson’s triad. Orthodontics-Part-I-2013.indd 5 Ans. The objectives of orthodontic treatment are briefly summarized by Jackson into: i. Functional efficiency ii. Structural balance iii. Aesthetic harmony. All the above three objectives put together are popularly known as Jackson’s triad. i. Establishing functional efficiency: Correction of malocclusion eliminates all unfavourable sequelae of malocclusion and thereby restores the functional efficiency of the masticatory apparatus. ii. Restoring structural balance: Achieving structural balance between the hard and soft tissues maintains stability of the corrected malocclusion. iii. Aesthetic harmony: The prime objective of orthodontic treatment is improvement of the facial aesthetics and is the most common reason for the patients to approach an orthodontist. Q. 3. Define interceptive and preventive orthodontics. 12/3/2013 2:49:10 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 6 Ans. According to Graber, interceptive orthodontics is ‘the phase of the science and art of orthodontics employed to recognize and eliminate potential irregularities in the developing dentofacial complex’. Graber defined preventive orthodontics as ‘the action taken to preserve the integrity of what appears to be the normal occlusion at a specific time’. Q. 4. Define orthodontics. Or Give the BSSO definition of orthodontics. Ans. Orthodontic treatment for adults is broadly classified into two types: i. Adjunctive orthodontic treatment ii. Comprehensive orthodontic treatment. Adjunctive orthodontic treatment procedures are carried out to facilitate other dental procedures to control disease and restore function. For example, uprighting of molars, forced eruption, crossbite correction, diastema closure, etc. Comprehensive orthodontic treatment is an essential treatment procedure carried out in children for correction of malocclusion. Response to orthodontic force is slightly slower in adults as compared to children. Q. 6. Contributions of EH Angle to orthodontics Orthodontics is the study of growth and development of the masticatory apparatus and the prevention and treatment of abnormalities of this development. According to British Society for the Study of Orthodontics (BSSO), ‘orthodontics includes the study of growth and development of the jaws and face particularly, and the body generally, as influencing the position of the teeth; the study of action and reaction of internal and external influences on the development, and the prevention and correction of arrested and perverted development’. Q. 5. Adult orthodontics Ans. Ans. Edward H Angle is considered as the ‘father of modern orthodontics’ for his numerous contributions to the speciality of orthodontics, which are as follows: i. Publication of book on orthodontics in 1887 ii. Concept of ‘occlusion in orthodontics’ iii. Hypothesis of ‘key of occlusion’ iv. Classification of malocclusion v. Various appliances like a. Angle’s E-arch, b. Pin and tube, c. Ribbon arch appliance and d. Edgewise appliance. Orthodontic treatment of adults is known as adult orthodontics. Topic 2 GENERAL PRINCIPLES AND CONCEPTS OF GROWTH LONG ESSAYS Q. 1. Define growth and development. Mention various theories of growth and write in detail about functional matrix hypothesis. Or Enumerate various theories of growth. Explain in detail the functional matrix theory. Or Enumerate various theories of growth. Describe functional matrix theory of Moss. Orthodontics-Part-I-2013.indd 6 Or Enumerate theories of bone growth. Ans. Based on the expression of intrinsic genetic potential various theories of craniofacial growth are: i. Genetic theory by Brodie ii. Sutural dominance theory by Sicher iii. Cartilaginous theory by Scott iv. Functional matrix theory by Melvin Moss v. Van Limborgh’s theory. 12/3/2013 2:49:10 PM
  • Topic wise Solved Questions of Previous Years 7 Other concepts/theories related to craniofacial growth are: i. Hunter and Enlow’s growth equivalent concept ii. Petrovic’s cybernetic theory. Functional matrix theory (Melvin Moss) The functional matrix concept attempts to comprehend the relation between form and function. Functional matrix hypothesis was put forward by Melvin Moss based on the work of Van der Klaauw. The theory is simply stated as ‘there is no direct genetic influence on the size, shape or position of skeletal tissues, only the initiation of ossification. All skeletogenic activities are primarily based upon the functional matrices.’ According to original version of functional matrix hypothesis: Head is a composite structure—operationally consisting of number of relatively independent functions. For example, digestion, respiration, vision, olfaction, speech equilibrium and neural integration, etc. Each function is carried out by a group of soft tissues, which are supported and protected by related skeletal elements. Soft tissues and skeletal elements related to single function are known as functional cranial component. Associated with one single function, totally all the i. skeletal elements are known as skeletal unit. ii. soft tissues are known as functional matrix. It was demonstrated that the origin, growth and maintenance of the skeletal unit depends almost exclusively upon its functional matrix. 1968 Updated version of Melvin Moss’s hypothesis Functional matrix hypothesis claims that the origin, form, position, growth and maintenance of all skeletal tissues and organs is always secondary, compensatory and necessary response to chronologically and morphologically prior events or processes that occur in specifically related non-skeletal tissues, organs or functional spaces. Each of independent function in craniofacial region is carried out by: functional cranial component (consists of all tissues + organs + spaces and skeletal parts necessary to carry out given function). Functional cranial component is divided into: i. Functional unit: Comprises all the tissues, organs and functioning spaces as a whole. ii. Skeletal unit: Skeletal tissues related to specific function matrix. Skeletal unit It is comprised of bone, cartilage and tendinous tissue. It is nothing but all skeletal tissues associated with a single function. Orthodontics-Part-I-2013.indd 7 It is divided into: i. Microskeletal unit ii. Macroskeletal unit. Microskeletal unit Macroskeletal unit When a bone is comprised of several contiguous skeletal units, it is known as microskeletal units. Example: i. Mandible has following microskeletal units: alveolar, angular, condylar, gonial, mental, coronoid and basal. ii. Maxilla has following microskeletal units: orbital, pneumatic, palatal and basal. When adjoining portions of a number of neighbouring bones are united to function as a single cranial component, it is termed as macroskeletal unit. Example: i. Entire endocranial surface of the calvarium. Functional matrix It consists of muscles, glands, nerves, vessels, fat, teeth and functioning spaces. Functional matrix is divided into: i. Periosteal matrix ii. Capsular matrix. Periosteal matrix Capsular matrix It includes muscles, blood ves- It includes neurocranial capsule sels, nerves and glands. and orofacial capsule. They act directly and actively upon their related skeletal units bringing about transformation in their size and shape by bone deposition and resorption. They act indirectly and passively on their related skeletal units producing a secondary compensatory translation in space. Capsular matrix Neurocranial capsule Orofacial capsule It is made up of skin, connective tissue, aponeurotic layer, loose connective layer, periosteum, base of the skull and two layers of dura mater, which surround and protect neurocranial capsular functional matrix, which is brain, leptomeninges and cerebrospinal fluid. Surrounds and protects the oronasopharyngeal spaces, which constitute the orofacial capsular matrix. The growth of facial skull is influenced by volume and patency of these spaces. Each of the neurocranial and orofacial capsule is an envelope that contains series of functional cranial components (i. e. skeletal units and functional matrix), which as a whole is sandwiched between two covering layers. The alterations in special position of skeletal units is brought about by the expansion of these capsules within 12/3/2013 2:49:10 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 8 which the respective bones arise, grow and are maintained. The skeletal units are passively and secondarily moved in space, as their enveloping capsule is expanded. This kind of translative growth is not brought about by deposition and resorption. Clinical implications of functional matrix theory Orthodontic corrections of teeth are done either by intraoral or extraoral appliances. The forced application by these appliances tends to alter the functional matrix. Alteration of periosteal functional matrix produces changes in microskeletal unit, i.e. alveolar bone while the alteration of capsular functional matrix produces changes in macroskeletal unit, i.e. jaws. Q. 2. Define growth and enumerate various theories of bone growth. Ans. Growth has been defined by various clinicians in different ways as follows: JS Huxley defined growth as ‘the self-multiplication of living substance.’ Krogman defined growth as ‘increase in size, change in proportion and progressive complexity.’ Todd defined growth as ‘an increase in size.’ Meredith defined growth as ‘entire series of sequential anatomic and physiologic changes taking place from the beginning of prenatal life to senility.’ Moyers defined growth as ‘quantitative aspect of biological development per unit of time.’ Moss defined growth as ‘change in any morphological parameter that is measurable.’ Based on the expression of intrinsic genetic potential various theories of craniofacial growth are: i. Genetic theory by Brodie ii. Sutural dominance theory by Sicher iii. Cartilaginous theory by Scott iv. Functional matrix theory by Melvin Moss v. Van Limborgh’s theory. Other concepts/theories related to craniofacial growth are: i. Hunter and Enlow’s growth equivalent concept ii. Petrovic’s cybernetic theory. i. Genetic theory This is one of the earliest theories put forward by Brodie in 1941. Brodie stated simply that all growth is controlled by the genes and is preplanned. This theory is more of an assumption and is not proved. Primary genetic control determines only certain features and does not have complete influence on overall growth. Orthodontics-Part-I-2013.indd 8 ii. Sicher’s sutural dominance theory/Sicher’s hypothesis/ Sutural theory Sutural dominance theory was put forward by Sicher. According to him bone growth within the various craniofacial units is the result of growth taking place in sutures. According to Sicher, the growth of the skull tissue is controlled by its own genetic potential. According to him, all bone-forming elements like cartilage, sutures and periosteum are growth centres. This theory is also known as sutural dominance theory because proliferation of connective tissue and its replacement by bone in the suture is considered to be the primary event. Growth taking place in the sutures that connect maxillary complex to the cranium causes downward movement of the midface. Drawbacks of sutural theory Any unusual pressure on suture initiates bone resorption and not bone’s deposition as it is a tension-adapted tissue. Sutures do not act as primary growth centres. Growth in the sutural area is a secondary response to functional needs. Evidence in favour of secondary role of sutural growth is more. Based on various experimental studies it was shown that extirpation or removal of facial sutures had no effect on the growth of skeleton. iii. Cartilaginous theory Cartilaginous theory is also known as Scott’s hypothesis or nasal septal theory, and is put forward by James Scott. This theory is based on the principle that intrinsic growth controlling factors are present in cartilage and periosteum. According to Scott, cartilaginous sites throughout the skull are primary growth centres and growth of cartilage in nasal septum provides force that displaces maxilla downwards and forwards. Nasal septum is considered to be the major contributor in maxillary growth. In mandible, condylar cartilage is considered to be the growth centre present bilaterally with the horseshoeshaped mandible in between. Experimental evidence in favour of this theory are: Removal of nasal septal cartilage in rats and rabbits resulted in deficient snout of these animals. Transplantation of part of epiphyseal plate and synchondroses to a different location results in continued growth in the new location, which indicates innate growth potential of the cartilage. Nasal septum also shows innate growth potential on being transplanted to a different location. iv. Functional matrix theory (Melvin Moss) The functional matrix concept attempts to comprehend the relation between form and function. 12/3/2013 2:49:10 PM
  • Topic wise Solved Questions of Previous Years 9 Functional matrix hypothesis was put forward by Melvin Moss based on the work of van der Klaauw. The theory is simply stated as ‘there is no direct genetic influence on the size, shape or position of skeletal tissues, only the initiation of ossification. All skeletogenic activity is primarily based upon the functional matrices.’ Head is a composite structure. Each function is carried out by a group of soft tissues supported and protected by related skeletal elements. Soft tissues and skeletal elements related to single function are known as functional cranial component. Associated with one single function, totally all the i. skeletal elements are known as skeletal unit. ii. soft tissues are known as functional matrix. It was demonstrated that the origin, growth and maintenance of the skeletal unit depends almost exclusively upon its functional matrix. 1968 Updated version of Melvin Moss hypothesis Functional matrix hypothesis claims that the origin, form, position, growth and maintenance of all skeletal tissues and organs are always secondary, compensatory and necessary responses to chronologically and morphologically prior events or processes that occur in specifically related non-skeletal tissues, organs or functional spaces. Each of the independent functions in craniofacial region are carried out by functional cranial component, which consists of all tissues, organs, spaces and skeletal parts necessary to carry out given function. v. van Limborgh’s theory van Limborgh in 1970 put forward a multifactorial theory. He explained the process of growth and development in a view that combines all three existing theories: (i) functional matrix theory, (ii) sutural theory by Sicher and (iii) genetic theory. According to van Limborgh the five factors that control the growth are as follows: i. Intrinsic genetic factors: They are genetic control of the skeletal units themselves. ii. Local epigenetic factors: Bone growth is determined by genetic control originating from adjacent structures like brain, eyes, etc. iii. General epigenetic factors: They are genetic factors determining growth from distant structures, e.g. sex hormones, growth hormones. iv. Local environmental factors: Non-genetic factors from local external environment, e.g. habits, muscle force. v. General environmental factors: Non-genetic general environment, e.g. nutrition, O2. Views expressed by van Limborgh can be summarized as follows: Chondrocranial and desmocranial growth are controlled by ‘intrinsic genetic factors.’ Orthodontics-Part-I-2013.indd 9 Cartilaginous parts of skull are considered as growth centres. Sutural and periosteal growths are additionally governed by local non-genetic environmental infamies. Sutural growth is controlled by influences originating from skull cartilages and other adjacent skull structures. Periosteal growth to a large extent depends on growth of adjacent structures. Other concepts/theories related to craniofacial growth are: Hunter and Enlow’s growth equivalent concept According to Enlow’s expanding ‘V’ principle: Many facial bones or parts of bone have a ‘V’-shaped pattern of growth. In these bones, the growth movements and enlargement occurs towards the wide ends of the ‘V’ as a result of differential deposition and selective resorption of bone. Bone deposition occurs on the inner side of the wide end of the ‘V’ and bone resorption on the outer surface. Deposition also takes place at the ends of the two arms of the ‘V’ resulting in growth movement towards the ends. The ‘V’ pattern of the growth occurs in a number of regions such as the base of the mandible, ends of long bones, mandibular body, palate, etc. Q. 3. Enumerate the various methods of measuring growth. Discuss the clinical importance of the knowledge of growth and development in orthodontics. Or What are the methods of measuring growth and discuss the importance of the knowledge of growth and development in orthodontics? Ans. Various methods of measuring growth are as follows: i. Proffit’s classification ii. Moyer’s classification Proffit’s classification i. ii. iii. iv. v. vi. Measurement approaches Anthropometry Craniometry Cephalometry Arcial growth Logarithmic spiral Finite element analysis i. ii. iii. iv. Experimental approaches Vital staining Radioactive tracer Autoradiography Implant radiography Moyer’s classification It is of following types: i. Quantitative ii. Observations 12/3/2013 2:49:11 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 10 iii. Rating and ranking iv. Opinions. The quantitative method of measuring growth is again of following types: Direct measurements Indirect measurements Combination i. Anthropometry i. Study casts i. Radiography and implants ii. Craniometry ii. Radiographs ii. Radiograph + metaphysic bands iii. Vital staining iii. Photographs iii. Autoradiography iv. Implant markers v. Histochemistry The various methods of measuring growth in detail are as follows: I. Craniometry and anthropometry Craniometry is the art of measuring skulls so as to discover their specific differences. Precise measurements can be made with craniometry. It is a cross-sectional type of study. Site, amount and rate of growth cannot be elicited by craniometry but gives information about direction of growth to some extent. Anthropometry is the measurement of skeletal dimensions on living individuals. It is a longitudinal study. Anthropometry gives little information about amount of growth and to some extent rate of growth, whereas it gives relatively accurate information about direction of growth. Clinical uses Cranial index and facial index are two important indices used in orthodontics. Index is the ratio of smaller to a larger linear measurement expressed by means of percentage. Cranial index = Maximum cranial breadth × 100 Maximum cranial length Maximum cranial breadth is the measured distance between the two most prominent points on either side of the head. Maximum cranial length is the measured distance from glabella to opisthocranion—the most prominent point of the occipital bone in the midline. The values of cranial index are more for brachycephalic/ short and round head types around 80–85 and less for dolichocephalic/long narrow head type around 70–75, while for mesocephalic/middle type the values are in between the above two. Facial index = Orthodontics-Part-I-2013.indd 10 Facial height × 100 Zygomatic breadth Facial height is the measured distance from nasion to gnathion whereas zygomatic breadth is the distance between two zygomas. The values of facial index are more for leptoprosopic, i.e. high and narrow facial type 90–95 and less for euryprosopic, i.e. broad and round facial type 80–85 and average in between these two values for mesoprosopic, i.e. middle type around 85–90. II. Vital staining Vital staining is an experimental method of measuring growth introduced by John Hunter in 18th century. Commonly used dyes for vital staining are: Alizarin S Radioactive tracers Fluorochrome Tetracycline Trypan blue Procedure This technique involves injecting certain dyes that stain the mineralizing tissues and get incorporated in the bones and teeth. Animals are sacrificed and tissues are studied histologically for manner in which bone is laid down, the site of growth, the direction, duration and amount of growth at different sites in the bone. Disadvantage of this method is that it is not a longitudinal study; hence, repeated data of the same individual cannot be obtained. III. Implant radiography Use of implant radiograph to study bone growth was introduced by Professor Bjork in 1969. It is an experimental method for studying physical bone growth. Procedure It involves inserting small bits of biologically inert metal alloys into growing bone of either mandible or maxilla. Very tiny metallic implants of size 1.5 mm long and 0.5 mm diameter made of tantalum are used. Osseointegrated implants serve as reference points; and serial cephalometric radiographs are taken repeatedly over a period of time and compared. Preferable site of implants in mandible and maxilla are as follows: i. Mandible Anterior aspect of symphysis in the midline below roots. Two pins on the right side body of mandible: one below first premolar and another below second premolar or first molar. External surface of ramus on the right side at the level of occlusal surface of molars. 12/3/2013 2:49:11 PM
  • Topic wise Solved Questions of Previous Years 11 ii. Maxilla Hard palate behind deciduous canines After eruption of maxillary incisors below the anterior nasal spine Bilaterally one implant on either side of zygomatic process of maxilla The patterns are the controlling or restricting mechanisms to preserve the integration of parts of the body under varying conditions. Differential growth (cephalocaudal growth, Scammon’s growth) and predictability are the contributors to pattern. Junction of hard palate and alveolar process medial to first molar: Implant radiography gives very accurate information about the site, amount and direction of growth while a relatively accurate information about rate of growth. Drawbacks of this method are that it is a two-dimensional study of three-dimensional process and radiation hazard. Throughout life human body does not grow at the same rate; different organs grow at different rates to a different amount and at different times. This is known as differential growth. The concepts of differential growth are more clearly understood by two important aspects of growth: a. Cephalocaudal gradient of growth b. Scammon’s curve of growth. Q. 4. Define growth. Discuss briefly clinical application of knowledge of growth and development in orthodontics. Ans. Growth has been described in so many terms. Todd defined growth as ‘increase in size.’ Krogman defined it as ‘increase in size and change in spatial proportion over time.’ Huxley defined it as ‘self-multiplication of the living tissues.’ Moss defined growth as ‘any change in morphology that is within measurable parameter.’ Meredith defined growth as ‘the entire series of anatomic and physiologic changes taking place between the beginning of prenatal life and the close of senility.’ Moyer defined growth as ‘the biologic process by which living matter gets larger.’ Development is defined in simple words as ‘progression towards maturity.’ According to Melvin Moss, ‘development can be considered as a continuum of causally related events from the fertilization of ovum onwards.’ Importance of knowledge of growth and development in orthodontics is as follows: Craniofacial growth is a complex phenomenon. A thorough knowledge of the normal pattern of growth and normal variations will help in identifying the problems and also utilize the normal growth to advantage in treatment. Clinical implications of growth and development can be studied under the following headings: i. Growth pattern ii. Differential growth iii. Variability iv. Timing variations v. Safety valve mechanism. i. Growth pattern Definite arrangement of designs in definite proportional relationship is known as pattern. In relation to growth, pattern can be defined as proportional relationship over time. Orthodontics-Part-I-2013.indd 11 ii. Differential growth a. Cephalocaudal gradient of growth An axis of increased growth gradient extending from head towards the feet is called ‘cephalocaudal growth.’ In fetal life, head constitutes 50% of total body length while limbs are primitive (30%). At the time of birth head constitutes 25–30% and there is an increased growth of body and limbs. In an adult the head constitutes only 12%, while limbs account to 50%. These changes in the pattern of growth are because of cephalocaudal gradient. Cephalocaudal growth of face: At the time of birth jaws and face are less developed compared to skull. Maxilla being closer to head grows faster and growth is completed before mandibular growth. Mandible being away from the brain grows more and growth completes later than maxilla. b. Scammon’s curve of growth Major tissues of the human body are divided into four types: i. Lymphoid tissue ii. Neural tissue iii. General tissue iv. Genital tissue. These different tissues grow at different time and at different rates. i. Lymphoid tissue: It proliferates rapidly in late childhood to almost 200% of adult size. Adaptation to protect child from infection—by 18 years it undergoes involution to reach adult size. ii. Neural tissue: Grows very rapidly and almost reaches adult size by 6–7 years of age after that a very little growth occurs in neural tissue. iii. General/visceral and muscle, bone and other organs: They exhibit ‘S’-shaped curve of rapid growth up to 2–3 years of age: a. followed by slow phase between 3 and 10 years of age. b. followed by rapid phase of growth occurring after 10th year, and terminating between 18 and 20 years. 12/3/2013 2:49:11 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 12 iv. Genital tissue (reproductive organs) Negligible growth until puberty. They grow rapidly at puberty reaching adult size, after which growth ceases. Effect of Scammon’s growth in facial region: ❍ Mandible follows somatic growth pattern. Longtime growth is seen until about 18–20 years in males. ❍ Maxilla follows neural growth pattern and growth ceases earlier; hence skeletal problems of the maxilla should be treated earlier to mandible. iii. Variability of growth Variability of growth is the law of nature. No two individuals mimic alike, and no two individuals grow in the same pattern. The reasons for variability of growth are as follows: a. Variation within normal range: Evaluated by Wetzel’s grid. b. Variation due to other influences includes the following: i. Heredity ii. Nutrition iii. Racial difference iv. Climate v. Exercise vi. Socioeconomic factors vii. Psychological factors viii. Size of the family ix. Hormonal changes. c. Variation due to timing effects is due to the following: i. Body build ii. Sex difference iii. Growth spurts. Variation within normal range It is evaluated by Wetzel’s grid. The resultant curve obtained by plotting the height and weight of an individual against the age over a period of time is compared with normal range. Any unexpected growth pattern changes should be evaluated and investigated for growth abnormality. b. Variation due to other influences Heredity: On rate of growth and onset of menarche, there is genetic control. Nutrition: Certain parts of the body may be affected by malnutrition and show retardation of growth. Racial differences: Differences in skeletal maturity are exhibited by different races. Orthodontics-Part-I-2013.indd 12 Climate and seasonal effects: People living in cold places have more of fat or adipose tissue. Exercise: Increases muscle mass and physique. c. Variation due to timing effects Timing variations in growth is nothing but occurrence of same events at different times for different individuals. iv. Timing variation in growth i. Body build ii. Sex difference iii. Growth spurts Body build Ectomorphic: Late-maturing individuals grow for a longer period. Mesomorphic: Individuals exhibiting average growth period. Endomorphic: Early-maturing individuals, where growth completes much faster. Sex differences Boys and girls exhibit variation between onset of menarche and rate of growth. In girls, there is early onset of menarche and growth completes faster than boys of the same age. In the boys, there is delayed onset of puberty and growth occurs over a longer period. Growth spurts Growth does not take place uniformly at all times. There seem to be periods when a sudden acceleration of growth occurs. This sudden increase in growth is termed growth spurt. The growth spurts can be utilized for growth modulation treatment. v. Safety valve mechanism Safety valve mechanism is a nature’s attempt to maintain proper occlusion. To compensate for the horizontal growth in mandible, the maxillary intercanine width serves as a safety valve. In mandible the intercanine width is completed at 9 years of age in girls and at around 10 years of age in boys. In the maxilla the intercanine width is completed by 12 years in girls and at 18 years in boys. The delay in growth of maxillary intercanine arch width serves as a ‘safety valve’ for pubertal growth spurts in mandible. Maxillary intercanine width adjusts to the mandibular dentition as it is brought forward. This is called ‘safety valve mechanism.’ 12/3/2013 2:49:11 PM
  • Topic wise Solved Questions of Previous Years 13 SHORT ESSAYS Q. 1. Growth spurts Or Growth spurts and two clinical importance Or Pubertal growth spurts Ans. Growth does not take place uniformly at all times. There seems to be periods when a sudden acceleration of growth occurs. This sudden increase in growth is termed growth spurt. Aetiology The physiologic alteration in hormonal secretion. The timing of the growth spurts differ in boys and girls. They are as follows: i. Just before birth ii. One year after birth iii. Mixed dentition growth spurt (boys 8–11 years and girls 7–9 years) iv. Prepubertal growth spurt (boys 14–16 years and girls 11–13 years). Clinical importance Knowledge of growth spurts is essential for successful treatment planning in orthodontics. Growth modulation by means of functional and orthodontic appliances elicits better response during growth spurts. Surgical correction involving maxilla and mandible should be carried out only after cessation of the growth spurts. During pubertal growth spurts there is change in growth direction from vertical to horizontal. Periods of maximum growth are suitable for arch expansion and rapid skeletal expansion procedures. Growth spurt period is the best time for interceptive orthodontic procedures. Q. 2. Methods of gathering growth data Or Methods of studying growth Or What are growth studies? Ans. The various growth studies are as follows: i. Longitudinal studies Orthodontics-Part-I-2013.indd 13 ii. Cross-sectional studies iii. Semilongitudinal studies. Longitudinal studies This type of study consists of the observation and measurements pertaining to growth made on a person or a group of persons at regular intervals over a prolonged period of time. The longitudinal studies are long-term studies where the same sample is studied by means of follow-up examination. Advantages The specific developmental pattern of an individual can be studied and compared, as the same subjects are followed up over a long period. Developmental variations among individuals within the sample can be studied. Disadvantages A long period of time is involved; it often takes years or decades to complete a study. These studies require maintenance of laboratory research personnel and data storage systems for a long period of time. They can be expensive. As these studies are performed over prolonged periods of time, there is a risk of the reduction of sample size due to change of place or other unforeseen events. 2. Cross-sectional studies Cross-sectional studies are carried out by observation and measurement made of different samples and studied at different periods. Advantages These studies are of short duration. They are less expensive. It is possible to repeat the study in case of any flaw. 3. Semilongitudinal studies In these studies, it is possible to combine the cross-sectional and longitudinal methods to derive the advantages of gathering growth data. Types of growth data The physical growth can be studied by a number of ways: i. Opinion It is a clever guess of an experienced person and is the crudest means of studying growth. This method of studying growth is not very scientific and should be avoided when better methods are available. 12/3/2013 2:49:11 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 14 ii. Observations A method of gathering growth-related information by observation. They are useful in studying all or none of the phenomena such as presence or absence of disease. Example: Presence or absence of a caries, class II molar relation. iii. Ratings and rankings Rating makes use of standard, conventionally accepted scales for classification. Ranking involves the arrangement of data in an orderly sequence based on the value. Whenever it is difficult to quantify a particular data, it is possible to adopt a method of rating and ranking. resulting in the displacement of maxilla in forward and downward direction. ii. Secondary displacement: If a displacement of bone occurs as a result of growth and enlargement of adjacent bone, it is known as secondary displacement. Example: Growth of the cranial base results in the forward and downward displacement of the maxilla. Q. 4. Functional matrix theory Or Functional matrix theory of growth and development Quantitative measurements Ans. A scientific approach to study growth is based on accurate measurements, which are of three types: i. Direct data: Direct data are obtained from measurements that are taken on living persons or cadavers by means of scales, measuring tapes or callipers. ii. Indirect data: The growth measurements derived from images, photographs, radiographs or dental casts of a person. iii. Derived data: The data that is derived after comparing two measurements. These two sets of measurements can be of different time frames or of two different samples. Functional matrix hypothesis was put forward by Melvin Moss based on the work of van der Klaauw. The theory is simply stated as ‘there is no direct genetic influence on the size, shape or position of skeletal tissues, only the initiation of ossification. All skeletogenic activities are is primarily based upon the functional matrices.’ According to original version of functional matrix hypothesis: Head is a composite structure operationally consisting of number of relatively independent functions. Example: digestion, respiration, vision and neural integration. Each function is carried out by a group of soft tissues, which are supported and protected by related skeletal elements. Soft tissues and skeletal elements related to single function are known as functional cranial component. Functional cranial component is divided into: i. Functional matrix comprises all the tissues, organs and functioning spaces as a whole. ii. Skeletal unit comprises skeletal tissues related to specific functional matrix. It was demonstrated that the origin, growth and maintenance of the skeletal unit depends almost exclusively up on its functional matrix. Q. 3. Discuss drift and displacement with examples. Ans. Drift and displacement are two basic modes of movements involved during growth. Overall process of craniofacial enlargement is a combination of drift and displacement. Cortical drift Growth of most bones occurs due to interplay of bone deposition and resorption. A combination of bone deposition and resorption resulting in a growth movement towards the depositing surface is called cortical drift. If bone deposition and resorption on either side of a bone are equal, the thickness of the bone remains constant. If in case more bone is deposited on one side and less bone resorbed on the opposite side the thickness of the bone increases. Drift occurs in all the regions of growing bones producing generalized enlargement as well as relocation of parts. Displacement The movement of the whole bone as a unit is known as displacement. It can be of two types: (i) primary and (ii) secondary. i. Primary displacement: If a bone gets displaced as a result of its own growth, it is known as primary displacement. Example: Growth of the maxilla at the tuberosity region causes pushing of the maxilla against the cranial base Orthodontics-Part-I-2013.indd 14 Functional matrix It consists of muscles, glands, nerves, vessels, fat, teeth and functioning spaces. It is divided into two types: i. Periosteal matrix ii. Capsular matrix. Periosteal matrix Capsular matrix It includes muscles, blood ves- It includes neurocranial capsule sels, nerves, glands, etc. and orofacial capsule. It acts directly and actively upon its related skeletal units, and brings about transformation in their size and shape by bone deposition and resorption. It acts indirectly and passively on its related skeletal units producing a secondary compensatory translation in space. 12/3/2013 2:49:11 PM
  • Topic wise Solved Questions of Previous Years 15 Capsular matrix has neurocranial capsule and orofacial capsule. Each of the neurocranial capsule and orofacial capsule is an envelope that contains series of functional cranial components (i.e. skeletal units and functional matrix), which as a whole is sandwiched between two covering layers. The alterations in special position of skeletal units is brought about by the expansion of these capsules, within which the respective bones arise, grow and are maintained. The skeletal units are passively and secondarily moved in space as their enveloping capsule is expanded. This kind of translative growth is not brought about by deposition and resorption. Clinical implications of functional matrix theory The force application by orthodontic appliances tends to alter the functional matrix. Alteration of periosteal functional matrix produces changes in microskeletal unit, i.e. alveolar bone while the alteration of capsular functional matrix produces changes in macroskeletal unit, i.e. jaws. Q. 5. Neurotrophism Ans. A non-impulse transmitting neural function that involves axoplasmic transport and provides for long-term interaction between neurons and innervated tissues that homeostatically regulate the morphological, compositional and functional integrity of those tissues is known as neurotrophism. Presently, the nature of neurotrophic substances and the process of their introduction into the target tissue is unknown. The various types of neurotrophic mechanisms are: i. Neuroepithelial trophism ii. Neurovisceral trophism iii. Neuromuscular trophism. Neuroepithelial trophism: There is a neurotrophic control over epithelial mitosis and synthesis. Certain neurotrophic substances released by the nerve synapses control the normal epithelial growth. If this neurotrophic process is lacking or deficient, abnormal epithelial growth, orofacial hypoplasia and malformation, etc. occur. Example: The presence of taste buds is dependent upon an intact innervation. The nerves are not only important for the sensation of taste but also for healthy growth of the taste buds. If the taste buds are deinnervated, they become atrophic. Neuromuscular trophism: Embryonic myogenesis is independent of neural innervation and trophic control. The neural innervation is established approximately at the myoblast stage of differentiation, without which further continuation of myogenesis usually does not occur. Orthodontics-Part-I-2013.indd 15 Neurovisceral trophism: Visceral organs like the salivary glands, fat tissue and other organs are trophically regulated, at least in part. Q. 6. Scammon’s curve Or Explain differential growth and Scammon’s growth curve. Or Cephalocaudal gradient of growth Ans. Human body does not grow at the same rate human body does not grow at the same rate throughout life; different organs grow at different rates to a different amount and at different times. This is known as differential growth. The concepts of differential growth are more clearly understood by two important aspects of growth: i. Cephalocaudal gradient of growth ii. Scammon’s cure of growth. i. Cephalocaudal gradient of growth An axis of increased growth gradient extending from head towards the feet is called ‘cephalocaudal growth.’ In fetal life, head constitutes 50% of total body length while limbs are primitive (30%). At the time of birth, head constitutes 25–30% and there is increased growth of body and limbs. In an adult, the head constitutes only 12%, while limbs accounts to 50%. These changes in the pattern of growth are because of cephalocaudal gradient. Cephalocaudal growth of face: At the time of birth, jaws and face are less developed compared to skull. Maxilla being closer to head grows faster and growth is completed before mandibular growth. Mandible being away from the brain grows more and growth completes later than maxilla. ii. Scammon’s curve of growth Major tissues of the human body are divided into four types: i. Lymphoid tissue ii. Neural tissue iii. General tissue iv. Genital tissue. These tissues grow at different time and at different rates. i. Lymphoid tissue: It proliferates rapidly in late childhood to almost 200% of adult size. Adaptation to protect child from infection—by 18 years it undergoes involution to reach adult size. ii. Neural tissue: Grows very rapidly and almost reaches adult size by 6–7 years of age; after that a very little growth occurs in neural tissue. 12/3/2013 2:49:11 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 16 iii. General or visceral (muscle, bone and other organs): They exhibit ‘S’-shaped curve with rapid growth up to 2–3 years of age: a. followed by slow phase between 3 and 10 years of age. b. followed by rapid phase of growth occuring after 10th year and terminating between 18 and 20 years. iv. Genital tissue (reproductive organs): Negligible growth until puberty. They grow rapidly at puberty, reaching adult size; after which growth ceases. Effect of Scammon’s growth in facial region Mandible follows somatic growth pattern. Long-time growth is seen until about 18–20 years in males. Maxilla follows neural growth pattern and growth ceases earlier; hence skeletal problems of the maxilla should be treated earlier to mandible. Q. 7. Safety valve mechanism Ans. Safety valve mechanism is a nature’s attempt to maintain proper occlusion. To compensate for the horizontal growth in mandible, the maxillary intercanine width serves as a safety valve. In mandible the intercanine width is completed at 9 years of age in girls and at around 10 years of age in boys. In the maxilla the intercanine width is completed by 12 years in girls and at 18 years in boys. The delay in growth of maxillary intercanine arch width serves as a ‘safety valve’ for pubertal growth spurts in mandible. Maxillary intercanine width adjusts to the mandibular dentition as it is brought forward. This is called ‘safety valve mechanism.’ Q. 8. Endochondral and intramembranous bone formation Ans. The process of bone formation occurs by two basic methods: i. Endochondral bone formation ii. Intramembranous bone formation. i. Endochondral ossification (cartilaginous ossification/indirect ossification/endochondral bone formation) In this type of osteogenesis the bone formation is preceded by formation of a cartilaginous model, which is subsequently replaced by bone. Endochondral bone formation occurs as follows: At the site of bone formation; the condensation of mesenchymal cells takes place and some of them differentiate into chondroblasts and lay down hyaline cartilage. Orthodontics-Part-I-2013.indd 16 The cartilage is surrounded by a membrane called perichondrium, which is highly vascular and contains osteogenic cells. The intercellular substance surrounding the cartilage cells becomes calcified due to an enzyme alkaline phosphatase secreted by the cartilage cells. The cartilage cells are deprived of nutrition leading to their death. This results in the formation of empty spaces called primary areolae. The blood vessels and osteogenic cells from the perichondrium invade the calcified cartilaginous matrix, which is now reduced to bars or walls due to eating away of the calcified matrix. This leaves large empty spaces between the walls called secondary areolae. The osteogenic cells of perichondrium become osteoblasts, arrange themselves along the surface of these bars of calcified matrix and lay down osteoid, which later becomes calcified to form a lamella of bone. The calcified matrix of cartilage acts as a support for bone formation and layers of osteoid are secreted one upon other. The entire process of endochondral ossification is continuous and repetitive. Importance of endochondral ossification Cartilage behaves like a soft tissue, and growth takes place both by interstitial growth and appositional growth. Cartilage can grow in heavy pressure areas, as it is a pressure-adapted tissue unlike bone, e.g. cranial base. Linear growth takes place allowing lengthening of bones. ii. Intramembranous bone formation In this case, the formation of bone is not preceded by formation of a cartilaginous model. Instead, bone is laid down directly in a fibrous membrane. The intramembranous bone is formed in the following manner: At the site of bone formation, mesenchymal cells become aggregated and some of them lay down bundles of collagen fibres. Some mesenchymal cells enlarge and form osteoblasts, which secrete a gelatinous matrix called osteoid around the collagen fibres. The osteoid is converted into bone lamella by deposition of calcium salts in it; and now the osteoblasts move away from the lamellae and a new layer of osteoid is secreted, which also gets calcified. Some of the osteoblasts get entrapped between two lamellae. They are called osteocytes. Q. 9. Growth site versus growth centre Or Distinguish between growth centre and growth site by giving examples. 12/3/2013 2:49:11 PM
  • Topic wise Solved Questions of Previous Years 17 Ans. Various theories of growth are based on the growth centres. Growth sites do not control the overall growth of the bone. Differences between growth site and centre are as follows: Theories of growth are not based on growth site. The overall growth of the bone is controlled by growth centre. Growth site Growth centre It is any location or site where growth takes place. It is a location or place where genetically controlled growth takes place. Q. 10. Expanding ‘V’ principle It is a region where periosteal or sutural bone formation and remodelling resorption adaptive to environment occurs. It is a place of ossification with tissue-separating force. Ans. Sites of growth does not continue to grow when transplanted to another area. Centres of growth continue to grow when transplanted to another area. It markedly responses to external influences. Its response to external influence is less whereas response to functional needs is more. It is the place where exaggerated growth takes place but does not cause growth of the whole bone. It causes growth of the major part of the bone. All growth sites are not growth centres. All growth centres are growth sites. Expanding ‘V’ principle is one of the concepts/theories related to craniofacial growth, put forward by Enlow. According to Enlow’s expanding ‘V’ principle many facial bones or parts of bone have a ‘V’-shaped pattern of growth. In these bones the growth movements and enlargement occurs toward the wide ends of the ‘V’ as a result of differential deposition and selective resorption of bone. Bone deposition occurs on the inner side of the wide end of the ‘V’ and bone resorption on the outer surface. Deposition also takes place at the ends of the two arms of the ‘V’, resulting in growth movement towards the ends. In a number of regions such as the base of the mandible, ends of long bones, mandibular body, palate, etc., the ‘V’ pattern of the growth occurs. SHORT NOTES Q. 1. Growth spurts Or Growth spurts and two clinical importance Or Prepubertal growth spurt Ans. Growth does not take place uniformly at all times. There seems to be periods when a sudden acceleration of growth occurs. This sudden increase in growth is termed growth spurt. The timing of the growth spurts differs in boys and girls as follows: i. Just before birth ii. One year after birth iii. Mixed dentition growth spurt (boys 8–11 years and girls 7–9 years) iv. Prepubertal growth spurt (boys 14–16 years and girls 11–13 years). Clinical importance Knowledge of growth spurts is essential for successful treatment planning in orthodontics. Orthodontics-Part-I-2013.indd 17 Growth modulation by means of functional and orthodontic appliances elicits better response during growth spurts. Q. 2. Growth sites Ans. Growth site is any location or site where growth takes place. It is a region where periosteal or sutural bone formation, remodelling and resorption adaptive to environment occurs. Sites of growth do not continue to grow when transplanted to another area. They markedly respond to external influences. They are the places where exaggerated growth takes place; but they do not control the overall growth of the bone. All growth sites are not growth centres. Q. 3. Growth curve Or Scammon’s growth curves Or 12/3/2013 2:49:11 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 18 Enumerate various tissues for which Scammon’s growth curves are plotted. Ans. Scammon’s growth curve indicates that growth rate of different tissues is different at different ages. Example: The various tissues for which Scammon’s growth curve is plotted is lymphoid tissue, neural tissue, general or visceral tissue, and genital tissue. Lymphoid tissue proliferates rapidly in late childhood to almost 200% of adult size. By 18 years it undergoes involution to reach adult size. Neural tissue grows very rapidly and almost reaches adult size by 6–7 years of age; after that a very little growth occurs in neural tissue. General or visceral tissue exhibits ‘S’-shaped curve, which indicates rapid growth up to 2–3 years of age followed by slow phase between 3 and 10 years of age, followed again by rapid phase of growth occurring after 10th year and terminating by 18–20 years. Genital tissue shows negligible growth until puberty. They grow rapidly at puberty reaching adult size after which growth ceases. Q. 4. Capsular matrix Ans. Capsular matrix is a component of functional matrix. It has neurocranial capsule and orofacial capsule. Each of the neurocranial capsule and orofacial capsule is an envelope that contains series of functional cranial components, which as a whole is sandwiched between two covering layers. The alterations in special position of skeletal units is brought about by the expansion of these capsules with in which the respective bones arise, grow and are maintained. The skeletal units are passively and secondarily moved in space, as their enveloping capsule is expanded. This kind of translative growth is not brought about by deposition and resorption. Q. 5. Functional matrix theory Ans. Functional matrix hypothesis was put forward by Melvin Moss based on the work of van der Klaauw. The theory is simply stated as, ‘there is no direct genetic influence on the size, shape or position of skeletal tissues, only the initiation of ossification. All skeletogenic activity is primarily based upon the functional matrices.’ Functional cranial component is divided into functional matrix and skeletal unit; functional matrix comprises Orthodontics-Part-I-2013.indd 18 all the tissues, organs and functioning spaces as a whole, while skeletal unit comprises skeletal tissues related to specific function matrix. It was demonstrated that the origin, growth and maintenance of the skeletal unit depends almost exclusively upon its functional matrix. Clinical implications of functional matrix theory The forced application by orthodontic appliances tends to alter the functional matrix. Alteration of periosteal functional matrix produces changes in microskeletal unit while the alteration of capsular functional matrix produces changes in macroskeletal unit. Q. 6. Methods of measuring or studying growth Ans. Various methods of measuring growth are as follows: A. Proffit’s classification B. Moyer’s classification. A. Proffit’s classification Measurement approaches i. Anthropometry ii. Craniometry iii. Cephalometry iv. Arcial growth v. Logarithmic spiral vi. Finite element analysis B. Moyer’s classification i. ii. iii. iv. Experimental approaches Vital staining Radioactive tracer Autoradiography Implant radiography i. Quantitative method a. Direct measurements, e.g. craniometry, vital staining, etc. b. Indirect measurements, e.g. study casts, radiographs, etc. ii. Observations iii. Rating and ranking iv. Opinions. Q. 7. Twin studies Ans. In twin study, twins are compared. Comparing monozygotic twins with dizygotic twins is the best way to determine the extent of genetic effect on malocclusion. The heritability of malocclusion can be determined by comparing the ordinary siblings, monozygotic twins and dizygotic twins. In case of monozygotic twins, any change in occlusion or features could be attributed to environmental factors as both of them have similar DNA, whereas in dizygotic twins interplay of genetic and environmental factors is responsible. 12/3/2013 2:49:11 PM
  • Topic wise Solved Questions of Previous Years 19 Q. 8. Neurotrophism Ans. A non-impulse transmitting neural function that involves axoplasmic transport and provides for long-term interaction between neurons and innervated tissues that homeostatically regulate the morphological, compositional and functional integrity of those tissues is known as neurotrophism. Presently, the nature of neurotrophic substances and the process of their introduction into the target tissue is unknown. The various types of neurotrophic mechanisms are: i. Neuroepithelial trophism ii. Neurovisceral trophism iii. Neuromuscular trophism. Q. 9. Types of bone growth movements Or Cortical drift Ans. Drift and displacement are two basic methods of growth movements. Cortical drift A combination of bone deposition and resorption resulting in a growth movement towards the depositing surface is called cortical drift. It occurs in all the regions of growing bones, producing generalized enlargement as well as relocation of parts. Displacement The movement of the whole bone as a unit is known as displacement. It can be of two types: primary or secondary. i. Primary displacement: If a bone gets displaced as a result of its own growth, it is known as primary displacement. ii. Secondary displacement: If a displacement of bone occurs as a result of growth and enlargement of adjacent bone, it is known as secondary displacement. Q. 10. Growth trends Ans. Three types of growth trends enumerated by Tweed are as follows: i. Type A: Maxilla and mandible grow in unison, both downwards and forwards. ANB shows no change. ii. Type B: Maxilla grows more rapidly than mandible. ANB angle increases. iii. Type C: Mandible grows faster than maxilla. Decrease in ANB angle. Orthodontics-Part-I-2013.indd 19 These growth trends are helpful in planning retention for individual orthodontic cases. Q. 11. Growth centres Ans. Growth centre is a location or place where genetically controlled growth takes place. These are places of ossification with tissue-separating force and cause growth of the major part of the bone. Centres of growth continue to grow when transplanted to another area. Their response to external influence is less, whereas response to functional needs is more. All growth centres are growth sites. The overall growth of the bone is controlled by growth centre. Q. 12. Differential growth Ans. Human throughout life body does not grow at the same rate; different organs grow at different rates to a different amount and at different times. This is known as differential growth. The concepts of differential growth are more clearly understood by two important aspects of growth: i. Cephalocaudal gradient of growth ii. Scammon’s curve of growth i. Cephalocaudal gradient of growth. An axis of increased growth gradient extending from head towards the feet is called ‘cephalocaudal growth.’ In fetal life, head constitutes 50% of total body length while limbs are primitive (30%). At the time of birth, head constitutes 25–30% and there is increased growth of body and limbs. In an adult, the head constitutes only 12%, while limbs accounts to 50%. These changes in the pattern of growth are because of cephalocaudal gradient. Scammon’s growth curve indicates that growth rate of different tissues are different at different ages. Example: The various tissues for which Scammon’s growth curve is plotted are lymphoid tissue, neural tissue, general or visceral tissue, and genital tissue. Q. 13. Methods of gathering growth data Ans. The various methods of gathering growth data are as follows: i. Longitudinal studies ii. Cross-sectional studies iii. Semilongitudinal studies. 12/3/2013 2:49:11 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 20 The physical growth can be studied by a number of ways: i. Opinion ii. Observations iii. Ratings and rankings. Quantitative measurements: A scientific approach to study growth is based on accurate measurements, which are of three types: i. Direct data ii. Indirect data iii. Derived data. Q. 14. Enumerate the peak periods of postnatal growth. Ans. The peak periods of postnatal growth are as follows: i. One year after birth ii. Mixed dentition growth spurt (boys 8–11 years and girls 7–9 years) Topic 3 iii. Prepubertal growth spurt (boys 14–16 years and girls 11–13 years). Q. 15. Enumerate various theories of growth. Ans. Based on the expression of intrinsic genetic potential various theories of craniofacial growth are: i. Genetic theory by Brodie ii. Sutural dominance theory by Sicher iii. Cartilaginous theory by Scott iv. Functional matrix theory by Melvin Moss v. van Limborgh’s theory. Other concepts/theories related to craniofacial growth are: i. Hunter and Enlow’s growth equivalent concept ii. Petrovic’s cybernetic theory. GROWTH AND DEVELOPMENT OF CRANIAL AND FACIAL STRUCTURES LONG ESSAYS Q. 1. Describe in detail about prenatal and postnatal growth of mandible. Or Discuss prenatal and postnatal growth of mandible and its clinical implications in orthodontics. Or Followed by Mesenchymal condensation forming the first arch (mandibular arch) Define growth and development. Explain the postnatal growth of mandible. Ans. Prenatal growth phases are as follows: i. Period of ovum (from fertilization to 14th day) ii. Period of embryo (from 14th to 56th day) iii. Period of fetus (56th day to birth). Prenatal growth of mandible Mandible is derived from ossification of an osteogenic membrane formed from ectomesenchymal condensation at around 36–38 days Resulting intramembranous bone lies lateral to Meckel’s cartilage of 1st arch (mandibular arch) First structure to develop in primordium of lower jaw is At 6th week of IU life Mandibular division of V nerve (function: presence of nerve is postulated as being necessary to induce osteogenesis by production of neurotrophic factors.) Orthodontics-Part-I-2013.indd 20 In the region of bifurcation of inferior alveolar nerve into mental and incisive branches, a single ossification centre for each half of the mandible arises. 12/3/2013 2:49:11 PM
  • Topic wise Solved Questions of Previous Years 21 The condyles are low and at the position of the occlusal plane. The symphyseal suture has not ossified. During 7th week of IU life The bone begins to develop lateral to Meckel’s cartilage and continues until the posterior aspect is covered by the bone. Ossification stops at the point that later becomes the mandibular lingula, from where Meckel’s cartilage continues into middle ear and develops into auditory ossicles, i.e. malleus and incus. The remaining part of the Meckel’s cartilage continues on its own to form the sphenomandibular ligament and the spinous process of the sphenoid bone, which are remnants of it. Between 8th and 12th weeks of IU life. There is marked acceleration of mandibular growth and as a result mandibular length increases; the external auditory meatus appears to move posteriorly. Between 10th and 14th weeks of IU life. Secondary accessory cartilages appear to form the head of the condyle, part of the coronoid process and mental protuberance. Soon the growing intramembranous ossification fuses the coronoid process to the ramus. The ossification of the ramus proceeds and the condyle is soon fused to the mandible at about 16 weeks. Meckel’s cartilage persists until as long as 24th week of IU life before it disappears. Postnatal growth of mandible Among all the facial bones, the mandible undergoes largest amount of growth postnatally and also exhibits the largest variability in morphology. Mandibular growth in the postnatal life shows integration of the periosteal and capsular matrices of functional matrix theory by Moss. Capsular matrix involves the oropharyngeal functional spaces and the mandible grows according to the functional needs of the particular functional system. The process of surface remodelling usually involves the activity of the periosteal matrix, i.e. muscle fibres. Mandible at birth Mandible at birth is much smaller in size and varies in shape from the adult form. The infant mandible has a short, more or less horizontal ramus with obtuse gonial angle. Orthodontics-Part-I-2013.indd 21 Growth in the first year It involves growth at the symphyseal suture and lateral expansion in the anterior region to accommodate the erupting anterior teeth. The mental foramen is directed at right angle to the surface of the corpus. There is increased bone deposition in the posterior surface of the ramus of the mandible. The infant mandible is suited for the suckling activity since the condyle and the glenoid fossa is flat, which helps in the anteroposterior movement of the mandible. Mandible in the adult/concept of V principle The adult mandible differs from the mandible of an infant in which: the ramus is longer and the gonial angle is less obtuse. the bone is larger on the whole and the condyle is welldeveloped. All these changes take place in the growth of the mandible in the form of an expanding V. Because of its horseshoe shape, it is easier to visualize mandible as the V-shaped bone than the maxilla. ‘V’ principle of growth According to this principle growth of mandible in length, width and height is as follows: Length The growth of the mandible in length anteroposteriorly is by the deposition of bone at the posterior border of the ramus and resorption at the anterior surface, which helps to lengthen mandible so that the anterior part of the ramus is occupied by the posterior part of the body in the future and accommodates the developing permanent molars. As the articulation of the condyle to the glenoid fossa is constant, the anterior displacement causes displacement of the mandible anteriorly as it grows posteriorly. As the mandible grows anteriorly, the opening of the mental foramen faces backward so that the neurovascular bundle leaves the foramen directed backwards. There is corresponding surface remodelling at the anterior border with deposition in the posterior surface of the symphysis, resorption in the superior part of the anterior surface and deposition in the inferior aspect. Width There is deposition in the lateral surface of the ramus and resorption on the lingual surface of mandible below the mylohyoid ridge. In contrast, the coronoid process undergoes apposition at the medial surface and resorption at the lateral surface. This expands the mandible like a V. 12/3/2013 2:49:11 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 22 The condyle undergoes reduction of bone on the lateral aspect of neck; and deposition corresponding to the V principle makes the condyle longer at the neck. Following the V principle, the interramal distance is efficiently increased by the growth of mandible, which helps the mandible to keep pace with the growth of the cranial base. The mandible, which is often retrognathic in the newborn, assumes an orthognathic relation with the maxilla during adulthood due to the growth of the bone in length. The condylar cartilage contributes little, if any, to the growth and does not act as primary growth centre. In patients with ankylosis of the temporomandibular joint, the mandible is found to grow to normal length. The muscular processes of the mandible like angle, coronoid and condylar processes are under the influence of the periosteal matrix. Height In the alveolar process, height increases well with eruption of teeth. Bone deposition taking place in the lower border of mandible also contributes to increase in height of the mandible. Rotation of mandible Bjork used implants to study the growth pattern of mandible and found that mandible undergoes growth rotation. It was found that though mandible undergoes rotation the effects seen are minimal due to external compensation. It was concluded that the growth of mandible is largely influenced by the functional matrices; and condylar cartilage has little influence in its overall growth. Summary of mandibular growth Length increases by: i. Surface apposition at posterior border of ramus and resorption at anterior border ii. Deposition at bony chin iii. Growth at condylar cartilage. Height increases by: i. Surface apposition at alveolar border ii. Apposition at the lower border of mandible iii. Growth at the condylar cartilage. Width increases by: i. Sutural growth up to 1st year postnatally ii. Later surface apposition at outer surface. Growth sites in mandible are: i. Mandibular condyle ii. Posterior border of ramus iii. Alveolar process iv. Lower border of mandible v. Suture. Orthodontics-Part-I-2013.indd 22 Q. 2. Define growth and development. Discuss prenatal growth of maxilla. Ans. Growth has been defined by various clinicians in different ways as follows: JS Huxley—‘The self-multiplication of living substance.’ Krogman—‘Increase in size, change in proportion and progressive complexity.’ Todd—‘An increase in size.’ Merdith—‘Entire series of sequential anatomic and physiologic changes taking place from the beginning of prenatal life to senility.’ Moyers—‘Quantitative aspect of biologic development per unit of time.’ Moss—‘Change in any morphological parameter which is measurable.’ Development is defined in simple words as ‘progression towards maturity.’ According to Melvin Moss, “development can be considered as a continuum of causally related events from the fertilization of ovum onwards.” Prenatal growth of maxilla Maxillae, a pair of bones on either side of the middlethird of the face, formed by intramembranous bone formation. Due to its more cranial location, maxilla is ahead of mandible in growth, generally. The cephalocaudal gradient of growth of maxilla closely follows the neural growth curve in the Scammon’s curves. Stages of prenatal growth of craniofacial region The prenatal craniofacial growth develops in three stages: a. The period of the ovum from fertilization till 2nd week b. The period of embryo from 2nd to 8th week c. The period of fetus from the 9th week till birth. The tissues of the face, both hard and soft tissues, are of neural crest cell origin, also called ectomesenchymal origin. The neural crest cell gives rise to diverse structures—both near the site of its origin and at remote sites. In the head and neck region the neural crest cells give rise to facial processes, branchial arches and their cartilages, etc. Frontonasal process The head begins to take shape at around 21 days after conception. The migrating neural crest cells when encounter the lens placode form two streams. The anterior stream of cells forms the mesenchyme of the frontonasal process and the posterior stream migrates to form the structures of the branchial arches. 12/3/2013 2:49:11 PM
  • Topic wise Solved Questions of Previous Years 23 Most of the development of the face takes place between 3rd and 8th week of IUL. At around 4th week of IUL, the branchial arches begin to develop. Branchial arches The branchial arches, developing during the late somite period, are formed from the mesoderm of the ventral foregut. There are five pairs of branchial arches, the fifth being transitory. The first arch is the mandibular arch and the second arch is the hyoid arch. The jaws of the face, namely, maxilla and mandible, are derived from the first arch. In the meanwhile, the frontonasal process of the forebrain just above the stomodeum develops bilateral thickenings called nasal placodes. In the middle, there is invagination of the placode to form nasal pits; on both sides of them there are elevations that are medial and lateral nasal processes. Maxillary process By around 4th week of IUL facial process arises from the first arch, which corresponds to the mandibular processes. Later, ventromedially two more swellings grow from the mandibular processes called the maxillary processes. By about 6th week the processes of the face are easily discernible. The stomodeum is bound by the frontonasal process above, the mandibular process below and the sides being occupied by the maxillary processes. The maxillary process grows ventromedially towards the nasal processes. The maxillary process fuses with the lateral nasal process and migrates medially to contact the inferolateral side of the medial nasal process. The maxillary and the medial nasal processes are initially separated by the epithelial nasal fin, which soon degenerates so that the mesenchyme of the two processes fuses. The maxillary and mandibular processes fuse at the sides to form the cheek tissue. The lateral nasal process forms the ala of the nose. The medial nasal process of both sides fuse to form the globular process in the middle, which gives rise to the tip of the nose, columella, philtrum, labial tuberculum of the upper lip, frenulum and entire primary palate. The maxillary process forms the alveolus, which bears teeth distal to the canines and the secondary palate. The area of fusion of the maxillary and mandibular processes forms the commissural corners of the mouth. As the two processes grow towards the fellow of the opposite side, the stomodeum is narrowed. Ossification centres of maxilla Maxilla develops by intramembranous ossification. A primary ossification centre appears at about early 8th week at the termination of the infraorbital nerve situated just above the canine tooth lamina. There are two centres for each maxilla. Orthodontics-Part-I-2013.indd 23 Secondary cartilages appear at the end of the 8th week in the regions of the zygomatic and alveolar processes that ossify and fuse with the primary centre. Around 8th week, two ossification centres appear in the region of the premaxilla on each side. The centres rapidly merge with the primary centres and are overshadowed by the growth of the primary centres. Q. 3. Explain how maxilla increases in width, length and height. Or Explain in detail about postnatal growth and development of maxilla. Ans. Postnatal growth of maxilla The development and growth of maxilla is completed early when compared to the mandible. The growth of maxilla especially in width closely follows the neural growth curve more than the general growth curve in the Scammon’s curve. Growth of maxilla Growth of maxilla occurs by the following processes: 1. Displacement or translation Displacement or translation of a bone is the process by which specific local areas come to occupy new actual positions in succession as the entire bone enlarges. It may be active or passive. Maxilla is attached to the cranial base; hence the growth of the cranial base has a direct bearing on the nasomaxillary growth. A passive or secondary displacement of the nasomaxillary complex occurs in a downward and forward direction as the cranial base grows. This is a secondary type of displacement, the nasomaxillary complex is simply moved anteriorly as the middle cranial fossa grows in that direction. It is an important growth mechanism during the primary dentition period, but becomes less important as growth of cranial base slows down. Active translation takes place when the growth at the tuberosity of the maxilla pushes the maxilla forward. A primary type of displacement is seen in a forward direction, which results in the whole maxilla being carried anteriorly. The amount of this forward displacement equals the amount of posterior lengthening. This is a primary type of displacement as the bone is displaced by its own enlargement. 2. Growth at the sutures by connective tissue proliferation The maxillae articulate with the surrounding bones of cranium and cranial base with the help of number of 12/3/2013 2:49:11 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 24 sutures like the zygomaticomaxillary, frontomaxillary, pterygopalatine and zygomaticotemporal sutures, etc. According to Sicher, growth at these paired parallel sutures will move the maxilla downward and forward. It is only secondary and not a primary mechanism. As growth of the surrounding soft tissue occurs, the maxilla is carried downwards and forward leading to opening up of space at the sutural attachments. New bone is now formed on either side of the sutures leading to the overall increase in size of the bones on either side. Hence, a tension-related bone formation occurs at the sutures. 3. Remodelling In addition to the growth occurring at the sutures, simultaneous resorption and deposition moves the surfaces of the maxilla while maintaining the integrity and basic shape of the bone. Remodelling by bone deposition and resorption occurs to bring about: a. Increase in size b. Change in shape of bone c. Change in functional relationship. Maxillary growth matures first in width followed by the depth and length. It would be easier to discuss the growth of maxilla in the same order. a. Maxillary width The floor of the orbit faces superiorly, laterally and anteriorly. Growth proceeds in this direction by deposition and resorption on the lateral surface of the orbital rim. Resorption occurs on the lateral surface of the orbital rim leading to lateral movement of the eye ball. To compensate, there is bone deposition on the medial rim of the orbit and on the external surface of the lateral rim. Mid-palatal suture is active till 15 years; but it cannot be generalized. Due to sutural growth there is bone fill in the mid-palatal area and resorption in the lateral aspect. The entire wall of the sinus except the mesial wall undergoes resorption. This results in increase in size of the maxillary sinus. In the zygomatic process and the zygomatic arch, it is more complex. There is deposition on the posterior and lateral aspects and resorption on the anterior and medial surfaces. Thus the zygomatic bone moves in a posterior direction. The face enlarges in width by bone formation on the lateral surface of the zygomatic arch and resorption on its medial surface. The nasal part of the maxilla faces in an anterior, lateral and superior direction. The growth proceeds in the same Orthodontics-Part-I-2013.indd 24 direction. There is surface removal of bone from the periosteum lining the inner aspect of the nasal cavity and deposition on the endosteal surface. This allows expansion of the nasal cavity. b. Anteroposterior depth Zygomatic bone moves posteriorly and laterally by deposition in the posterior and lateral surface and resorption in the medial surface. Bone deposition occurs along the posterior margin of the maxillary tuberosity. This causes lengthening of the dental arch and enlargement of the anteroposterior dimension of the entire maxillary body. This helps to accommodate the erupting molars. The anterior nasal spine prominence increases due to bone deposition. In addition, there is resorption from the periosteal surface of labial cortex. As a compensatory mechanism, bone deposition occurs on the endosteal surface of the labial cortex and periosteal surface of the lingual cortex, and the maxilla moves forward. The zygomatic bone moves in a posterior direction to keep its relation with the maxilla. This happens by resorption in the anterior surface and deposition in the posterior surface. c. Maxillary height Bone resorption is seen on the floor of the nasal cavity. To compensate, there is bone deposition on the palatal side. Thus a net downward shift occurs leading to increase in maxillary height. As the teeth start erupting, bone deposition occurs at the alveolar margins. This increases vertical height of the maxilla and depth of the palate. This increase is seen as long as the teeth erupt. This contributes to early increase in the height of maxilla and accounts for about 40% increase in the maxillary height. Maxillary growth can be summarized as follows: Length increases by—sutural growth and the surface apposition at maxillary tuberosity. Width increases by—growth at the median palatine suture and apposition at zygomatic bone. Height increases by—sutural growth, surface apposition and alveolar growth. Growth sites in maxilla: i. Maxillary tuberosity ii. Sutures iii. Alveolar border iv. Nasal septum v. Lateral walls. 12/3/2013 2:49:11 PM
  • Topic wise Solved Questions of Previous Years 25 SHORT ESSAYS Q. 1. Development of palate Ans. The palate is formed by contributions of the following maxillary process: i. Palatal shelves of the maxillary process ii. Frontonasal process. The frontonasal process gives rise to the premaxillary region while the palatal shelves form the rest of the palate. As the palatal shelves grow medially, their union is prevented by the presence of the tongue. Thus, initially the developing palatal shelves grow vertically downwards towards the floor of the mouth. During the 7th week of intrauterine life withdrawal of tongue from between palatal shelves aids in transformation of their position from a vertical to a horizontal direction. By 8½ weeks of intrauterine life the two palatal shelves are in close approximation with each other, which are initially covered by an epithelial lining. As they join, the epithelial cells degenerate. The connective tissues of the palatal shelves intermingle with each other resulting in their fusion. The entire palate does not contact and fuse at the same time. Initially contact occurs in the central region of the secondary palate posterior to the premaxilla. From this point, closure occurs both anteriorly and posteriorly. The mesial edges of the palatal processes fuse with the free lower end of nasal septum and thus separates the nasal cavities from each other and the oral cavity. Ossification of the palate occurs from the 8th week of intrauterine life. The palate ossifies from a single centre derived from the maxilla. The most posterior part of the palate does not ossify and forms the soft palate. The midpalatal suture ossifies by 12–14 years. Postnatal growth of the palate follows the concept of expanding ‘V’ by Enlow. It is a more complex process. It is one of the best examples of the expanding ‘V’ principle. Growth at the suture by bone fill contributes more to the increase in width of the palate than remodelling. The width of the palate also increases by the growth of the alveolar process which diverges out. Many bones or parts of the bone are in the form of ‘V’. Bone deposition takes place on the inner side of ‘V’ and resorption takes place on the outer surface. If the outer surface of the expanding ‘V’ is taken, the periosteal surface can be found to be lined with osteoclasts, and endosteal surface is found to be lined with osteoblasts. Orthodontics-Part-I-2013.indd 25 In young child the maxillary arch and the nasal floor are very close to the inferior orbital rim. By deposition on the palatal periosteal surface and resorption on the nasal floor, the palate comes to occupy a lower position. When viewed in the cross-section, the deposition of the bone occurs along the whole of the periosteal surface of the palate in such a way that the bone expands in a lateral direction and also downwards. The nasal floor due to resorption increases in volume and descends down from the level of infraorbital rim. In conjunction with the ‘V’ principle, half of the external surface involved in this growth is depository and other half is resorptive; thus, half of the bone tissue of the palate is endosteal and other half is periosteal. The same concept is seen even in the anteroposterior growth of the palate or midsagittal section of the palate. There is deposition on the palatal surface and resorption along the anterior surface or incisor area and superior surface, expanding the palate like a ‘V’. Q. 2. Describe the developmental defects of maxilla. Ans. The developmental defects of maxilla are as follows: The most prominent defect in the development of maxilla is the cleft lip—either unilateral or bilateral. The cleft lip can be complete or partial. The most common is unilateral cleft lip (1 in 800 births). Bilateral cleft lip is rare and produces a protuberant, freehanging middle part of the lip. The cleft lip occurs due to failure of the fusion of maxillary and medial nasal processes. The failure of fusion of the medial nasal processes produces the midline cleft—the ‘true hare lip’, which is exceedingly rare. Lateral facial cleft or oblique facial cleft is occasionally seen in condition of failure of fusion of lateral nasal process with the maxillary process. Cleft lip/palate and other facial clefts develop during the period of organ formation in the craniofacial development. This approximates to about 28–55 days of IUL. Over fusion of the maxillary and mandibular processes leads to a small mouth called microstomia. Q. 3. Postnatal growth and development of the mandible. Ans. Postnatal growth of mandible is as follows: 12/3/2013 2:49:11 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 26 Among all the facial bones the mandible undergoes the largest amount of growth postnatally and also exhibits the largest variability in morphology. Mandible at birth Mandible at birth is much smaller in size and varies in shape from the adult form. The symphyseal suture has not ossified. Growth in the first year It involves growth at the symphyseal suture and lateral expansion in the anterior region to accommodate the erupting anterior teeth. There is increased bone deposition in the posterior surface of the ramus of the mandible. ‘V’ principle of growth According to this principle, growth of mandible in length, width and height is as follows: Length The growth of the mandible in length anteroposteriorly is by the deposition of bone at the posterior border of the ramus and resorption at the anterior surface, which helps to lengthen mandible so that the anterior part of the ramus is occupied by the posterior part of the body in the future and accommodates the developing permanent molars. Width There is deposition on the lateral surface of the ramus and resorption on the lingual surface of mandible below the mylohyoid ridge. In contrast, the coronoid process undergoes apposition at the medial surface and resorption at the lateral surface. This expands the mandible like a ‘V’. Following the ‘V’ principle, the interramal distance is efficiently increased by the growth of mandible, which helps the mandible to keep pace with the growth of the cranial base. Height Alveolar process height increases well with eruption of teeth. Bone deposition taking place in the lower border of mandible also contributes to increase in the height of the mandible. Q. 4. Spheno-occipital synchondrosis Ans. Synchondroses are defined as the bands of cartilage present at the junction of various bones during the bone formation stage. These synchondroses form important growth sites in the base of skull. Cranial base grows by cartilaginous growth in the synchondroses, which later gets calcified. Orthodontics-Part-I-2013.indd 26 Types of synchondroses These are classified into four subtypes: i. Intersphenoidal synchondroses—occurs at birth ii. Intraoccipital synchondroses—occurs at 3–5 years iii. Spheno-occipital synchondroses—occurs at 20 years iv. Sphenoethmoidal synchondroses—exact age is not known. Spheno-occipital synchondrosis Spheno-occipital synchondrosis is the cartilaginous junction between the sphenoid and the occipital bones, is active up to the age of 12–15 years and becomes fused by the age of 20 years. It is responsible for most of the lengthening of cranial base between foramen magnum and sella turcica, and is the important growth site of cranial base during childhood. Cranial base lengthening is contributed by elongation of synchondroses in combination with drift and remodeling. As endochondral bone growth occurs at the spheno-occipital synchondrosis, the sphenoid and occipital bones move apart. At the same time new endochondral bone is laid down in the medullary region and cortical bone is formed in endosteal and periosteal regions. Thus, sphenoid and occipital bones increase in length and width. Cartilage unlike bone is a pressure-adapted tissue and can grow in heavy-pressure areas, e.g. cranial base. Clinical implications Spheno-occipital synchondroses are responsible for most of the lengthening of cranial base between foramen magnum and sella turcica. It is the major contribution of endochondral growth till 20 years. Elongation of synchondroses in combination with drift and remodelling contribute to cranial base lengthening. Q. 5. Sutural growth of maxilla Ans. The maxilla is connected to the cranium and cranial base by a number of sutures. These sutures include: i. Frontonasal suture ii. Frontomaxillary suture iii. Zygomaticotemporal suture iv. Zygomaticomaxillary suture v. Pterygopalatine suture. These sutures are all oblique and more or less parallel to each other. This allows the downward and forward repositioning of the maxilla, as growth occurs at these sutures. As growth of the surrounding soft tissue occurs, the maxilla is carried downwards and forward. This leads to opening up of space at the sutural attachments. 12/3/2013 2:49:11 PM
  • Topic wise Solved Questions of Previous Years 27 New bone is now formed on either side of the suture. Thus, the overall size of the bones on either side increases. Hence, a tension-related bone formation occurs at the sutures. Q. 6. Development of tongue ❍ ❍ ❍ Ans. At approximately 4 weeks the tongue appears in embryo in the form of two lateral lingual swellings and one median swelling—the tuberculum impar. These three swellings originate from the first pharyngeal arch (Fig. 3.1). A second median swelling—the copula or hypobranchial eminence—is formed by mesoderm of the second, third and part of the fourth arch. A third median swelling is formed by the posterior part of the fourth arch. Lateral lingual swelling Tuberculum impar Terminal sulcus Body of tongue I II I III Copula (hypobranchial eminence) Epiglottal swelling Foramen cecum IV II III Laryngeal orifice 5 Arytenoid swellings Palatine tonsil IV Root of tongue 5 Epiglottis Fig. 3.1 Pharyngeal arches involved in development of tongue. As the lateral swellings increase in size they overgrow the tuberculum impar and merge, forming the anterior twothirds or body of the tongue; sensory innervation to this area is by the mandibular branch of the trigeminal nerve. The posterior part or root of the tongue originates from the second, third and part of the fourth pharyngeal arch. The sensory innervation to this part of the tongue is supplied by the glossopharyngeal nerve indicating that tissue of the third arch overgrows that of the second. The extreme posterior part of the tongue is innervated by the superior laryngeal nerve, reflecting its development from the fourth arch. Some of the tongue muscles probably differentiate in situ; but most are derived from myoblasts originating in occipital somites. Thus, tongue musculature is innervated by the hypoglossal nerve. The general sensory innervation of the tongue is easy to understand: Orthodontics-Part-I-2013.indd 27 The body is supplied by the trigeminal nerve—the nerve of the first arch. The root is supplied by the glossopharyngeal and vagus nerves—the nerves of the third and fourth arches, respectively. Special sensory innervation (taste) to the body of the tongue is provided by the chorda tympani branch of the facial nerve. Q. 7. Mechanisms of bone growth Ans. Mechanisms of bone growth The growth of any bone follows certain basic processes like remodelling and growth movements caused by drifts and displacement. Remodelling Remodelling is the differential growth activity necessary for bone shaping. It is not a uniform process. The process of remodelling is differential, e.g. if deposition takes place on the outer/periosteal surface of bone then resorption takes place in the endosteal surface. Remodelling is the basic growth process providing regional changes in the shape, dimensions and proportions of bone. It also performs regional adjustments in the bone to the changing functional demands. Growth movements Two types of growth movements occur during the enlargement of the cranial bones. They are drift and displacement. Drift: It is the movement of the bone surface caused by deposition and resorption towards the depository surface. It is otherwise called transformation. Displacement: It is the growth of the bone as a whole unit so that the bone is taken away from its articulation with other bones. It is otherwise called translation. Displacement is of two kinds: i. Primary or active: Where the movement is due to the growth of the bone itself, e.g. growth of maxilla at tuberosity region. ii. Secondary displacement: It is the movement of one bone due to the growth of other bones or translation within the capsule. It is passive. Example: Growth of maxilla due to growth at the sphenooccipital synchondrosis. 12/3/2013 2:49:11 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 28 SHORT NOTES Q. 1. Define synchondrosis Or Enumerate types of synchondrosis. Ans. Synchondroses are defined as the bands of cartilage present at the junction of various bones during the bone formation stage. These synchondroses form important growth sites in the base of skull. Cranial base grows by cartilaginous growth in the synchondroses, which later gets calcified. Types of synchondroses They are classified into four subtypes: i. Intersphenoidal synchondroses—occurs at birth ii. Intraoccipital synchondroses—occurs at 3–5 years iii. Spheno-occipital synchondroses—occurs at 20 years iv. Sphenoethmoidal synchondroses—exact age is not known. Q. 2. Meckel’s cartilage Ans. The Meckel’s cartilage is the cartilage of the first branchial arch. Meckel’s cartilage appears bilaterally as cartilaginous bars; the anterior aspects of these two cartilages approaches each other near the midline, but do not fuse while posteriorly, they terminate in a bulbous structure called malleus. Malleus and incus are derivatives of Meckel’s cartilage. The part of the cartilage extending from the region of the middle ear to mandible disappears; but its sheath forms the ‘anterior ligament of the malleus’ and the ‘sphenomandibular ligament’. Q. 3. Enumerate the mechanisms of bone growth. Ans. Mechanisms of bone growth The growth of any bone follows certain basic processes like remodelling and growth movements. Remodelling Remodelling is the differential growth activity necessary for bone shaping. It is not a uniform process. It is the basic growth process providing regional changes in the shape, dimensions and proportions of bone. It also performs regional adjustments in the bone to the changing functional demands. Orthodontics-Part-I-2013.indd 28 Growth movements There are two types of growth movements: a. Drift: It is the movement of the bone surface caused by deposition and resorption towards the depository surface. It is otherwise called transformation. b. Displacement: It is the growth of the bone as a whole unit so that the bone is taken away from its articulation with other bones. It is otherwise called translation. Displacement is of two kinds: i. Primary or active displacement ii. Secondary displacement. Q. 4. Endochondral bone formation Ans. Endochondral bone is formed in a cartilagenous model; osteoblasts invade cartilage and replace it. The first step during endochondral bone formation is the differentiation of mesenchymal cells into chondrocytes. These chondrocytes form a rough model, which is enclosed by perichondral cells. Cartilage mass grows both by interstitial growth and by apposition. Cartilage cells undergo hypertrophy and their matrix begins to get calcified. The blood vessels penetrate the cartilage mass from the perichondrium during this time. These penetrating blood vessels carry undifferentiated mesenchymal cells along with them, which get converted into osteoblasts. Osteoblasts subsequently deposit bone and bone spicules are formed. Gradually the cartilage mass is replaced by bone. Endochondral bone formation is usually seen in areas where there are high levels of compression. Example: Cranial base and movable joints. Q. 5. Development of palate Ans. The primary palate is derived from the intermaxillary segment. The main part of the definitive palate is formed by two shelf-like outgrowths from the maxillary prominences known as palatine shelves, which appear in the 6th week of development and are directed obliquely downwards on each side of the tongue. During 7th week, the palatine shelves ascend to attain a horizontal position above the tongue and fuse, forming the secondary palate. Anteriorly the shelves fuse with the triangular primary palate, and the incisive foramen is the midline landmark between the primary and secondary plates. 12/3/2013 2:49:11 PM
  • Topic wise Solved Questions of Previous Years 29 At the same time as the palatine shelves fuse, the nasal septum grows down and joins with cephalic aspect of the newly formed palate. New bone is now formed on either side of the sutures leading to the overall increase in size of the bones on either side. Hence, a tension related bone formation occurs at the sutures. Q. 6. Nasal septal cartilage Q. 8. Butler’s field theory Ans. Nasal septum appears to be the primary factor in the displacement of nasomaxillary complex. During prenatal period, nasal septal cartilage lies behind the cranial base cartilages and is attached in front and below to premaxillary bone as well as vomer and posteriorly to mesethmoid cartilage. During postnatal development perpendicular plate of ethmoid bone ossifies from mesethmoid cartilage at birth. The perpendicular plate of ethmoid bone fuses with cribriform plate of ethmoid bone at 3 years of age. With this, the cranial components are fused with facial bony elements. Anterior part of the nasal septum remains cartilaginous throughout life. After the union of cranial and facial bony components, the nasal septum has very little effect on the facial growth. Q. 7. Sutural growth of maxilla The maxillae articulate with the surrounding bones of cranium and cranial base with the help of a number of sutures like the zygomaticomaxillary, frontomaxillary, pterygopalatine and zygomaticotemporal sutures, etc. According to Sicher, growth at these paired parallel sutures will move the maxilla downwards and forward. It is only secondary and not a primary mechanism. As growth of the surrounding soft tissue occurs, the maxilla is carried downwards and forward leading to opening up of space at the sutural attachments. 4 The human dentition is divided into four fields: incisor, canine, premolar and molar. The most distal tooth in each field is the most susceptible to changes or variations which include absence of tooth, variation in size, shape and structure. This is called Butler’s field theory. Examples: Lateral incisors, second premolars and third molars are the most variable in their group. Canine is the least variable tooth in the arch. Butler’s field theory does not apply in lower anterior region, where mandibular central incisor is more commonly missing than lateral incisor. Q. 9. How does an infant and an adult mandible differ from each other? Ans. Ans. Topic Ans. The infant mandible has a short, more or less horizontal ramus with obtuse gonial angle. The condyles are low and at the position of the occlusal plane. The adult mandible differs from the mandible of an infant in which: the ramus is longer and the gonial angle is less obtuse. the bone is larger on the whole and the condyle is welldeveloped. all these changes take place in the growth of the mandible in the form of an expanding ‘V’. DEVELOPMENT OF DENTITION AND OCCLUSION LONG ESSAYS Q. 1. Discuss the development of occlusion and its significance. Or Define normal occlusion. Describe normal occlusion in deciduous dentition and its further development till the age of 12 years. Describe the development of dentition and intra-arch tooth relationships from 6th to 12th year of a child’s life. Ans. Or Orthodontics-Part-I-2013.indd 29 Occlusal development can be divided into the following periods or stages: 12/3/2013 2:49:12 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 30 Predental period (birth to 6 months) Gum pads and their relationship Deciduous dentition period (6–2½ to 3½ years) i. Spring of anterior teeth ii. Primate/simian spaces iii. Shallow overjet/overbite iv. Vertical inclination of anterior teeth v. Deep bite (early stages) vi. Flush terminal plane Mix dentition period (6 years–12 years) First transition period Intertransition period Permanent dentition period (starts after shedding of last primary tooth) Second transition period i. Molar relation ii. Eruption sequence i. Emergence of 6 6 6 6 Incisal liability ii. Replacement of incisors A with 1 Ugly duckling stage Early mesial shift Leeway space iii. Replacement of CDE Late mesial shift Change of terminal planes PREDENTAL PERIOD Transverse Grooves This period extends from birth to 6 months of age after birth, i.e. 0–6 months. The neonate is without teeth for about 6 months of life. The alveolar arches of an infant at this time period are known as gum pads. The features of gum pads are as follows: They are pink in colour, firm in consistency and covered by dense layer of fibrous periosteum. They are horseshoe shaped and develop in two parts: i. Labiobuccal portion ii. Lingual portion. Dental Groove These two portions are separated by a groove called the dental groove (Fig 4.1). Lateral sulcus Dental groove Gingival groove Fig. 4.1 Maxillary gum pad. Orthodontics-Part-I-2013.indd 30 The gum pads are divided into 10 segments by transverse grooves. Each segment consists of one developing deciduous tooth sac. Lateral Sulcus The transverse groove between the canine and first deciduous molar segment is called the lateral sulcus. The lateral sulcus of mandibular arch is normally more distal to that of maxillary arch. The lateral sulci are useful in judging the interarch relationship of maxilla and mandible at very early stage. Upper and lower gum pads are almost similar to each other. Relationship of Gum Pads When upper and lower gum pads are approximated there is a complete overjet all around, as the upper gum pad is wider as well as longer than lower gum pad. Mandibular lateral sulci are posterior to maxillary ones. Class II pattern is exhibited, as maxillary gum pad being more prominent. Anterior open bite: This infantile open bite is considered normal. Contact occurs between the upper and lower gum pads in first molar region and a space exists between them anteriorly known as infantile open bite, which helps in sucking. 12/3/2013 2:49:12 PM
  • Topic wise Solved Questions of Previous Years 31 DECIDUOUS DENTITION PERIOD The deciduous dentition period extends from 6 months to 6 years of postnatal life. It starts with eruption of deciduous mandibular central incisors and completes with second deciduous molars coming into occlusion. The eruption of all primary teeth is completed by 2½–3 ½ years of age. The normal features of the ideal occlusion in the primary dentition are as follows: i. Spacing of anterior teeth: Spaces existing between the deciduous teeth called as physiologic or developmental spaces are important for normal development of permanent dentition. ii. Primate/anthropoid/simian spaces: These physiologic spaces are present invariably on mesial side of maxillary canines and distal side of mandibular canines. As these spaces are commonly seen in primates, these are known as primate spaces, simian spaces or anthropoid spaces. These spaces help in the placement of the canine cusps of the opposing arch. iii. Shallow overjet and overbite iv. Ovoid arch form v. Almost vertical inclination of anterior teeth vi. Flush terminal plane: The mesiodistal relation between the distal surfaces of the upper and lower second deciduous molars (E) is called the terminal plane. A normal feature of deciduous dentition is a flush terminal plane, where the distal surfaces of the upper and lower second deciduous molars are in the same plane. vii. Deep bite: The deep bite occurs in the initial stages of development and is accentuated by the more upright deciduous incisors compared to their successors. This deep bite is reduced later due to: a. Eruption of deciduous molars b. Attrition of incisors c. Forward movement of the mandible due to growth. MIXED DENTITION PERIOD This period ranges from 6 to 12 years of age. This period can be divided into three phases: 1. First transitional period 2. Intertransitional period 3. Second transitional period. First Transitional Period The distal surface of the second deciduous molar, i.e. (E) guides the first permanent molars into the dental arch. The location and relationship of the first permanent molars depend much on the distal surface relationship between upper and lower second deciduous molars E E The distal surface relationship between the upper and lower second deciduous molars can be of three types: 1. Flush terminal plane (76%) 2. Mesial step terminal plane (14%) 3. Distal step terminal plane (10%). Flush terminal plane (Fig. 4.2) Mandibular first molar is the first permanent tooth to erupt at around 6 years of age. Orthodontics-Part-I-2013.indd 31 D E 6 D Fig. 4.2 Flush terminal plane. The distal surface of the upper and lower second deciduous molars are in one vertical plane. This type of relationship is called flush or vertical terminal plane relationship, which is a normal feature of deciduous dentition. The erupting first permanent molars may also be in a flush or end-on relationship, which shifts to class relation by either of the following: a. Early shift b. Late shift. Early shift: It occurs during early mixed dentition period, where eruptive force of the first permanent molar is sufficient to push the deciduous first and second molars forward to close the primate spaces and establish class I molar relationship. Late shift: It occurs in the late mixed dentition period. In children lacking primate spaces, the erupting permanent first molars drift mesially utilizing the Leeway space, when deciduous second molars exfoliate. Mesial step terminal plane (Fig. 4.3) It is characterized by: 1. Emergence of the first permanent molars 2. Exchange of the deciduous incisors with permanent incisors. Emergence of the first permanent molars E 6 6 6 E E D D Fig. 4.3 Mesial step terminal plane. 12/3/2013 2:49:12 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 32 In this type of relationship, distal surface of mandibular ΂ E E ΂ is more mesial than that of EE maxillary second deciduous molar ΂ ΂. second deciduous molar The permanent molars erupt directly into the Angle’s class I occlusion. If forward growth of mandible Persists Minimal Incisal liability can be overcome by: ❍ utilization of interdental spaces seen in primary dentition, ❍ increase in intercanine width and ❍ change in incisor inclination. Intertransitional Period It is relatively stable and no changes occur during this phase to mixed dentition. The maxillary and mandibular arches consist of sets of deciduous and permanent teeth during this period. Second Transitional Period Leads to Establishes Angle’s class III molar relationship Angle’s class I molar relationship Distal step terminal plane (Fig. 4.4) 6 E D 6 E D Fig. 4.4 Distal step terminal plane. In this type of relationship, the distal surface of E E is more distal to the of E E . Erupting permanent molars assume Angle’s class II occlusion in this relationship. Exchange of incisors The deciduous incisors are replaced by the permanent incisors during first transition period. The mesiodistal width of permanent incisors is larger than deciduous teeth they replace. Incisal liability is the difference between the amount of space needed for accommodation of the incisors and the amount of space available for them to occupy. It was described by Warren Mayne in 1969. Incisal liability is: ❍ 7 mm in maxillary arch and ❍ 5 mm in mandibular arch. Orthodontics-Part-I-2013.indd 32 The replacement of deciduous molars and canines by the premolars and permanent cuspid, respectively, is characteristic of this phase. The Leeway space of Nance is the excess space available after the exchange of the deciduous molars and canines with permanent teeth. It is utilized for mesial drift of mandibular molars to establish class I molar relation. Ugly duckling stage (7–11 years of age): Also known as Broadbent’s phenomenon, it is a transient or self-correcting malocclusion seen in maxillary incisor region, particularly during eruption of permanent canines. During eruption of permanent canines they impinge on roots of lateral incisors displacing them mesially, which in turn results in the transmission of force onto the roots of central incisors, which also get displaced mesially. A resultant distal divergence of crowns of two central incisors causes a midline diastema. This situation has been described by Broadbent as ugly duckling stage, as children tend to look ugly during this phase. Permanent Dentition Period This period extends from shedding of last primary tooth and eruption of all permanent teeth. The frequently seen eruption sequence of the permanent dentition is as follows: 1. Maxillary arch: 6-1-2-4-3-5-7 Or 6-1-2-3-4-5-7 2. Mandibular arch: 6-1-2-3-4-5-7 Or 6-1-2-4-3-5-7 12/3/2013 2:49:12 PM
  • Topic wise Solved Questions of Previous Years 33 SHORT ESSAYS Q. 1. Space of Nance Or Leeway space of Nance Ans. i. The combined mesiodistal width of the permanent canines and premolars is usually less than the deciduous canines and molars, which they replace. This surplus space is called Leeway space of Nance. ii. The Leeway space is greater in the mandibular arch compared to maxillary arch. a. In maxillary arch, it is 1.8 mm (0.9 mm per side of the arch). b. In mandibular arch, it is 3.4 mm (1.7 mm on each size of arch). iii. This space is utilized for establishment of class I molar relation by facilitating mesial drift of mandibular molars. Q. 2. Describe the development of dentition and occlusion. Ans. Development of dentition and occlusion is as follows: Development of dentition and occlusion Predental period (0–6 months from birth) Gum pads: Alveolar arches without teeth, horseshoe shape, pink and firm consistency Deciduous dentition period (6 months–6 years) (complete deciduous teeth formation is 6 months –2½ to 3½ years) Normal features i. Spacing of anterior teeth (physiologic/development spaces) ii. Primate/anthropoid/simian spaces located C↓ ↓C iii. Shallow overjet and overbite iv. Ovoid arch form v. Vertical inclination of anterior teeth vi. Flush terminal plane vii. Deep bite in early stages Orthodontics-Part-I-2013.indd 33 Mixed dentition period (6–12 years) Permanent dentition period (shedding of last primary tooth and eruption of all permanent teeth) 3 phases First transition period Intertransition period Second transition period i. Emergence of Stable and no change i. Characterized by CDE replacement by 345 ii. Leeway space of Nance CDE-345; 1.8 3.4 6 6 6 6 Exchange of A with 1. ii. Location and relation of 6 6 6 6 depends on terminal plane relation of E’s. iii. 3 types of terminal planes a. Flush terminal plane b. Mesial terminal plane c. Distal terminal plane iv. Exchange of incisors incisal stability: Maxillary–7mm Mandibular–5mm Eruption sequence i. Maxilla: 6-1-2-4-3-5-7 ii. Mandible: 6-1-2-3-4-5-7 iii. Ugly duckling stage (8–9 years) eruption of 33 12/3/2013 2:49:12 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 34 Q. 3. Incisal liability Ans. Incisal liability was described by Warren Mayne in 1969. The mesiodistal width of the permanent incisors is larger compared to the primary incisors. For proper alignment of anterior teeth, the erupting permanent incisors require more space. This difference between the amount of space needed for the incisors and the amount available for them is called the incisal liability. A favourable incisal liability exists when the primary dentition is an open dentition, whereas an unfavourable situation exists in closed dentition. The incisal liability is about 7.6 mm in maxillary arch and 6 mm in mandibular arch. Absence of spaces in the primary dentition is an indication that crowding of teeth may occur when the larger permanent teeth erupt. Primate spaces are used in early mesial shift. Q. 5. Transient malocclusions Ans. Transient malocclusions are also known as self-correcting malocclusions or transitional malocclusions. Transient malocclusions are those conditions that look like malocclusion at some particular time. But with normal growth, the condition gets corrected on its own without any treatment. Transient malocclusions observed at various stages of occlusal development are as follows: This space discrepancy is compensated by three mechanisms: i. Increased intercanine width: During the period of permanent incisor eruption, significant amount of increase in intercanine arch width occurs. It is about 3–4 mm. ii. Interdental spacing: Spacing present in primary dentition helps in alignment of incisors. The primate space present in the upper arch mesial to primary canine is also used. iii. Labial eruption of incisor: Deciduous incisors stand upright. The permanent incisors, which replace them, are proclined labially, placing them in a wider arch. A. Stage of predental jaw relation Q. 4. Anthropoid spaces B. Stage of primary dentition Or Physiologic spaces Ans. Generalized spaces present in the deciduous dentition, which plays important role in the normal development of permanent dentition are called as physiologic spaces or developmental spaces. The anteroposterior growth of the jaws is the reason for physiologic spaces. Absence of spaces indicates development of crowding in permanent dentition. Primary dentition in which interdental spaces are present is called open dentition or spaced dentition. For the normal development of the permanent dentition, the presence of spaces in the primary dentition is important. Invariably spacing exists mesial to the maxillary canines and distal to the mandibular canines. These physiologic spaces are called primate spaces, simian spaces or anthropoid spaces, as they are seen commonly in primates. These spaces help in placement of the canine cusps of the opposing arch. Orthodontics-Part-I-2013.indd 34 Existing transient malocclusions Correction mechanism i. Retrognathic mandible Gets corrected with cephalocaudal growth and differential growth of mandible ii. Complete overlap of maxillary Transverse and sagittal growth of gum pad mandibular gum pad iii. Anterior open bite Eruption of primary incisors iv. Infantile swallow With initiation of function at about 18 months of age Type of transient malocclusion present Correction mechanism i. Deep bite Eruption of primary molars ii. Increased overjet Attrition of incisal edges iii. Flush terminal plane More forward growth of the mandible iv. Spacing Early mesial shift v. Edge-to-edge at about 6 Closes with eruption of permanent sucyears of age cessors; shedding of primary incisors and eruption of permanent incisors C. Mixed dentition Transient malocclusion Reason for correction i. Deep bite Physiologic bite raisers at 6–12 years with the eruption of 1st and 2nd permanent molars. The overlying gingival pad of tissue will act as bite raiser ii. Ugly duckling stage Eruption of maxillary canine iii. Lower anterior crowding Increase in intercanine width iv. End-on molar relationship Late mesial shift v. Flush terminal plane Both late mesial shift and differential jaw growth 12/3/2013 2:49:12 PM
  • Topic wise Solved Questions of Previous Years 35 Q. 6. Andrews’ keys to normal occlusion Or Write about Roth’s keys of occlusion. Ans. There are two keys of occlusion: i. Andrews’ keys of static occlusion and ii. Roth’s keys of functional occlusion. Andrews’ keys of static occlusion Key 1: Molar relation Mesiobuccal cusp of maxillary first molar rests in the mesiobuccal groove of mandibular first molar. Distal surface of the distobuccal cusp of maxillary first molar should occlude with mesial surface of the mesiobuccal cusp of mandibular second molar. Mesiolingual cusp of the maxillary first molar should occlude in the central fossa of mandibular first molar. Key 2: Crown angulations (tip) The gingival portion of the long axis of each crown should be distal to the incisal portion, this is known as crown angulation. Measured by the inclination of long axis of the crown to a line perpendicular to the occlusal plane. Key 3: Crown inclination (torque) The buccolingual inclination of the long axis of the crown and not the long axis of the entire tooth is known as crown inclination. Negative crown inclination or lingual crown inclination occurs in the maxillary and mandibular posteriors, whereas positive or labial inclination is seen in maxillary incisors. Key 2: Maximum and stable cusp to fossa contacts throughout the buccal segments. Key 3: Disclusion of the posterior teeth in mandibular protrusion by even contacts on the incisors. Key 4: Lateral movements of the mandible are guided by the working side canines, with disclusion of all the other teeth on both working and non-working sides. Q. 7. Ugly duckling stage Ans. Ugly duckling stage is also known as Broadbent’s phenomena or physiologic median diastema. Ugly duckling stage is a transient form of malocclusion in which midline diastema is present between the maxillary central incisors. It is commonly seen between 7 and 11 years of age. During the eruption stages of canine it will be impinging on the roots of lateral incisors and resulting pressure causes the lateral incisor to erupt into the oral cavity with divergence of crown distally. Even after the lateral incisor fully erupts, this pressure effect from the erupting canine persists and is transmitted to the central incisors also, which results in the divergence of crowns and convergence of roots towards midline. This bilateral effect causes a temporary midline diastema. This temporary spacing that occurs between the central incisors and sometimes between central and lateral incisors gets closed automatically, as the canine comes into occlusion. This stage is called ugly duckling stage because it represents a metamorphosis from an unaesthetic phase to an aesthetic phase. Key 4: Rotation The resulting angle between a line perpendicular to the occlusal plane and one tangent to the middle of the labial or buccal clinical crown is known as rotation. Absence of rotation. Arch should be devoid of any rotated tooth. A rotated molar occupies more mesiodistal space, creating a situation unreceptive to normal occlusion while a rotated incisor occupies less space. Clinical significance As a guideline, spontaneous closure of maxillary midline diastema up to 2 mm is more likely, while total closure of a median diastema greater than 2 mm is unlikely. During ugly duckling stage any attempt to close the median diastema will be hazardous. Apex of the lateral incisors will be damaged and canine may be deflected from its normal path of eruption. Key 5: Interproximal contact Proximal contacts should be tight and no spacing should be present. Q. 8. Terminal planes Key 6: Curve of Spee Deep curve of Spee results in crowding. Flat curve of Spee is most receptive for normal occlusion. Reverse curve of Spee results in spacing. Roth’s keys of functional occlusion Key 1: Coincidence of intercuspal position (ICP) and retruded contact position (RCP). Orthodontics-Part-I-2013.indd 35 Or Flush terminal plane Ans. The distal surface relationship between the upper and lower second deciduous molars is known as terminal plane relationship. It can be of three types: 1. Flush terminal plane (76%) 2. Mesial step terminal plane (14%) 12/3/2013 2:49:12 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 36 3. Distal step terminal plane (10%). Flush terminal plane (See Fig. 4.2) The distal surface of the upper and lower second deciduous molars are in one vertical plane. This type of relationship is called flush or vertical terminal plane relationship, which is a normal feature of deciduous dentition. The erupting first permanent molars may also be in a flush or end-on relationship, which shifts to class relation by either of the following: i. Early shift ii. Late shift Early shift: It occurs during early mixed dentition period, where eruptive force of the first permanent molar is sufficient to push the deciduous first and second molars forward to close the primate spaces and establish class I molar relationship. Late shift: It occurs in the late mixed dentition period. In children lacking primate spaces, the erupting permanent first molars drift mesially, utilizing the Leeway space when deciduous second molars exfoliate. Mesial step terminal plane (See Fig. 4.3) In this type of relationship, distal surface of mandibular second deciduous molar (E E) is more mesial than that of maxillary second deciduous molar (E E).The permanent molars erupt directly into the Angle’s class I occlusion. If forward growth of mandible is minimal, it establishes Angle’s class I molar relationship, whereas if forward growth of mandible persists it leads to Angle’s class III molar relationship. Distal step terminal plane (See Fig. 4.4) In this type of relationship, the distal surface of E E is more distal to the of E E . Erupting permanent molars assume Angle’s class II occlusion in this type of relationship. Q. 9. Curve of Spee Ans. Curve of Spee refers to the anteroposterior curvature of the occlusal surfaces beginning at the tip of the lower cuspid and following the cusp tips of the bicuspids and molars continuing as an arc through the condyle. If the curve is extended, it would form a circle of about 4 inch diameter. The curve results from variations in axial alignment of the lower teeth. The long axis of each lower tooth is aligned nearly parallel to its individual arc of closure around the condylar axis. This requires a gradual progressive Orthodontics-Part-I-2013.indd 36 increased mesial tilting of teeth towards molars, which creates the curve of Spee. Deep curve of Spee results in crowding. Flat curve of Spee is most receptive for normal occlusion. Reverse curve of Spee results in spacing. Q. 10. Gum pads Ans. The neonate is without teeth for about 6 months of life. The alveolar arches of an infant at this time period are known as gum pads. The features of gum pads are as follows: i. These are pink in colour, firm in consistency and covered by dense layer of fibrous periosteum. ii. They are horseshoe shaped and develop in two parts: a. Labiobuccal portion b. Lingual portion. Dental groove (See Fig. 4.1) These two portions are separated by a groove called the dental groove. Transverse grooves The gum pads are divided into 10 segments by transverse grooves. Each segment consists of one developing deciduous tooth sac. Lateral sulcus The transverse groove between the canine and first deciduous molar segment is called the lateral sulcus. The lateral sulcus of mandibular arch is normally more distal to that of maxillary arch. The lateral sulci are useful in judging the interarch relationship of maxilla and mandible at every early stage. Upper and lower gum pads are almost similar to each other. Relationship of gum pads When upper and lower gum pads are approximated, there is a complete overjet all around, as the upper gum pad is wider as well as longer than lower gum pad. Mandibular lateral sulci are posterior to maxillary ones. Class II pattern is exhibited as maxillary gum pad being more prominent. Anterior open bite: This infantile open bite is considered normal. Contact occurs between the upper and lower gum pads in first molar region and a space exists between them anteriorly known as infantile open bite, which helps in sucking. 12/3/2013 2:49:12 PM
  • Topic wise Solved Questions of Previous Years 37 SHORT NOTES Q. 1. Gum pads Ans. The alveolar arches at the time of birth are called gum pads and are firm and pink in colour. Maxillary gum pads develop in two parts, namely, labiobuccal and lingual. These are demarcated by the dental groove. Labiobuccal part grows fast and is divided into 10 segments by transverse grooves, which correspond to the deciduous tooth sac. The groove between the canine and deciduous first molar is called lateral sulcus. Gingival groove demarcates the palate from gum pads. Lower gum pads are V shaped and similar to maxillary gum pads; but the segments are less defined when compared to maxillary gum pad. Relationship of gum pads is arbitrary. They do not have definite relationship. When upper and lower gum pads are approximated, there is a complete overjet all around. Class II pattern is exhibited with anterior open bite, this infantile open bite is considered normal. Q. 2. Primate spaces Ans. Generalized spaces present in the deciduous dentition, which plays important role in the normal development of permanent dentition are called as primate spaces, physiologic spaces or developmental spaces. The anteroposterior growth of the jaws is the reason for physiologic spaces. Absence of spaces indicates development of crowding in permanent dentition. Invariable spacing exists mesial to the maxillary canines and distal to the mandibular canines. These physiologic spaces are called primate spaces, simian spaces or anthropoid spaces, as they are seen commonly in primates. These spaces help in placement of the canine cusps of the opposing arch. Primate spaces are used in early mesial shift. Q. 3. Incisor liability Ans. Incisal liability was described by Warren Mayne in 1969. The mesiodistal width of the permanent incisors is larger compared to the primary incisors. Orthodontics-Part-I-2013.indd 37 This difference between the amount of space needed for the incisors and the amount available for them is called the incisal liability. A favourable incisal liability exists when the primary dentition is an open dentition, whereas an unfavourable situation exists in closed dentition. The incisal liability is about 7.6 mm in maxillary arch and 6 mm in mandibular arch. Q. 4. Ugly duckling stage Ans. Ugly duckling stage is also known as Broadbent’s phenomena or physiologic median diastema. Ugly duckling stage is a transient form of malocclusion in which midline diastema is present between the maxillary central incisors. It is commonly seen between 7 and 11 years of age. During the eruption stages of canine, it will be impinging on the roots of lateral incisors, and resulting pressure causes the lateral incisor to erupt into the oral cavity with divergence of crown distally. This temporary spacing that occurs between the central incisors and sometime between central and lateral incisors gets closed automatically as the canine comes into occlusion. This stage is called ugly duckling stage because it represents a metamorphosis from an unaesthetic phase to an aesthetic phase. Q. 5. Leeway space Or Leeway space of Nance Ans. The combined mesiodistal width of the permanent canines and premolars is usually less than the deciduous canines and molars that they replace. This surplus space is called leeway space of Nance. The leeway space is greater in the mandibular arch compared to maxillary arch. ❍ In maxillary arch, it is 1.8 mm (0.9 mm per side of the arch). ❍ In mandibular arch, it is 3.4 mm (1.7 mm on each size of arch). 12/3/2013 2:49:12 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 38 This space is utilized for establishment of class I molar relation by facilitating mesial drift of mandibular molars. Q. 6. Distal flush terminal plane Q. 9. Sequence of eruption of permanent teeth Ans. Distal flush terminal plane (See Fig. 4.4) The period of permanent dentition extends from shedding of last primary tooth and eruption of all permanent teeth. The frequently seen eruption sequence of the permanent dentition is as follows: Maxillary arch: 6-1-2-4-3-5-7 Or 6-1-2-3-4-5-7 Mandibular arch: 6-1-2-3-4-5-7 Or 6-1-2-4-3-5-7 In this type of relationship, the distal surface of E E is more Q. 10. Transient malocclusion Ans. The distal surface relationship between the upper and lower second deciduous molars is known as terminal plane relationship. It can be of three types: i. Flush terminal plane (76%) ii. Mesial step terminal plane (14%) iii. Distal step terminal plane (10%). distal to that the E E . Or Erupting permanent molars assume Angle’s class II occlusion in this type of relationship. Transitional period Q. 7. Flush terminal plane Enumerate few self-correcting malocclusions. Ans. Ans. Flush terminal plane (See Fig. 4.2) The distal surface of the upper and lower second deciduous molars are in one vertical plane. This type of relationship is called flush or vertical terminal plane relationship, which is a normal feature of deciduous dentition. The erupting first permanent molars may also be in a flush or end-on relationship, which shifts to class relation by either early shift or late shift. Q. 8. Theories of eruption Ans. The exact mechanism by which the tooth erupts is still unclear. Cross-linking of the maturational fibres of periodontal ligament provides the force for eruption. This seems to be the contemporary view. The various theories of eruption are as follows: i. Pulp theory ii. Vascular theory iii. Root elongation theory iv. Alveolar bone growth theory v. Genetic theory vi. Follicular theory vii. Hammock ligament theory. Orthodontics-Part-I-2013.indd 38 Or Transient malocclusions are also known as self-correcting malocclusions or transitional malocclusions. Transient malocclusions are the conditions that will look like malocclusion at some particular time. But with normal growth, the condition gets corrected on its own without any treatment. Transient malocclusions observed at various stages of occlusal development are as follows: 1. Stage of predental jaw relation a. Retrognathic mandible gets corrected with cephalocaudal growth and differential growth of mandible. b. Anterior open bite corrects itself with eruption of primary incisors. 2. Stage of primary dentition a. Deep bite gets corrected with the eruption of primary molars b. Spacing gets closed with early mesial shift 3. Mixed dentition a. Ugly duckling stage corrects itself with eruption of maxillary canine. b. Lower anterior crowding gets corrected with increase in intercanine width. Q. 11. Andrews’ keys to normal occlusion 12/3/2013 2:49:12 PM
  • Topic wise Solved Questions of Previous Years 39 Or Enumerate Andrews’ six keys to normal occlusion. Ans. Andrews’ keys of static occlusion are as follows: Key 1: Molar relation superior and retruded position in glenoid fossa with the articular disc properly interposed. Centric relation is also called ligamentous position or terminal hinge position. At centric relation position both the condyles are simultaneously seated most superiorly and far back in unstrained position in the respective glenoid fossa. Mesiobuccal cusp of maxillary first molar rests in the mesiobuccal groove of mandibular first molar. Q. 14. Roth’s keys of functional occlusion Key 2: Crown angulations (tip) Ans. The gingival portion of the long axis of each crown should be distal to the incisal portion, this is known as crown angulation. Key 3: Crown inclination (torque) The buccolingual inclination of the long axis of the crown and not the long axis of the entire tooth is known as crown inclination. Key 4: Rotation The resulting angle between a line perpendicular to the occlusal plane and one tangent to the middle of the labial or buccal clinical crown is known as rotation. Key 5: Interproximal contact Proximal contacts should be tight and no spacing should be present. Key 6: Curve of Spee It refers to the anteroposterior curvature of the occlusal surfaces beginning at the tip of the lower cuspid and following the cusp tips of the bicuspids, and molars continuing as an arc through the condyle. A flat curve of Spee is most receptive for normal occlusion. Q. 12. Enumerate the stages of eruption of normal occlusal development. Ans. Occlusal development can be divided into the following stages: i. Predental period: Birth to 6 months ii. Deciduous dentition period: 6 2½–3½ years iii. Mixed dentition period: 6–12 years iv. Permanent dentition period: Starts after shedding of last primary tooth. Q. 13. Centric relation Ans. Centric relation is the relation of the mandible to the maxilla when the mandibular condyles are in the most Orthodontics-Part-I-2013.indd 39 Roth’s keys of functional occlusion are: Key 1: Coincidence of intercuspal position (ICP) and retruded contact position (RCP). Key 2: Maximum and stable cusp to fossa contacts throughout the buccal segments. Key 3: Disclusion of the posterior teeth in mandibular protrusion by even contacts on the incisors. Key 4: Lateral movements of the mandible are guided by the working side canines, with disclusion of all the other teeth on both working and non-working sides. Q. 15. Premature loss of deciduous teeth Ans. Premature or early loss of deciduous teeth causes the following: Migration of adjacent teeth into the space that prevents eruption of successor. Premature loss of deciduous teeth leads to development of malocclusion. Loss of deciduous second molar can cause marked forward shift of the permanent first molar, thereby blocking eruption of the second premolar, which gets impacted or deflected to abnormal position. Q. 16. Enumerate the stages of tooth development. Ans. The development of tooth was divided into 10 stages by Nolla as follows: i. Stage 1: Presence of crypt ii. Stage 2: Initial calcification iii. Stage 3: One-third of crown completion iv. Stage 4: Two-thirds of crown completion v. Stage 5: Crown almost completed vi. Stage 6: Crown completed vii. Stage 7: One-third of root completed viii. Stage 8: Two-thirds of crown completion ix. Stage 9: Root almost completed with open apex x. Stage 10: Apical end of the root completed. 12/3/2013 2:49:12 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 40 Topic 5 FUNCTIONAL DEVELOPMENT LONG ESSAYS Q. 1. Discuss in detail various functions of stomatognathic system. Ans. Salzmann defined stomatognathics as an approach to the practice of orthodontics that takes into consideration the interdependence of form and function of the teeth, jaw relationship, temporomandibular articulation, craniofacial conformation and dental occlusion. The various functions of stomatognathic system are as follows: 1. Mastication 2. Deglutition 3. Respiration 4. Speech. 1. Mastication Mastication can be grouped as: a. Infant feeding (before teeth eruption) b. Mature or adult mastication (after teeth eruption). a. Infant feeding Infants consume food by suckling—an automatic reflex. In infants, suckling and swallowing proceed together as suckle-swallow, which is characterized by caving in of the cheeks, bobbing of the hyoid bone, extended head with anterior mandibular thrust and elongated tongue, with lips pursed around the nipple. Moyers lists the features of the infantile swallow as: Infantile swallow is guided by the lips and tongue. Jaws are apart with the tongue placed between the gum pads. Mandible is positioned by muscles of the facial expression. The various types of infant feeding are as follows: i. Breastfeeding: Milk is directed to the pharynx by the peristaltic movement of the tongue. ii. Bottle feeding: Milk is expelled into the mouth. iii. Spoon feeding: Lips are sealed around the edge of spoon to draw food into the mouth. Orthodontics-Part-I-2013.indd 40 Tongue passes the bolus of food to swallowing between gum pads and erupting teeth. Mature swallowing patterns are observed usually by 18 months of age. b. Adult mastication Mastication is defined as the reduction of food in size, changing in consistency, mixing it with saliva and forming into a bolus suitable for swallowing. The features of adult swallow are: Teeth are together. Mandible is stabilized by muscles of mastication. The six stages of mastication as outlined by Murphy are as follows: i. Preparatory phase ii. Food contact phase iii. Crushing phase iv. Tooth contact phase v. Grinding phase vi. Centric occlusion. i. Preparatory phase The ingested food is positioned by the tongue. Mandible moves towards the chewing side. ii. Food contact phase: After food is ingested, there is a momentary pause in chewing as the sensory receptors study the consistency of the food. iii. Crushing phase: Crushing of the ingested food starts with high velocity and later slows down. iv. Tooth contact phase: After 4–5 strokes of crushing phase, tooth contact happens accompanied by change in direction of chewing. v. Grinding phase During this phase, unilateral chewing of food particles takes place. During grinding vigorous contact of the maxillary and mandibular molars occurs. vi. Centric occlusion Movement of the teeth comes to a halt. After this stage, preparatory stage of the next stroke of mastication begins. 12/3/2013 2:49:12 PM
  • Topic wise Solved Questions of Previous Years 41 2. Deglutition Stages of deglutition Fletcher divided the deglutition pattern into four stages: i. Preparatory phase ii. Oral phase iii. Pharyngeal phase iv. Oesophageal phase. i. Preparatory phase This phase starts as soon as food is ingested. The liquid or crushed food is placed in swallow preparatory position and mouth is sealed by lips or tongue. ii. Oral phase Soft palate moves upward, and tongue drops downward and backward. Larynx and hyoid move upward. Muscles of mastication play an active role in stabilization. A smooth path is created for the bolus, solid food is pushed by the tongue and liquid food just flows down. iii. Pharyngeal phase It begins as the bolus of food passes through the fauces. Nasopharynx is closed, and tongue and hyoid bone move forwards. iv. Oesophageal phase: Food passes through the cricopharyngeal sphincter through oesophagus to the stomach. 3. Speech and Malocclusion Speech is a learned behaviour. Lips, tongue and velopharyngeal structures modify the outgoing breathing stream to produce different variations in speech. Bilabial sounds are the first sound to be developed. Example of various sounds: Bilabial (lips) → ‘p’, ‘b’ Labiodental→ ‘f ’, ‘v’ Linguodental→ ‘th’ Lingua-alveolar →‘t’, ‘d’, s Linguopalatal → ‘ch’, ‘sh’. SHORT ESSAYS Q. 1. Trajectories of force a. Maxillary trajectories Ans. Maxilla provides maximum strength with minimum material because of the following trajectories. They are as follows: The trajectorial theory states that the lines of orientation of the bony trabeculae follow the pathways of maximal pressure and tension. Benninghoff did extensive study on dried craniofacial bones and said that stress trajectories or lines of orientation of the bony trabeculae involve not only the cancellous bone but also the compact bone. These trajectories or functional lines are otherwise called Benninghoff lines. The stress trajectories respond to the demands of functional forces collectively as a unit and not as a single bone. Accordingly, the head is made up of only two functional units: 1. Craniofacial unit 2. Mandible. 1. Craniofacial Unit The trajectories extend in a fan-like fashion from the midpalatal suture across the alveolar bone through the maxilla and end at the base of the skull. The bones of the face are united with the cranial bones by these fan-like trajectories, which continue across the facial bones and do not stop at the suture. Orthodontics-Part-I-2013.indd 41 Frontonasal/canine pillar Vertical pillars Maxillary trajectories Malar zygomatic pillar Pterygoid pillar Horizontal reinforcing members: Trajectories from hard palate, orbital walls, zygomatic arches, palatal bones and lesser wing of sphenoid i. Vertical pillars i. Frontonasal vertical pillar/buttress: This pillar or buttress runs vertically along piriform aperture and crest of the nasal bones and ends in the frontal bone, transmitting pressures from the incisors, canines and first premolar. ii. Malar zygomatic vertical pillar/buttress In the zygomatic area, it splits into three parts—one passes through the zygomatic arch, other passes along lateral border of orbit and the last one passes along lower border of orbit; finally all three parts end at the base of the skull. It transmits stress from the posterior teeth and also receives force of the masseter muscles. 12/3/2013 2:49:12 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 42 iii. Pterygoid vertical pillar/buttress: It runs vertically from the conchae of nasal cavity and posterior teeth ending in the middle portion of the base of the skull. ii. Horizontal reinforcing members Supraorbital rim acts as a receptor of forces from canine and zygomatic pillar. Other reinforcing members are infraorbital, zygomatic buttress, hard palate, walls of orbit and lesser wings of sphenoid. 2. Trajectories of Mandible Muscles of mastication play an active role in stabilization. A smooth path is created for the bolus, solid food is pushed by the tongue and liquid food just flows down. iii. Pharyngeal phase It begins as the bolus of food passes through the fauces. Nasopharynx is closed, and tongue and hyoid bone move forward. iv. Oesophageal phase Food passes through the cricopharyngeal sphincter through oesophagus to the stomach. Mandible is made of major and minor trajectories. i. Major trajectories Trabecular columns originate from beneath the teeth in the alveolar process and join together into a common stress pillar or trajectory system. Mandibular canal and nerve are protected by this concentration of trabeculae. High resistance to bending forces is provided by the thick cortical layer of trabeculae present along the lower border of the mandible. ii. Minor trajectories These minor accessory stress trajectories are due to the effect of muscle attachments. For example, trajectories are seen at the symphysis, gonial angle, and one trabecular pattern is seen running downwards from the coronoid process into the ramus and body of the mandible. Q. 2. Deglutition Ans. Deglutition starts at 32 weeks in the utero. Mature swallowing patterns are observed usually by 18 months of age. Fletcher divided the deglutition pattern into four stages: i. Preparatory phase ii. Oral phase iii. Pharyngeal phase iv. Oesophageal phase. i. Preparatory phase This phase starts as soon as food is ingested. The liquid or crushed food is placed in swallow preparatory position and mouth is sealed by lips or tongue. ii. Oral phase Soft palate moves upward and tongue drops downward and backward. Larynx and hyoid move upward. Orthodontics-Part-I-2013.indd 42 Q. 3. Buccinator mechanism Ans. Teeth and supporting structures of the jaw are under the control of the adjacent muscles. The balance between the muscles is responsible for the integrity of the dental arches and the relation of teeth to the arches. Buccinator mechanism is a phenomenon where a continuous band of muscles encircle the dentoalveolar region from the buccal aspect, and is firmly anchored at the pharyngeal tubercle of the occipital bone. It starts with the decussating fibres of the orbicularis oris joining the right and left fibres of the lip, which constitute the anterior component of the buccinator mechanism. It runs laterally and posteriorly around the corner of the mouth, joining other fibres of the buccinator muscle, which gets inserted into the pterygomandibular raphe. It mingles with the fibres of superior constrictor muscle, and runs posteriorly and medially to get fixed to the pharyngeal tubercle. All these 13 muscles with elasticity and contractility act like a rubber band tightly encircling the bone system, i.e. mandible. Tongue acts opposing the buccinator mechanism from within, exerting an outward force. The dentition is in a constant state of dynamic equilibrium. There is a balance of forces between muscles that are believed to influence the position and stability of the dentoalveolar complex. Clinical significance Malocclusion is caused due to any imbalance in buccinator mechanism. Due to certain deleterious oral habits like thumb sucking, tongue thrusting, etc., the equilibrium between buccinator mechanism and tongue is lost, causing constricted maxillary arch, increased proclination and open bite, etc. 12/3/2013 2:49:13 PM
  • Topic wise Solved Questions of Previous Years 43 SHORT NOTES Q. 1. Trajectories of force in mandible Q. 4. Buccinator mechanism Ans. Ans. Mandible is made of major and minor trajectories. Trabecular columns originate from beneath the teeth in the alveolar process and join together into a common stress pillar or major trajectory system. Mandibular canal and nerve are protected by this concentration of trabeculae. The minor accessory stress trajectories are due to the effect of muscle attachments. Example: Trajectories seen at the symphysis, gonial angle, and one trabecular pattern is seen running downwards from the coronoid process into the ramus and body of the mandible. Q. 2. Wolff’s law of transformation of bone Or Discuss about Wolff’s law of transformations of bone. Buccinator mechanism is a phenomenon where a continuous band of muscles encircle the dentoalveolar region from the buccal aspect and is firmly anchored at the pharyngeal tubercle of the occipital bone. It starts with the decussating fibres of the orbicularis oris joining the right and left fibres of the lip, which constitute the anterior component of the buccinator mechanism. It then runs laterally and posteriorly around the corner of the mouth, joining other fibres of the buccinator muscle which gets inserted into the pterygomandibular raphe. It mingles with the fibres of superior constrictor muscle, and runs posteriorly and medially to get fixed to the pharyngeal tubercle. All these 13 muscles with elasticity and contractility act like a rubber band tightly encircling the bone system, i.e. mandible. Tongue acts opposing the buccinator mechanism from within, exerting an outward force. Ans. Wolff ’s law of transformation of bone In the year 1870, Julius Wolff attributed the arrangement of trabecular pattern of bone to the functional forces. A change in the direction and magnitude of force could produce a marked change in the internal architecture and external form of the bone. This is called Wolff ’s law of transformation of bone. Increase in function leads to increase in density of bone while lack of function leads to decrease in trabecular pattern. Simply stated stresses of tension or pressure on bones stimulate changes within the bone. Q. 3. Infantile swallow Ans. Infants consume food by suckling. In Infants, suckling and swallowing proceed together as suckle-swallow, which is characterized by caving in of the cheeks, bobbing of the hyoid bone, extended head with anterior mandibular thrust and elongated tongue, with lips pursed around the nipple. Moyers lists the features of the infantile swallow as: Infantile swallow is guided by the lips and tongue. Jaws are apart with the tongue placed between the gum pads. Mandible is positioned by muscles of the facial expression. Orthodontics-Part-I-2013.indd 43 Q. 5. Trajectories of facial skeleton Ans. Benninghoff stated that stress trajectories or lines of orientation of the bony trabeculae involve not only the cancellous bone but also the compact bone. These trajectories or functional lines are otherwise called Benninghoff lines. Maxilla provides maximum strength because of the following trajectories: Frontonasal/canine pillar Vertical pillars Malar zygomatic pillar Pterygoid pillar Maxillary trajectories Horizontal reinforcing members: Trajectories from hard palate, orbital walls, zygomatic arches, palatal bones and lesser wing of sphenoid Major trajectories Mandibular trajectories Minor trajectories Major trabecular columns originate from beneath the teeth in the alveolar process and join together into a common stress pillar or trajectory system. 12/3/2013 2:49:13 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 44 The minor accessory stress trajectories are due to the effect of muscle attachments, e.g. trajectories seen at the symphysis, gonial angle. Q. 6. Pterygoid response Ans. Pterygoid vertical pillar/buttress runs vertically from the conchae of nasal cavity and posterior teeth, ending in the middle portion of the base of the skull. Topic 6 It is one of the vertical pillars of maxillary trajectories. The trajectorial theory states that the lines of orientation of the bony trabeculae follow the pathways of maximal pressure and tension. These trajectories or functional lines are otherwise called Benninghoff lines. The stress trajectories respond to the demands of functional forces collectively as a unit and not as a single bone. OCCLUSION: BASIC CONCEPTS LONG ESSAYS Q.1. What are the six keys of normal occlusion? State how Ackerman–Proffit’s system is an improvement over Angle’s classification. Ans. Andrews in 1970 put forward the keys to normal occlusion. Andrews’ six keys to normal occlusion are as follows: i. Molar interarch relationship ii. Mesiodistal crown angulation iii. Labiolingual crown inclination iv. Absence of rotation v. Tight contacts vi. Curve of Spee Mesiobuccal cusp of 6 6 should occlude in the groove between the mesial and mesiobuccal cusp of 6 6. Mesiolingual cusp of 6 6 should occlude in central fossa of 6 6 . Crown of 6 6 must be angulated so that distal marginal ridge occludes with mesial marginal ridge of 7 7. ii. Mesiodistal crown angulation i. Molar interarch relationship G D M Fig. 6.2 Mesiodistal crown angulation. For occlusion to be considered normal of the gingival part of the long axis of the crown must be distal to the occlusal part of the line. Different teeth exhibit different crown angulation. Fig. 6.1 Molar interach relationship. Orthodontics-Part-I-2013.indd 44 iii. Labiolingual crown inclination The crown inclination is determined from a mesial or distal view. 12/3/2013 2:49:13 PM
  • Topic wise Solved Questions of Previous Years 45 If gingival area of the crown is more lingually placed than the occlusal area, it is called positive crown inclination. If gingival area of crown is more labially or buccally placed than the occlusal area, it is called negative crown inclination. iv. Absence of rotation Normal occlusion is characterized by absence of any rotation. Rotated posterior teeth occupy more space in the arch. Rotated anterior incisors occupy less space in the arch. v. Tight contacts: To consider an occlusion as normal, there should be tight contact between adjacent teeth. vi. Curve of Spee: A normal occlusion plane according to Andrews should be flat, with the curve of Spee not exceeding 1.5 mm. Normal occlusion Angle’s concept of normal occlusion is based on: (i) key of occlusion and (ii) line of occlusion. i. Key of occlusion Angle considered maxillary first molar as and this is related to key ridge position the key of occlusion, as it is most constant in its position and this is related to key ridge position. According to Angle the mesiobuccal cusp of upper first molar rests in the mesiobuccal groove of mandibular first molar in normal occlusion, i.e. class I molar relation. ii. Line of occlusion There are two lines of occlusion, namely, maxillary and mandibular. The maxillary line of occlusion is a smooth curve that passes through central fossa of upper molars and along the cingulum of upper canines and incisors. Mandibular line of occlusion runs along the buccal cusps of posterior and incisal edges of anteriors. According to Angle, in normal occlusion full complement of teeth should be present. Lines of occlusion are intact in both maxillary and mandibular arches, and molars in class I relation. SHORT ESSAYS Q. 1. What are the forces of occlusion? Ans. The forces of occlusion are of three types: i. Forward or anterior force ii. Distal and lingual force iii. Anterior resultant force. i. Forward or anterior force Forward force is also called anterior component force. It comes into effect after the eruption of first permanent molar into occlusion. This force is produced due to relationship of long axis of teeth to the occlusal surfaces and action of muscles like buccinator and masseter on the teeth. ii. Distal and lingual force Distal and lingual forces are produced by circumoral muscles and buccinators. These forces act on incisors and help to keep canines in place. iii. Anterior resultant force This force is the anterior resultant of the two forces, which act in the opposite way. In spite of these forces, teeth have inherent disposition to drift mesially. Q. 2. Describe six keys to normal occlusion. Ans. Orthodontics-Part-I-2013.indd 45 The six keys to normal occlusion were proposed by Lawrence F Andrews in 1970. The six keys to normal occlusion are as follows: i. Molar interarch relationship ii. Mesiodistal crown angulation iii. Labiolingual crown inclination iv. Absence of rotation v. Tight contacts vi. Curve of Spee. i. Molar interarch relationship: Mesiobuccal cusp of 6 6 should occlude in the groove between the mesial and ii. iii. iv. v. vi. mesiobuccal cusp of 6 6. Mesiodistal crown angulation: Different teeth exhibit different crown angulations. For occlusion to be considered normal the gingival part of the long axis of the crown must be distal to the occlusal part of the crown. Labiolingual crown inclination: The crown inclination is determined from a mesial or distal view. The teeth exhibit either positive crown inclination or negative crown inclination. Absence of rotation: Normal occlusion is characterized by the absence of any rotation. Tight contacts: To consider an occlusion as normal there should be tight contact between adjacent teeth. Curve of Spee: A normal occlusion plane according to Andrews should be flat, with the curve of Spee not exceeding 1.5 mm. 12/3/2013 2:49:13 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 46 Andrews considered the presence of these features essential to achieve normal occlusion. Q. 3. Roth’s keys of functional occlusion Ans. Roth’s keys of functional occlusion are: Key 1: Coincidence of intercuspal position (ICP) and retruded contact position (RCP). Key 2: Maximum and stable cusp to fossa contacts throughout the buccal segments. Key 3: Disclusion of the posterior teeth in mandibular protrusion by even contacts on the incisors. Key 4: Lateral movements of the mandible are guided by the working side canines, with disocclusion of all the other teeth on both working and non-working sides. Q. 4. Occlusal plane Ans. Fig. 6.3 Curve of Spee. Curve of Wilson (Fig. 6.4) This is a curve that contacts the buccal and lingual cusp tips of the mandibular buccal teeth. The curve of Wilson is mediolateral on each side of the arch. It results from inward inclination of the lower posterior teeth. It helps in two ways. Teeth are aligned parallel to the direction of medial pterygoid for opposing resistance to mastication and elevated buccal cusps prevent the food from going palatally. Imaginary occlusal planes and curves Curve of Spee A–P curvature of the occlusal surfaces beginning at the tip of lower cuspid and following the cusp tips of the tricuspids and molars continuing as an arch through the condyle. If the curve is extended, it would follow a circle of about 4 inch diameter. Fig. 6.4 Curve of Wilson. SHORT NOTES Q. 1. Curve of Spee Q. 2. Overjet and overbite Ans. Curve of Spee (Fig. 6.3) refers to anteroposterior curvature of the occlusal surfaces beginning at the tip of the lower cuspid and following the cusp tips of the bicuspids and molars continuing as an arc through the condyle. If the curve is extended, it would form a circle of about 4 inch diameter. The curvature results from variations in axial alignment of the lower teeth. The long axis of each lower tooth is aligned nearly by parallel to its individual arc of closure around the condylar axis. This requires a gradual, progressive, increased mesial tilting of teeth towards molars, which creates the curve of Spee. Orthodontics-Part-I-2013.indd 46 Or Overjet Ans. Overjet Overjet is seen more initially in primary dentition. The average overjet in primary dentition is 1–2 mm. With the movement of the whole dental arch anteriorly, overjet decreases. Overbite In normal overbite, the upper incisors slightly overlap the lower incisors. It is usually expressed in millimetres. Normal value of overbite: 1–3 mm. 12/3/2013 2:49:13 PM
  • Topic wise Solved Questions of Previous Years 47 The overbite is described as percentage of the mandibular incisor crown length overlapped by maxillary central incisors. About 5–20% overlapping of the mandibular incisors are considered normal. Q. 3. Normal occlusion concept Or Features of normal occlusion Ans. Angle’s concept of normal occlusion is based on key of occlusion and line of occlusion. Key of occlusion Angle considered maxillary first molar as the key of occlusion. According to Angle, the mesiobuccal cusp of upper first molar rests in the mesiobuccal groove of mandibular first molar in normal occlusion, i.e. class I molar relation. There are two lines of occlusion, namely, maxillary and mandibular. The maxillary line of occlusion is a smooth curve that passes through central fossa of upper molars and along the cingulum of upper canines and incisors. Mandibular line of occlusion runs along the buccal cusps of posteriors and incisal edges of anteriors. According to Angle, in normal occlusion, full complement of teeth should be present. Lines of occlusion are intact in both maxillary and mandibular arches and molars in class I relation. 7 Ans. Centric relation Centric relation is also called ligamentous position or terminal hinge position. It is the relation of the mandible to the maxilla when the mandibular condyles are in the most superior and retruded position in their glenoid fossa with the articular disc properly interposed. Centric occlusion Centric occlusion is also called intercuspal position or convenience occlusion. Centric occlusion is the position of the mandibular condyle when the teeth are in maximum intercuspation. Q. 5. Enlist Andrews’ six keys to normal occlusion. Or Describe six keys to normal occlusion. Ans. Line of occlusion Topic Q. 4. Centric relation and centric occlusion The six keys to normal occlusion were proposed by Lawrence F Andrews in 1970. He considered the presence of these features essential to achieve normal occlusion. The six keys to normal occlusion are as follows: i. Molar interarch relationship ii. Mesiodistal crown angulation iii. Labiolingual crown inclination iv. Absence of rotation v. Tight contacts vi. Curve of Spee. CLASSIFICATION OF MALOCCLUSION LONG ESSAYS Q. 1. What is classification and what are its advantages? Discuss different methods of classifications on malocclusion. Or Name the different methods of classification of malocclusion. Write about Simon’s classification of malocclusion. Orthodontics-Part-I-2013.indd 47 Ans. Grouping of various malocclusions into a simpler or smaller divisions or groups is known as classification. Strang (1938) defined classification as ‘a process of analysing cases of malocclusion for the purpose of segregating them into a smaller number of groups, which are characterized by certain specific and fundamental variations from normal occlusion of the teeth; these variations become in- 12/3/2013 2:49:13 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 48 fluential and deciding factors in providing the fundamental data for the preparation of a systematic and correlated plan of treatment.’ xiv. Transposition—where the teeth have exchanged/interchanged their positions Interarch Malocclusion Advantages of Classifying Malocclusion It helps in: i. Diagnosis and treatment planning ii. Visualizing and understanding the problem associated with malocclusion iii. Ease of communication among the professionals iv. Comparison of the various types of malocclusions Intra-arch malocclusion variations in individual tooth position and malocclusion affecting a group of teeth within an arch Types of malocclusion Interarch malocclusion (malrelation of dental arches to one another upon normal skeletal bases) It occurs in three planes. Interarch malocclusion (in three planes) Sagittal Prenormal occlusion (Lower arch is more forwardly placed when patient bites in centric occlusion.) Postnormal occlusion (Lower arch is more distally placed when patient bites in centric occlusion.) Skeletal malocclusion (malocclusion involving underlying bony bases) Orthodontics-Part-I-2013.indd 48 Includes deep bite and open bite where abnormal vertical relation exists between teeth of U/L arch Deep bite (Overbite— there is excessive overlap between U/L anteriors.) Intra-arch Malocclusion Commonly seen individual teeth malpositions are: i. Buccal inclination or tipping—proclination (when the tooth is outside the line of occlusion) ii. Lingual inclination or tipping—retroclination (when the tooth is inside the line of occlusion) iii. Mesial inclination or tipping—crown tilted mesially or farther forward than normal iv. Distal inclination or tipping—crown tilted distally or backwards than normal v. Buccal displacement—tooth that is bodily moved in labial/buccal direction vi. Lingual displacement—tooth that is bodily moved in lingual direction vii. Mesial displacement—tooth that is bodily moved in mesial direction viii. Distal displacement—tooth that is bodily moved in distal direction ix. Infraversion or infraocclusion—this is a tooth that has not erupted enough as compared to other teeth in the arch. x. Supraversion or supraocclusion—this is a tooth that has overerupted as compared to other teeth in the arch. xi. Rotations—tooth movement around its long axis. xii. Distolingual or mesiobuccal rotation—tooth that has moved around its long axis so that distal aspect is more lingually placed. xiii. Mesiolingual or distobuccal rotation—tooth that has mesial aspect more lingually placed Vertical Open bite (No vertical overlap between U/L teeth either in anterior/ posterior region.) Transverse Example: various types of crossbites (The term ‘crossbite’ refers to abnormal transverse relationship between U/L arches.) Skeletal Malocclusion Due to abnormalities in the maxilla/mandible, defects can be in size, position or relationship between the jaws. It occurs in one or both the jaws and in various combinations. Skeletal malocclusion (in three planes) Sagittal Forward placement of jaw—Prognathism More backward placement of jaw—Retrognathism Vertical Abnormalities in vertical measurements can affect lower facial height Transverse Result of narrowing or widening of jaws, usually referred to as crossbites Simon’s Classification of Malocclusion In Simon’s classification of malocclusion the dental arches are related to three planes: i. Anteroposterior ii. Transverse iii. Vertical planes. 12/3/2013 2:49:13 PM
  • Topic wise Solved Questions of Previous Years 49 In Simon’s system dental arches are related to three anthropometric planes: i. Frankfurt horizontal (FH) plane ii. Orbital plane iii. Midsagittal plane ANGLE’S CLASSIFICATION OF MALOCCLUSION Angle’s three classes of malocclusion Class I Class III Class II FH plane i. Attraction—dental arch or part of it is closer than normal to FH plane ii. Abstraction—when dental arch or part of it is farther away from FH plane Orbital plane i. Protraction—dental arch or part of it is farther away from orbital plane. ii. Retraction—dental arch or part of it is closer or more posterior plane in relation to orbital plane. Midsagittal plane (transverse direction) i. Distraction—Dental arch or part of it is away from midsagittal plane ii. Contraction—Dental arch of part of it is closer to midsagittal plane. Q. 2. Define classification of malocclusion and explain in detail Angle’s classification and its validity. Or, Describe various classifications of malocclusion. Enumerate the merits and demerits of Angle’s classification. Or Describe Angle’s classification of malocclusion and mention the limitations of this classification. Or Discuss in brief Angle’s classification of malocclusion along with its merits, demerits and modifications. Ans. Grouping of various malocclusions into a simpler or smaller divisions or groups is known as classification. Angle’s system of classification has taken into consideration the anteroposterior relationship of the teeth with each other. Angle introduced this classification with the concept of key of occlusion and line of occlusion. Maxillary first permanent molar is considered to be the key of occlusion and is stated that the position of the maxillary first permanent molar is relatively constant. Orthodontics-Part-I-2013.indd 49 Division 1 and Division 2 True class III Pseudo class III Skeletal class III The three classes of Angle’s malocclusion are based on the permanent first molar relationship. Angle’s Class I Malocclusion (Neutrocclusion) Molar relation in Angle’s class I The mesiobuccal cusp of the upper first molar occludes with the mesiobuccal groove of the lower first molar. Canine relation The mesial incline of the upper canine occludes with the distal incline of the lower canine, whereas the distal incline of the upper canine occludes with the mesial incline of lower first premolar. Line of occlusion Line of occlusion will be altered in maxillary and mandibular arches: Individual tooth irregularities like crowding, spacing, rotations, absence of tooth will be seen. Interarch problems like deep bite, open bite, proclination or increased overjet, crossbite will be present. Class I bimaxillary protrusion Class I bimaxillary malocclusion is a condition where both the key of occlusion and line of occlusion are not altered, but the upper and lower anteriors are proclined and exist usually in an edge–edge relationship. Angle’s Class II Malocclusion (Distocclusion) Class II malocclusion has divisions, namely, a. division 1 and b. division 2. Angle’s class II division 1 malocclusion Molar relation Lower dental arch is distally positioned in relation to upper dental arch. The distobuccal cusp of the upper first 12/3/2013 2:49:13 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 50 permanent molar occludes with the mesiobuccal groove of the lower first permanent molar. Angle’s Class III Malocclusion (Mesiocclusion) Class II canine relation Class III malocclusion is a condition in which the lower molar is positioned mesial to the upper molar. The distal incline of upper canine occludes with mesial incline of lower canine. Class III subdivision Other features are: V-shaped or narrow constricted maxilla Proclined maxillary incisors Lip trap Deep bite and exaggerated curve of Spee. Class II division 1 subdivision Condition where the class II molar relationship is unilateral, i.e. present only on one side with normal class I molar occlusion on the other side. Angle’s class II division 2 malocclusion Class II division 2 malocclusion is characterized by class II molar relationship with retroclined upper centrals, which are overlapped by the lateral incisors. It includes variations like retroclined centrals and lateral incisors, and very rarely include retroclined canines as well. Condition in which class III molar relation is present only on one side with normal molar relation on the other side is known as class III subdivision. True class III This is a skeletal malocclusion; it could be due to retrognathic maxilla, prognathic mandible or combination of both. In this class III, molar relation exists both in centric occlusion and at rest position. Pseudo class III/habitual class III This is not a true class III malocclusion. When the mandible moves from rest position to occlusion due to occlusal prematurities, it slides forward into a pseudo class III position. These patients show normal molar relationship in rest position while class III relation in centric occlusion. Class II molar relation Lower dental arch is distally positioned in relation to upper arch. The distobuccal cusp of the upper first molar occludes with the mesiobuccal groove of the lower first molar. Class II canine relation The distal incline of the upper canine occludes with the mesial incline of the lower canine. Line of occlusion Line of occlusion is altered. Other clinical features are: i. Molars in distocclusion ii. Retroclined central incisors and rarely other anteriors as well iii. Deep bite iv. Broad square face with pleasing straight profile v. Square-shaped arch and exaggerated curve of Spee vi. Backward path of closure vii. Deep mentolabial sulcus viii. Absence of abnormal muscle activity. It has perfectly acceptable function as well as facial appearance. In severe cases the bite is often very deep and poses the risk of periodontal trauma in maxillary palatal and mandibular labial aspects. Class II division 2 subdivision Condition when the class II molar relation exists only on one side with normal molar relation on the other side is known as class II division 2 subdivision. Orthodontics-Part-I-2013.indd 50 Clinical features of class III malocclusion Molar relation: Mesiobuccal cusp of the upper first permanent molar occludes with the interdental space between the lower first and second permanent molars. Canine relation: Upper canine occludes with the interdental space between lower first and second premolars. Line of occlusion: May or may not be altered. Reverse overjet or anterior crossbite. Posterior crossbite. True class III and pseudo class III malocclusions can be differentiated by taking a cephalogram in both at rest position and occlusion. Merits and Demerits of Angle’s Classification Merits It is the most popular system of classification of malocclusion. It is the most traditional and oldest system of classification still in use. Easy to communicate. Most practical and easy to comprehend. Widely used for academic purpose. Demerits Angle considered only anteroposterior plane in his system of classification. He did not consider transverse and vertical planes. 12/3/2013 2:49:13 PM
  • Topic wise Solved Questions of Previous Years 51 The position of the maxillary first permanent molar is not stable, as considered by Angle. Classification is not applicable when first permanent molars are missing. Not applicable in deciduous dentition. Consideration is not given to skeletal problems. Angle’s classification considers only static occlusion. Aetiology of the malocclusion is not highlighted. This classification does not differentiate between dentoalveolar and skeletal malocclusions. Angle has not considered individual tooth malpositions. There are two modifications of Angle’s classification; they are: i. Lischer’s modification and ii. Dewey’s modification. As the degree of alignment and symmetry is common to all dentition, it is represented as group 1. It is classified in this step as ideal, crowded or spaced. Crowding, rotations, spacing and mutilated conditions are possible malocclusions in this step. If no abnormality is present, it is called ideal. Group 2—Profile Proceeding inside the Venn diagram—it involves consideration of the profile of the patient. The profile is described as straight, convex and concave. The facial divergence is considered as anterior or posterior divergence. Group 3—Type Q. 3. State how Ackerman and Proffit’s system is an improvement over Angle’s classification. The term ‘type’ is used to describe the kinds of crossbites. Lateral or transverse arch characteristics are evaluated. Ans. Crossbites are classified as: i. Buccal and palatal ii. Unilateral and bilateral iii. Skeletal and dental. ACKERMAN AND PROFFIT’S METHOD Ackerman and Proffit introduced a new method of classification to overcome the defects of Angle’s classification. This system included Angle’s classification and five major characteristics of malocclusion within a Venn symbolic diagram (Fig. 7.1). Buccal Palatal Unilateral Bilateral Dental Skeletal Group 3 transverse deviation (lateral) Group trans-sagittal Alignment Type profile class Group 4 sagittal deviation (A-P) ANT Class I displacement Class II Division 1 Class III Division 2 Dental Skeletal Group 9 Trans-sagitto-vertical Alignment Alignment Alignment Group 8 Group 7 profile class Profile profile VerticoSagitto-vertical Type Class type transverse Alignment Bite Depth Alignment Profile Profile Group 2 Class Type Bite Depth profile Convex Bite depth Group 5 Alignment Straight Vertical deviation profile Concave Open bite Anterior, posterior Anterior Deep bite Anterior divergent Collapsed Posterior Posterior Dental Skeletal divergent Alignment Profile Bite depth Ideal Group 1 crowding Intra-arch spacing alignment-symmetry (occlusal view) Alignment Fig. 7.1 Venn symbolic diagram of Ackerman–Proffit’s system. This is an all-inclusive method of categorizing malocclusion. In this classification, each malocclusion can be described by five major characteristics. Procedure Group 1—Intra-arch alignment and symmetry It involves assessment of alignment and symmetry of dental arches. Individual tooth irregularities are described. Orthodontics-Part-I-2013.indd 51 Group 4—Class It involves assessment of sagittal relationship. It is classified as Angle’s class I/class II/class III malocclusion. Differentiation is made between skeletal and dental malocclusions. Group 5—Bite depth Malocclusion in vertical plane is considered. Patient’s skeletal and dental relationships are analysed for problems in the vertical plane. Vertical deviations: i. Open bite—anterior open bite, posterior open bite, skeletal open bite and dental open bite ii. Deep bite—dental or skeletal, and posterior collapsed bite. The overlapping groups are seen in the centre of the Venn diagram. Group 9 has the most severe form of malocclusion comprising problems in all the three dimensions. Advantages The complexities of malocclusion are explained. In addition to anteroposterior malrelations, transverse as well as vertical discrepancies are taken into consideration, i.e. all three planes are considered. Profile of the patient is given due consideration. Differentiation between skeletal and dental problems is made. 12/3/2013 2:49:13 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 52 This classification helps in complete diagnosis and differential treatment planning. Readily adaptable to the computer processing. Class I Disadvantages Aetiological aspects are not considered in the classification. It is based only on static occlusion, whereas functional occlusion is not considered. Q. 4. Discuss modifications of Angle’s classification of malocclusion in brief. Or Describe Dewey–Anderson’s modification of Angle’s classification in detail. Ans. There are two modifications of Angle’s classification of malocclusion: i. Lischer’s modification and ii. Dewey’s modification. Lischer’s Modification The following names are given by Lischer to Angle’s classification: i. Neutrocclusion—class I ii. Distocclusion—class II iii. Mesiocclusion—class III. To describe malpositions of individual teeth the following nomenclature was given by Lischer, which indicates the direction of deviation from normal position: i. ii. iii. iv. v. vi. vii. viii. ix. ii. Class III is divided into three types. iii. Class II has no types. Mesioversion—mesial to the normal position Distoversion—distal to the normal position Linguoversion—lingual to the normal position Labioversion/buccoversion—towards the lip or cheek Infraversion—away from the line of occlusion Supraversion—crossing the line of occlusion Axiversion—wrong axial inclination Torsiversion—rotated on its long axis Transiversion-transposition—wrong position in the arch. i. Type 1: Crowded maxillary anterior teeth. Canines may be abnormally positioned. Other individual teeth irregularities present. ii. Type 2: Proclined or labioversion of maxillary central and lateral incisors. iii. Type 3: Class I with anterior crossbite present. iv. Type 4: Class I with posterior crossbite present. Molars and premolars are in buccoversion. v. Type 5: Mesioversion of molars. Class III i. Type 1: Well-aligned teeth and dental arches. Edge–edge relationship exists. ii. Type 2: Crowded mandibular incisors. Normally placed lower incisors behind the upper incisors. iii. Type 3: Crowded maxillary incisors. Underdeveloped maxilla anterior crossbite present. Q. 5. Describe Angle’s class II division 1 malocclusion. Discuss how it differs with Angle’s class II division 2 malocclusion. Or Describe the characteristics of class II division 1 and class II division 2 malocclusions. Ans. Differences between class II division 1 and class II division 2 malocclusions are as follows: Martin Dewey has further divided Angle’s class I and III into various types: i. Class I is divided into five types. Orthodontics-Part-I-2013.indd 52 Class II division 1 Class II division 2 i. Profile Convex Straight to mild convexity ii. Lips Incompetent short upper lip and everted lower lip Competent normal upper and lower lips iii. Mentolabial sulcus Deep Normal or may be deep sometimes iv. Mentalis muscle Dewey’s Modification Feature Hyperactive Normal v. Molar process Not prominent Prominent vi. Lower facial height Normal or may be in- Decreased creased or decreased vii. Arch form ‘V’ shaped ‘U’ shaped or square shaped 12/3/2013 2:49:13 PM
  • Topic wise Solved Questions of Previous Years 53 Feature Class II division 1 Class II division 2 iii. Premature con- Absent tacts viii. Palate Deep Normal iv. Path of closure Forward Deviated Central incisors are retroclined; lateral incisors are proclined v. Gonial angle ↑or ↓ Normal ix. Incisors (maxillary) Proclined x. Overjet Increased xi. Overbite Deep overbite vi. Retrusion of man- Not possible dible Possible vii. Treatment Elimination of prematurities and replacement of last posterior teeth by functional space maintainers If left untreated it becomes established into true class III malocclusion Decreased Closed bite xii. Crown–root angu- Normal lation Axis of crown and root is bent and is referred to as collum angle xiii. Path of closure Backward path of closure Normal Q. 6. Enumerate the differences between true class III and pseudo class III malocclusions. Ans. Differences between true class III and pseudo class III malocclusions are as follows: Feature True class III Pseudo class III i. Profile Concave Straight or concave ii. Aetiology Heredity Habitual or developmental Present Orthopaedic or surgical correction No further changes occur if left untreated Surgical procedures that can be carried out for skeletal class III malocclusion are as follows: i. Le Fort I osteotomy—for maxillary deficiency ii. Osteotomy of the mandible iii. Sliding osteotomy in ramus or body of the mandible iv. Sagittal split osteotomy—to correct mandibular prognathism v. Genioplasty—to correct chin prominence. These skeletal procedures have to be modified according to the vertical malrelation, i.e. associated open bite or deep bite. SHORT ESSAYS Q. 1. Ackerman–Proffit’s classification of malocclusion Ans. Ackerman and Proffit introduced a new method of classification to overcome the defects of Angle’s classification. This system included Angle’s classification and five major characteristics of malocclusion within a Venn symbolic diagram. The facial divergence is considered as anterior or posterior divergence. Group 3—Type The term ‘type’ is used to describe the kinds of crossbites. Procedure Crossbites are classified as: i. Buccal and palatal ii. Unilateral and bilateral iii. Skeletal and dental. Group 1—Intra-arch alignment and symmetry It involves assessment of alignment and symmetry of dental arches. It is classified in this step as ideal, crowded or spaced. Group 4—Class It involves assessment of sagittal relationship. It is classified as Angle’s class I/class II/class III malocclusion. Group 2—Profile The profile is described as straight, convex and concave. Group 5—Bite depth Malocclusion in vertical plane is considered. Orthodontics-Part-I-2013.indd 53 12/3/2013 2:49:13 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 54 Vertical deviations: i. Open bite—anterior open bite, posterior open bite, skeletal open bite and dental open bite ii. Deep bite—dental or skeletal, and posterior collapsed bite. The overlapping groups are seen in the centre of Venn diagram. Group 9 will have the most severe form of malocclusion comprising problems in all the three dimensions. Q. 2. Angle’s class II division 1 malocclusion—clinical features The position of the maxillary first permanent molar is not stable, as considered by Angle. Classification is not applicable when first permanent molars are missing. Not applicable in deciduous dentition. Consideration is not given to skeletal problems. Angle’s classification considers only static occlusion. Aetiology of the malocclusion is not highlighted. This classification does not differentiate between dentoalveolar and skeletal malocclusions. Angle has not considered individual tooth malpositions. Ans. Q. 4. Angle’s classification of malocclusion Angle’s class II malocclusion has two divisions, namely, division 1 and division 2. Ans. Angle’s class II division 1 malocclusion Class II division 1 malocclusion is characterized by class II molar relation with proclined maxillary anterior teeth. Clinical features Class II molar relation: Lower dental arch is distally positioned in relation to upper dental arch. The distobuccal cusp of the upper first permanent molar occludes with the mesiobuccal groove of the lower first permanent molar. Class II canine relation: The distal incline of upper canine occludes with mesial incline of lower canine. Proclined maxillary anteriors with a V-shaped or narrow constricted maxilla. Convex profile. Increased overjet, deep bite and exaggerated curve of Spee. Short hypotonic upper lip, lip trap and lack of anterior lip seal. Patient exhibits abnormal muscle activity. Proclined lower anteriors—a natural compensation to decrease overjet. Class II division 1 subdivision Condition where the class II molar relationship is unilateral, i.e. present only on one side with normal class I molar occlusion on the other side. Angle’s system of classification has taken into consideration the anteroposterior relationship of the teeth with each other. Angle introduced this classification with the concept of key of occlusion and line of occlusion. Maxillary first permanent molar is considered to be the key of occlusion and is stated that the position of the maxillary first permanent molar is relatively constant. ANGLE’S CLASSIFICATION Angle’s three classes of malocclusion Angle’s three classes of malocclusion Class I Class III Class II Division 1 and Division 2 True class III Pseudo class III Skeletal class III The three classes of Angle’s malocclusion are based on the permanent first molar relationship. Angle’s Class I Malocclusion (Neutrocclusion) Molar relation in Angle’s class I Q. 3. Drawbacks of Angle’s classification Or Limitations of Angle’s classification Ans. Drawbacks of Angle’s classification Angle considered only anteroposterior plane in his system of classification. He did not consider transverse and vertical planes. Orthodontics-Part-I-2013.indd 54 The mesiobuccal cusp of the upper first molar occludes with the mesiobuccal groove of the lower first molar. Individual tooth irregularities like crowding, spacing, rotations, absence of tooth will be seen. Interarch problems like deep bite, open bite, proclination or increased overjet, crossbite will be present. Class I bimaxillary protrusion Class I bimaxillary malocclusion is a condition where both the key of occlusion and line of occlusion are not altered, but 12/3/2013 2:49:13 PM
  • Topic wise Solved Questions of Previous Years 55 the upper and lower anteriors are proclined and exist usually in an edge–edge relationship. Angle’s Class II Malocclusion (Distocclusion) In Angle’s class II malocclusion the lower dental arch is distally positioned in relation to upper arch. The distobuccal cusp of the upper first permanent molar occludes with the mesiobuccal groove of the lower first permanent molar. Class II malocclusion has got two divisions, namely, division 1 and 2. Q. 5. Characteristics of Angle’s class II division 2 malocclusion Or Clinical features of class II division 2 malocclusion Ans. Angle’s class II division 2 malocclusion Class II division 2 malocclusion is characterized by class II molar relationship with retroclined upper centrals that are overlapped by the lateral incisors. Angle’s class II division 1 malocclusion Class II molar relation Class II division 1 malocclusion is characterized by class II molar relation with proclined maxillary anterior teeth. Lower dental arch is distally positioned in relation to upper arch. The distobuccal cusp of the upper first molar occludes with the mesiobuccal groove of the lower first molar. Angle’s class II division 2 malocclusion Class II division 2 malocclusion is characterized by class II molar relationship with retroclined upper centrals that are overlapped by the lateral incisors. Includes variations like retroclined centrals, lateral incisors and very rarely include retroclined canines as well. Class II division 1 subdivision or class II division II subdivision Condition when the class II molar relation exists on only one side with normal molar relation on the other side is known as class II division 1 or division 2 subdivision. Angle’s Class III Malocclusion (Mesiocclusion) Class III malocclusion is a condition in which the lower molar is positioned mesial to the upper molar. True class III This is a skeletal malocclusion; it could be due to retrognathic maxilla, prognathic mandible or combination of both. In this class III, molar relation exists both in centric occlusion and at rest position. Pseudo class III/habitual class III This is not a true class III malocclusion. When the mandible moves from rest position to occlusion due to occlusal prematurities, it slides forward into a pseudo class III position. These patients show normal molar relationship in rest position while class III relation in centric occlusion. Class II canine relation The distal incline of the upper canine occludes with the mesial incline of the lower canine. Line of occlusion Line of occlusion is altered. Other clinical features Molars in distocclusion Retroclined central incisors and rarely other anteriors as well Deep bite Broad square face with pleasing straight profile Square-shaped arch and exaggerated curve of Spee Backward path of closure Deep mentolabial sulcus Absence of abnormal muscle activity. They have perfectly acceptable function as well as facial appearance. In severe cases, the bite is often very deep and poses the risk of periodontal trauma in maxillary palatal and mandibular labial aspects. Q. 6. Simon’s classification of malocclusion Ans. In Simon’s classification of malocclusion the dental arches are related to three planes: i. Anteroposterior ii. Transverse iii. Vertical planes. Class III subdivision In Simon’s system dental arches are related to three anthropometric planes: i. Frankfurt horizontal (FH) plane ii. Orbital plane iii. Midsagittal plane. Condition in which class III molar relation is present only on one side with normal molar relation on the other side is known as class III subdivision. FH plane i. Attraction: Dental arch or part of it is closer than normal to FH plane Orthodontics-Part-I-2013.indd 55 12/3/2013 2:49:13 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 56 ii. Abstraction: When dental arch or part of it is farther away from FH plane. Orbital plane (Simon’s law of canines) i. Protraction: Dental arch or part of it is farther away from orbital plane ii. Retraction: Dental arch or part of it is closer or more posterior plane in relation to orbital plane. Midsagittal plane (transverse direction) i. Distraction: Dental arch or part of it is away from midsagittal plane ii. Contraction: Dental arch of part of it is closer to midsagittal plane. Q. 7. Dewey’s classification of malocclusion Or Dewey’s modification of Angle’s classification Ans. Class III i. Type 1: Well-aligned teeth and dental arches. Edge–edge relationship exists. ii. Type 2: Crowded mandibular incisors. Normally placed lower incisors behind the upper incisors. iii. Type 3: Crowded maxillary incisors. Underdeveloped maxilla anterior crossbite present. Q. 8. Pseudo class III malocclusion Ans. Class III malocclusion is a condition in which the lower molar is positioned mesial to the upper molar. Pseudo class III/habitual class III is not a true class III malocclusion. When the mandible moves from rest position to occlusion due to occlusal prematurities, it slides forward into a pseudo class III position. These patients show normal molar relationship at rest position while class III relation in centric occlusion. Dewey’s modification of Angle’s classification Aetiology Martin Dewey has further divided Angle’s class I and class III into various types: Class I is divided into five types. Class III is divided into three types. Class II has no types. Habitual or developmental. Class I i. Type 1: Crowded maxillary anterior teeth. Canines may be abnormally positioned. Other individual teeth irregularities present. ii. Type 2: Proclined or labioversion of maxillary central and lateral incisors. iii. Type 3: Class I with anterior crossbite present. iv. Type 4: Class I with posterior crossbite present. Molars and premolars are in buccoversion. v. Type 5: Mesioversion of molars. Clinical features The clinical features of pseudo class III malocclusion are as follows: Profile is either straight or concave. Premature contacts and deviated path of closure are present. Gonial angle is normal. Retrusion of mandible is possible. Treatment Treatment of pseudo class III consists of elimination of prematurities and replacement of last posterior teeth by functional space maintainers. If left untreated it becomes established into true class III malocclusion. SHORT NOTES Q. 1. Bennett classification Ans. Norman Bennett classified malocclusion based on its aetiology as follows: i. Class I: Malocclusion or abnormal position of one or more teeth due to local causes. ii. Class II: Malocclusion due to developmental defects of bone in either of the arch. Orthodontics-Part-I-2013.indd 56 iii. Class III: Malocclusion due to abnormal relationship between upper and lower arches and between either arches and facial contour and correlated abnormal formation of either arches. Q. 2. Simon’s classification of malocclusion Ans. Simon had put forward a craniometric classification of malocclusion using three anthropometric planes, i.e. the 12/3/2013 2:49:14 PM
  • Topic wise Solved Questions of Previous Years 57 Frankfurt horizontal (FH) plane, the orbital plane and the midsagittal plane. The classification of malocclusion was based on abnormal deviations of the dental arches from their normal position in relation to these three planes. FH plane i. Attraction: Dental arch or part of it is closer than normal to FH plane ii. Abstraction: When dental arch or part of it is farther away from FH plane. Orbital plane i. Protraction: Dental arch or part of it is farther away from orbital plane ii. Retraction: Dental arch or part of it is closer to orbital plane. Midsagittal plane i. Distraction: Dental arch or part of it is away from mid sagittal plane ii. Contraction: Dental arch of part of it is closer to mid sagittal plane. Q. 3. Validity of Angle’s classification Or Drawbacks of Angle’s classification Or Mention two merits and demerits of Angle’s classification. Ans. Frankfurt horizontal (FH) plane or eye–ear plane (EEP) is obtained by drawing a line through the margin of inferior orbit below the eye ball and upper margin of auditory meatus. This plane helps to detect deviations in the vertical plane. Height of the dental arches and teeth is related to the cranium. Dental arch closer to this plane is called attraction and farther away from this plane is called abstraction. Q. 5. Pseudo class III malocclusion Ans. Pseudo class III/habitual class III is not a true class III malocclusion. When the mandible moves from rest position to occlusion due to occlusal prematurities, it slides forward into a pseudo class III position. These patients show normal molar relationship at rest position while class III relation in centric occlusion. It is habitual or developmental in origin. Profile is either straight or concave with premature contacts and deviated path of closure. Retrusion of mandible is possible. Treatment of pseudo class III consists of elimination of prematurities and replacement of last posterior teeth by functional space maintainers. Q. 6. Clinical features of class III malocclusion Ans. Merits It is most popular, traditional and oldest system of classification of malocclusion. Easy to communicate and most practical. Widely used for academic purpose. Demerits Angle considered only anteroposterior plane in his system of classification. The position of the maxillary first permanent molar is not stable, as considered by Angle. Classification is not applicable when first permanent molars are missing and also in deciduous dentition. Consideration is not given to skeletal problems and individual tooth malpositions. It considers only static occlusion, and aetiology of the malocclusion is not highlighted. It does not differentiate between dentoalveolar and skeletal malocclusions. Q. 4. FH plane Orthodontics-Part-I-2013.indd 57 Or True class III Ans. Angle’s class III malocclusion (mesiocclusion) is a condition in which the lower molar is positioned mesial to the upper molar. True class III is a skeletal malocclusion; it could be due to retrognathic maxilla, prognathic mandible or combination of both. Here class III molar relation exists both in centric occlusion and at rest position. Clinical features of class III malocclusion Molar relation: Mesiobuccal cusp of the upper 1st permanent molar occludes with the interdental space between the lower first and second permanent molars. Canine relation: Upper canine occludes with the interdental space between lower first and second premolars. Line of occlusion: May or may not be altered. Reverse overjet or anterior crossbite and posterior crossbite. Concave profile. 12/3/2013 2:49:14 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 58 Q. 7. Clinical features of class II division 2 malocclusion Step 2 (profile): The profile is described as straight, convex and concave. Ans. Step 3 (type): The term ‘type’ is used to describe the various kinds of crossbites like buccal and palatal, unilateral and bilateral, or skeletal and dental. Angle’s class II division 2 malocclusion is characterized by class II molar relationship with retroclined upper centrals that are overlapped by the lateral incisors. Clinical features Molars in distocclusion Retroclined central incisors l Deep bite Broad square face with pleasing straight profile Backward path of closure Deep mentolabial sulcus Absence of abnormal muscle activity. They have perfectly acceptable function as well as facial appearance. Q. 8. Define malocclusion. Name few classifications of malocclusion. Or Name different classifications of malocclusion. Or Enlist various systems of classification of malocclusion. Ans. Malocclusion is defined as a condition where there is departure from normal relation of teeth in the same arch and to teeth in opposing arch. Qualitative methods of classification i. Angle’s classification ii. Simon’s classification iii. Bjork’s classification iv. Ackerman–Proffit classification v. Bennett classification, etc. Quantitative methods of classification i. Massler and Frankel ii. Occlusal index by Summers’ iii. Occlusal feature index by Poulton iv. Index for orthodontic treatment need by Shaw, etc. Q. 9. Ackerman–Proffit’s classification Ans. Ackerman and Proffit introduced a new method of classification system, which included Angle’s classification and five major characteristics of malocclusion within a Venn symbolic diagram. The Venn diagram is analysed in following steps: Step 1 (assessment of intra-arch alignment and symmetry): It is classified as ideal, crowded or spaced. Orthodontics-Part-I-2013.indd 58 Step 4 (class): Assessment of sagittal relationship. It is classified as Angle’s class I/class II/class III malocclusion. Step 5 (bite depth): Vertical plane is considered. i. Open bite—anterior, posterior, skeletal or dental ii. Deep bite—dental or skeletal, and posterior collapsed bite. The overlapping groups are seen in the centre of Venn diagram. It has the most severe form of malocclusion comprising problems in all the three dimensions. Q. 10. Features of class II division 1 malocclusion Ans. Angle’s class II division 1 malocclusion Class II division 1 malocclusion is characterized by class II molar relation, i.e. the distobuccal cusp of the upper first permanent molar occludes with the mesiobuccal groove of the lower first permanent molar with proclined maxillary anterior teeth. Clinical features Convex profile. Increased overjet, deep bite and exaggerated curve of Spee. Short hypotonic upper lip, lip trap and lack of anterior lip seal. Patient exhibits abnormal muscle activity. Proclined lower anteriors—a natural compensation to decrease overjet. Q. 11. Distocclusion Ans. Angle’s class II malocclusion is known as distocclusion. In class II molar relation, the distobuccal cusp of the upper first molar occludes with the mesiobuccal groove of the lower first molar. Class II malocclusion has two divisions, namely, division 1 and division 2. Angle’s class II division 1 malocclusion Class II division 1 malocclusion is characterized by class II molar relation with proclined maxillary anterior teeth. Angle’s class II division 2 malocclusion Class II division 2 malocclusion is characterized by class II molar relationship with retroclined upper centrals that are overlapped by the lateral incisors. 12/3/2013 2:49:14 PM
  • Topic wise Solved Questions of Previous Years 59 Class II division 1 or 2 subdivision Condition when the class II molar relation exists on only one side with normal molar relation on the other side is known as class II division 1 or 2 subdivision. Q. 12. Lischer’s modifications of Angle’s classification Ans. Lischer’s modifications of Angle’s classification of malocclusion The following names are given by Lischer to Angle’s classification: i. Neutrocclusion—class I ii. Distocclusion—class II iii. Mesiocclusion—class III. To describe malpositions of individual teeth the following nomenclature was given by Lischer, which indicates the direction of deviation from normal position. i. Mesioversion and distoversion ii. Linguoversion and labioversion/buccoversion iii. Infraversion and supraversion iv. Axiversion, torsiversion and transiversion. Q. 13. Skeletal classification of malocclusions Ans. Skeletal classification is based on the facial skeletal pattern and also relationship of teeth. i. Skeletal class I: The bones of the face, maxilla and mandible are in normal relation to each other. ii. Skeletal class II: Mandibular development is retarded when compared to the maxilla. Distal relationship of mandible to maxilla. iii. Skeletal class III: Increased growth of mandible with prognathic profile. Q. 14. Mention two differences between true and pseudo class III malocclusions. Q. 15. Mention three planes used in Simon’s classification. Ans. In Simon’s system dental arches are related to three anthropometric planes. Simon had put forward a craniometric classification of malocclusion using three anthropometric planes, i.e. i. The Frankfurt horizontal plane ii. The orbital plane and iii. The midsagittal plane. Q. 16. Dewey’s modification of Angle’s classification of malocclusion Ans. Dewey’s modification of Angle’s classification Martin Dewey has further divided Angle’s class I and III into various types. Class I It is divided into five types. i. Type 1: Crowded maxillary anterior teeth. ii. Type 2: Proclined or labioversion of maxillary central and lateral incisors. iii. Type 3: Class I with anterior cross bite present. iv. Type 4: Class I with posterior cross bite present. v. Type 5: Mesioversion of molars. Class II It has no types. Class III It is divided into three types. i. Type 1: Well-aligned teeth and dental arches. Edge–edge relationship exists. ii. Type 2: Crowded mandibular incisors. iii. Type 3: Crowded maxillary incisors. Ans. Q. 17. Key ridge The differences between true and pseudo class III malocculusions are as follows: Ans. Feature True class III Pseudo class III i. Profile Concave Straight or concave ii. Premature contacts Absent Present iii. Path of closure Forward Deviated iv. Gonial angle ↑ or ↓ Normal v. Retrusion of mandible Not possible Orthodontics-Part-I-2013.indd 59 Possible Key ridge is the inferiormost point of anterior border of bony buttress of zygoma. Angle said that maxillary first molar is most constant in position and related it to key ridge position. Angle’s conviction was supported by Atkinson, who suggested a relative constancy of maxillary first molar and the bony buttress of the zygoma, which he called the key ridge. 12/3/2013 2:49:14 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 60 Topic 8 AETIOLOGY OF MALOCCLUSION LONG ESSAYS Q. 1. Define malocclusions. Discuss aetiology of malocclusion. Or Explain in detail aetiology of malocclusion. Or Classify the aetiology of malocclusion. Discuss general factors in detail. Ans. According to Gardiner, White and Leighton malocclusion is defined as a condition in which there is a departure from the normal occlusion of the teeth to other teeth within the same arch and to the teeth in the opposing arch. d. Posture e. Nail biting f. Other habits vi. Diseases a. Systemic diseases b. Endocrine disorders c. Local diseases Nasopharyngeal diseases and disturbed respiratory function Gingival and periodontal disease Tumours Caries vii. Malnutrition White and Gardiner Classification Aetiology of malocclusion Broadly aetiological factors are classified as: i. Genetic factors ii. Environmental factors. Graber has classified aetiological factors as: i. General factors ii. Local factors. CLASSIFICATION OF AETIOLOGY OF MALOCCLUSION Moyer’s Classification i. Heredity a. Neuromuscular system b. Bone c. Teeth d. Soft parts ii. Developmental defects of unknown origin iii. Trauma a. Prenatal trauma and birth injuries b. Postnatal trauma iv. Physical agents a. Premature extraction of primary teeth b. Nature of food v. Habits a. Thumb sucking and finger sucking b. Tongue thrusting c. Lip sucking and lip biting Orthodontics-Part-I-2013.indd 60 Dental base abnormalities i. Anteroposterior malrelationship ii. Vertical malrelationship iii. Lateral malrelationship iv. Disproportion of size between teeth and basal bone v. Congenital abnormalities Pre-eruption abnormalities i. Abnormalities in position of developing tooth germ ii. Missing teeth iii. Supernumerary teeth and teeth abnormal in form iv. Prolonged retention of deciduous teeth v. Large labial frenum vi. Traumatic injury Posteruption abnormalities i. Muscular a. Active muscle force b. Rest position of musculature c. Sucking habits d. Abnormalities in path of closure ii. Premature loss of deciduous teeth iii. Extraction of permanent teeth Q. 2. Discuss the environmental or local causes of malocclusion. Ans. Various environmental or local factors that cause malocclusion are as follows: A. Disturbances of dental development a. Supernumerary teeth b. Supplemental teeth c. Missing teeth 12/3/2013 2:49:14 PM
  • Topic wise Solved Questions of Previous Years 61 Graber’s Classification of Malocclusion General factors 1. Heredity Local factors Supernumerary teeth 1. Anomalies of number Missing teeth (congenital absence of loss due to accidents, caries, etc.) 2. Congenital 3. Environmental Prenatal (trauma, maternal diet and metabolism, German measles) Postnatal (birth injury, cerebral palsy, TMJ injury) 4. Predisposing metabolic and climatic diseases a. Endocrine imbalance b. Metabolic disturbances c. Infectious diseases 5. Dietary problems (nutritional deficiency) 6. Abnormal pressure habits and functional aberrations a. Abnormal sucking b. Thumb/finger sucking c. Tongue thrust/tongue sucking d. Lip and nail biting e. Abnormal swallowing habits (improper deglutition) f. Speech defects g. Respiratory abnormalities (mouth breathing) h. Tonsils and adenoids i. Psychogenicities and bruxism 7. Posture 8. Trauma and accidents ii. Anomalies of tooth size iii. Anomalies of tooth shape iv. Premature loss of deciduous teeth v. Prolonged retention of deciduous teeth vi. Delayed eruption of permanent teeth vii. Abnormal eruptive path B. Trauma to the teeth C. Mucosal barriers i. Abnormal labial frenum attachment ii. Soft tissue impaction D. Dental caries E. Improper dental restoration. A. Disturbances of Dental Development i. Anomalies in number of teeth a. Supernumerary teeth b. Supplemental teeth c. Missing teeth Orthodontics-Part-I-2013.indd 61 2. Anomalies of tooth size 3. Anomalies of tooth shape 4. Abnormal labial frenum: mucosal barriers 5. Premature loss of deciduous teeth 6. Prolonged retention of teeth 7. Delayed eruption path 8. Abnormal eruptive path 9. Ankylosis 10. Dental caries 11. Improper dental restoration a. Supernumerary teeth Teeth that are extra to the normal complement are known as supernumerary teeth. They do not resemble normal teeth and are usually conical in shape. They can occur singly or as pair. Examples: Mesiodens, paramolars, etc. Mesiodens is most frequently seen supernumerary teeth. b. Supplemental teeth Extra teeth that resemble normal teeth are called supplemental teeth. Example: Most often seen in 245 region. 245 Effects of supernumerary and supplemental teeth are as follows: ❍ They cause non-eruption of adjacent teeth. ❍ They deflect erupting adjacent teeth into abnormal location. ❍ They can result in crowding and rotation of adjacent teeth. 12/3/2013 2:49:14 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 62 ❍ ❍ Unerupted mesiodens is one of the causes of midline spacing. Unerupted supernumerary teeth are potential risk factors for cystic transformation. c. Missing teeth Congenitally missing teeth are far more common than supernumerary teeth. Some of the commonly missing teeth in decreasing order of frequency are: third molars, 2 2, 5 5 , 1 1 and 5 5 These can be unilateral or bilateral. Spacing in dental arches. Migration of adjacent teeth—abnormal location and axial inclination of teeth. Overretained deciduous teeth—because of absence of permanent teeth. ii. Anomalies of tooth size Increase in size of teeth results in crowding, e.g. fusion between two adjacent teeth and also between normal tooth and supernumerary tooth. Smaller size teeth result in spacing, e.g. commonly seen 2 2 are smaller size . Size of teeth is to a large extent ‘genetically’ determined. Most of these conditions show ‘positive’ family history. iii. Anomalies of tooth shape Anomalies of tooth size and shape are interrelated; frequently seen tooth shape anomalies are peg shaped. Peg2 2 are accompanied by spacing and shaped anomalies migration of teeth. Abnormally large cingulum on a maxillary incisor tooth prevents establishment of normal overbite and overjet, and involved tooth is in labioversion due to forces of occlusion. Additional lingual cusp on 5 5 increases MD dimensions of tooth. Congenital syphilis causes peg laterals and mulberry molars. Developmental defects like amelogenesis imperfecta, hypoplasia of teeth, fusion and gemination causes anomalies of shape. Dilaceration is characterized by abnormal angulation between crown and root of a tooth, or angulation within the root. Dilacerated teeth fail to erupt to normal level and can cause malocclusion. Orthodontics-Part-I-2013.indd 62 iv. Premature loss of deciduous teeth It refers to loss of a tooth before its permanent successor is sufficiently advanced in development and eruption to occupy its place. The severity of malocclusion caused due to early loss of a deciduous tooth depends on following factors: a. Premature loss of deciduous molars predispose to malocclusion due to shifting of adjacent teeth into the space. b. The earlier the deciduous teeth are extracted before successional teeth are ready to erupt the greater is the possibility of malocclusion. c. In cases of arch length deficiency or crowding, the early loss of deciduous teeth worsens the existing malocclusion. v. Prolonged retention of deciduous teeth It is a condition where there is undue retention of deciduous teeth beyond the usual eruption age of their permanent successors. Prolonged retention of deciduous teeth Buccal teeth Anteriors Result in Lingual or palatal eruption of their permanent successors Result in Eruption of permanent teeth either buccally or lingually, or may remain impacted Aetiology for prolonged retention of deciduous teeth: a. Absence of underlying permanent teeth b. Endocrinal disturbances, e.g. hypothyroidism c. Ankylosed deciduous teeth that fail to resorb d. Non-vital deciduous teeth that do not resorb. vi. Delayed eruption of permanent teeth Delayed eruption of permanent teeth may be caused due to: a. Congenital absence of permanent tooth. b. Supernumerary tooth blocking eruption of permanent tooth. c. Presence of a heavy mucosal barrier. d. Premature loss of deciduous tooth (because of formation of bone overerupting permanent tooth). e. Endocrinal disorders—hypothyroidism delays eruption of teeth. f. Presence of deciduous root fragments—those are not resorbed and can block erupting permanent teeth. vii. Abnormal eruptive path The abnormal path of eruption may be caused due to: i. Arch length deficiency 12/3/2013 2:49:14 PM
  • Topic wise Solved Questions of Previous Years 63 ii. Presence of supernumerary teeth or retained root fragments iii. Formation of bony barrier. Example: 3 3 most often found erupting in abnormal position as they develop almost near the floor of the orbit and travel down to their final position in oral cavity. E. Improper Dental Restoration i. Improper occlusal restoration Overcontoured restoration leads to premature contacts and functional shift of mandible during jaw closure. Undercontoured restoration permits supraeruption of opposing dentition. ii. Proximal restoration B. Trauma to the Teeth Trauma to primary teeth may cause displacement of permanent teeth, defective enamel formation or dilacerated roots. Trauma to permanent teeth may result in ankylosis, nonvitality and displacement of tooth. In ankylosis, a part or whole of the root surface is directly fused to bone in the absence of intervening periodontal membrane. Ankylosed teeth fail to erupt to normal level (submerged teeth within jaws) and cause migration of adjacent teeth into the space. C. Mucosal Barriers i. Abnormal labial frenum attachment Abnormalities of maxillary labial frenum are quite often associated with a maxillary midline spacing. Rarely a heavy fibrous frenum is found attached to the interdental papilla region. This can prevent the two max1 1 illary central incisors from approximating each other. Diagnosed by a positive blanch test. A midline IOPA or occlusal radiograph exhibits notching of the interdental alveolar crest. ii. Soft tissue impaction Thick mucosal tissue covering erupting teeth acts as a barrier to path of eruption and results in soft tissue impaction. D. Dental Caries Dental caries Undercontoured restoration leads to loss of arch length and food lodgement. Overcontoured restorations consume more space leading to irregularity of dentition. Q. 3. Enumerate various postnatal causes of malocclusion. Elaborate endocrinal factors. Ans. Various postnatal causes of malocclusion are categorized into: A. Developmental disturbances i. Endocrine disturbances ii. Nutritional deficiencies iii. Allergy iv. Muscular activity v. TMJ problems. B. Functional disturbances i. Head and tongue postures ii. Various habits like mouth breathing, thumb sucking, tongue thrusting and abnormal swallowing, etc. iii. Functional shifts. C. Environmental interferences i. Disturbances of dental development a. Missing teeth b. Malformed teeth c. Supernumerary and supplemental teeth d. Delayed eruption e. Ectopic eruption f. Early loss of primary teeth. ii. Trauma to teeth iii. Dental caries iv. Mucosal barrier, e.g. persistent labial frenum. Endocrine disturbances or problems and their manifestations Premature loss of deciduous/permanent teeth Causes Migration of contiguous teeth Abnormal axial inclination and supraeruption of opposing teeth Orthodontics-Part-I-2013.indd 63 i. Hypopituitarism In hypopituitary dwarfism, the eruption rate and shedding time of teeth are delayed and as is the growth of the body, in general. The dental arch is smaller than normal and cannot accommodate all the teeth; hence the malocclusion develops. Development of maxilla is not as retarded as mandible hence it results in class II. 12/3/2013 2:49:14 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 64 Thickening of dentinal walls at the expense of pulp chambers, amelogenesis directly depends on pituitary hormones, but dentinogenesis and cementogenesis can proceed at decreased rate without pituitary hormones. ii. Hyperpituitarism It results in gigantism and acromegaly. Gigantism is due to hypersecretion of GH (growth hormone) in childhood before fusion of epiphysis of bone with shaft. Acromegaly is due to hypersecretion of GH in adults. Enlargement of bones (especially mandible), kyphosis (bowing of spine) and bull dog scalp are the important features. Gigantism is characterized by a general symmetric overgrowth of the body. Skeletal changes include enlarged supraorbital ridges and prognathic mandible, enlargement of the tongue and whole face. Patients may develop class III malocclusion with interdental spacing. Mandibular prognathism, labial or buccally tilted teeth and enlarged tongue are the features of acromegaly. iii. Hypothyroidism (cretinism) Congenital hypothyroidism or cretinism leads to stunted height, enlargement of tongue and spaced dentition, and delayed dental age. Constant protrusion of enlarged tongue leads to malocclusion. The eruption rate of teeth is delayed and deciduous teeth are retained beyond normal shedding time. iv. Hyperthyroidism This condition is characterized by increase in the rate of maturation and metabolic rate. The patient exhibits premature eruption of deciduous teeth, disturbed root resorption of deciduous teeth and accelerated eruption of permanent teeth. The patient may have osteoporosis, which contraindicates orthodontic treatment. Rare in children. Hypertension, wide staring eyes, anxious looks, very poor dental patients. v. Hypoparathyroidism It is associated with changes in calcium metabolism. It can cause delay in tooth eruption, altered tooth morphology, delayed eruption of deciduous and permanent teeth, and hypoplastic teeth. Morphology of teeth is affected. vi. Hyperparathyroidism It produces increase in blood calcium. There is demineralization of bone and disruption of trabecular pattern. In growing children tooth development is interrupted. The teeth may become mobile due to loss of lamina dura, cortical bone and resorption of the alveolar process. Orthodontics-Part-I-2013.indd 64 Q. 4. Discuss the genetic and hereditary factors contributing towards the formation of malocclusion. Or Role of genetics in malocclusion Ans. Genetic disorders Conditions that are caused due to disturbances in germ plasma or chromosomes or genes are known as genetic disorders. Genetic disorders can be classified into: (i) hereditary and (ii) mutational. i. Hereditary disorders The conditions that are transmitted from one generation to another are known as hereditary disorders. Neel’s criteria for considering a problem as hereditary disorder are: Occurrence of disease in definite numerical proportions among individuals related by descent Failure of disease to spread to non-related individuals Unknown precipitation factor Greater concordance of disorder in identical twins. ii. Mutational disorders In a previously unaffected individual the mutational disorders arise de novo as a result of damage to the germ plasma. If mutational disorders are transmitted to the future generation, it becomes hereditary. Types of transmission of malocclusion Malocclusions are transmitted by three ways: i. Repetitive ii. Discontinuous iii. Variable. i. Repetitive: Recurrence of a single dentofacial deformity within the immediate family. ii. Discontinuous: Recurrence of tendency for a malocclusal trait to reappear after few generations. Some generations will be skipped. iii. Variable: Expression of different but related types of malocclusion within the several generations of the same family. Genetic influence Malocclusions could be produced by heredity in two major possible ways: i. Inherited disproportion between size of teeth and size of jaws. ii. Inherited disproportion between sizes or shapes of upper and lower jaws, which leads to occlusal malrelationships. 12/3/2013 2:49:14 PM
  • Topic wise Solved Questions of Previous Years 65 Genetic disorders seen at the time of birth are called congenital defects. Heredity plays a role in following conditions: i. Congenital deformities ii. Facial asymmetry iii. Cleft lip and palate iv. Mandibular prognathism and retrognathism v. Micrognathia and macrognathia vi. Variations of tooth shape. Various modes of inheritance are: i. Autosomal dominance and recessive ii. X-linked iii. Polygenic iv. Chromosomal. Contemporary views on aetiology of malocclusion attribute some of the malocclusions to hereditary or genetic causes. Dental problems Crowding—hereditary and environmental reasons Individual tooth malalignments and crossbites—pressure environment. Skeletal problems Mostly attributed to inherited or genetic cause. Examples: i. Retrognathic mandible and maxilla ii. Prognathic mandible iii. Skeletal deep bite. Heredity It has long been attributed as one of the causes of real malocclusion. i. The child inherits conflicting traits from both the parents who have dissimilar genetic material, resulting in abnormalities of dentofacial region. ii. Uncoordinated inheritance of teeth and jaws is a result of racial, ethnic and regional intermixture. This is another reason attributed to genetically determined malocclusions. According to Lundstrom, the human traits influenced by the genes include: Microdontia I. Tooth size Macrodontia Arch length II. Arch dimensions Arch width III. Crowding and spacing—uncoordinated inheritance of arch length and tooth material IV. Abnormalities of tooth shape, e.g. peg laterals (high genetic predisposition) Anodontia V. Abnormalities of tooth number Oligodontia VI. Overjet— believed to be genetically influenced VII. Interarch variations: Discrepancies in Transverse Sagittal Vertical planes Can be inherited VIII. Frenum: Size, position and shape—genetically influenced, e.g. midline diastema. According to Harris and Johnson, a number of craniofacial parameters showed significant genetic influence. Examples: Sella—gnathion Sella—point A Sella—gonion Nasion—anterior nasal spine Articulare—pogonion Bizygomatic width Anterior facial height. As so many traits show a strong genetic pattern, a number of malocclusions can be partly or solely attributed to genetic factors. These genetic traits can be further influenced by existing prenatal and postnatal environmental factors. SHORT ESSAYS Q. 1. Supernumerary tooth Ans. Teeth that are extra to the normal complement are known as supernumerary teeth. They do not resemble normal teeth and are usually conical in shape. Orthodontics-Part-I-2013.indd 65 They can occur singly or as pair. Mesiodens is the most frequently seen supernumerary tooth. Extra teeth that resemble normal teeth are called supplemental teeth. Example: Most often seen in 245 region. 245 12/3/2013 2:49:14 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 66 Effects of supernumerary and supplemental teeth are as follows: i. These cause non-eruption of adjacent teeth. ii. These deflect erupting adjacent teeth into abnormal location. iii. These can result in crowding and rotation of adjacent teeth. iv. Unerupted mesiodens is one of the causes of midline spacing. v. Unerupted supernumerary teeth are potential risk factors for cystic transformation. Q. 2. Importance of genetics in malocclusion Or Genetic malocclusions Ans. Conditions that are caused due to disturbances in germ plasma or chromosomes or genes are known as genetic disorders. Genetic disorders can be classified into: (i) hereditary and (ii) mutational. The conditions that are transmitted from one generation to another are known as hereditary disorders. According to Lundstrom, the human traits influenced by the genes include: Microdontia I. Tooth size Macrodontia Arch length II. Arch dimensions Arch width III. Crowding and spacing—uncoordinated inheritance of arch length and tooth material IV. Abnormalities of tooth shape, e.g. peg laterals Anodontia V. Abnormalities of tooth number Oligodontia VI. Overjet— believed to be genetically influenced VII. Interarch variations: Discrepancies in Transverse Sagittal Vertical planes can be inherited VIII. Frenum: Size, position and shape—genetically influenced. According to Harris and Johnson, a number of craniofacial parameters showed significant genetic influence. Orthodontics-Part-I-2013.indd 66 Examples: Sella–gnathion, nasion–anterior nasal spine, articulare–pogonion, bizygomatic width, anterior facial height, etc. A number of malocclusions can be partly or solely attributed to genetic factors. These genetic traits can be further influenced by existing prenatal and postnatal environmental factors. Q. 3. Mention local factors in the aetiology of malocclusion. Ans. Various environmental or local factors that cause malocclusion are as follows: A. Disturbances of dental development i. Anomalies of number ii. Anomalies of tooth size iii. Anomalies of tooth shape iv. Premature loss of deciduous teeth v. Prolonged retention of deciduous teeth vi. Delayed eruption of permanent teeth vii. Abnormal eruptive path B. Trauma to the teeth C. Mucosal barriers D. Dental caries E. Improper dental restoration. A. Disturbances of dental development i. Anomalies in number of teeth Teeth that are extra to the normal complement are known as supernumerary teeth. They do not resemble normal teeth and are usually conical in shape. For example: mesiodens, paramolars, etc. Extra teeth that resemble normal teeth are called supplemental teeth. For example: most often seen in 245 245 region. Congenitally missing teeth are far more common than supernumerary teeth. For example: third molars, maxillary lateral incisors, etc. ii. Anomalies of tooth size Increase in size of teeth—macrodontia—results in crowding, e.g. fusion between two adjacent teeth and also between normal tooth and supernumerary tooth. Smaller-sized teeth, i.e. microdontia, results in spacing 2 2 . iii. Anomalies of tooth shape Anomalies of tooth size and shape are interrelated; frequently seen tooth shape anomalies are peg shape 2 2 . Developmental defects like amelogenesis imperfecta, hypoplasia of teeth, fusion and gemination causes anomalies of shape. iv. Premature loss of deciduous teeth It refers to loss of a tooth before its permanent successor is sufficiently advanced in development and eruption to occupy its place. 12/3/2013 2:49:14 PM
  • Topic wise Solved Questions of Previous Years 67 v. Prolonged retention of deciduous teeth Prolonged retention of deciduous teeth Thick mucosal tissue covering erupting teeth acts as a barrier to path of eruption and results in soft tissue impaction. D. Dental caries Anteriors Result in Lingual or palatal eruption of their permanent successors Buccal teeth Dental caries Result in Premature loss of deciduous/permanent teeth Causes Eruption of permanent teeth either buccally or lingually, or may remain impacted Migration of contiguous teeth vi. Delayed eruption of permanent teeth Delayed eruption of permanent teeth may be caused due to congenital absence of permanent tooth, supernumerary tooth blocking eruption of permanent tooth, endocrinal disorders like hypothyroidism, etc. vii. Abnormal eruptive path The abnormal path of eruption may be because of arch length deficiency, presence of supernumerary teeth or retained root fragments, etc. B. Trauma to the teeth Trauma to primary teeth may cause displacement of permanent teeth, defective enamel formation or dilacerated roots. Trauma to permanent teeth may result in ankylosis, nonvitality and displacement of tooth. C. Mucosal barriers Abnormal labial frenum attachments are quite often associated with a maxillary midline spacing. Abnormal axial inclination and supraeruption of opposing teeth E. Improper dental restoration Occlusal restoration: Overcontoured restoration leads to premature contacts and functional shift of man-dible during jaw closure while under contoured restoration permits supraeruption of opposing dentition. Proximal restoration: Undercontoured restoration leads to loss of arch length and food lodgement while overcontoured restorations consume more space leading to irregularity of dentition. Q. 4. Graber’s classification of aetiological factors in malocclusion Ans. Graber’s Classification of Malocclusion General factors 1. Heredity 2. Congenital 3. Environmental a. Prenatal (trauma, maternal diet and metabolism, German measles) b. Postnatal (birth injury, cerebral palsy, TMJ injury) 4. Predisposing metabolic and climatic diseases a. Endocrine imbalance b. Metabolic disturbances c. Infectious diseases 5. Dietary problems (nutritional deficiency) 6. Abnormal pressure habits and functional aberrations a. Abnormal sucking b. Thumb/finger sucking c. Tongue thrust/tongue sucking d. Lip and nail biting e. Abnormal swallowing habits (improper deglutition) f. Speech defects g. Respiratory abnormalities (mouth breathing) h. Tonsils and adenoids i. Psychogenicities and bruxism 7. Posture 8. Trauma and accidents Orthodontics-Part-I-2013.indd 67 Local factors Supernumerary teeth 1. Anomalies of number Missing teeth (congenital absence of loss due to accidents, caries, etc.) 2. Anomalies of tooth size 3. Anomalies of tooth shape 4. Abnormal labial frenum: mucosal barriers 5. Premature loss of deciduous teeth 6. Prolonged retention of teeth 7. Delayed eruption path 8. Abnormal eruptive path 9. Ankylosis 10. Dental caries 11. Improper dental restoration 12/3/2013 2:49:14 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 68 Q. 5. Enumerate the prenatal causes of malocclusion. Ans. The various prenatal causes of malocclusion are as follows: The fetus is well-protected against injuries and nutritional deficiencies during pregnancy; but certain factors can result in abnormal growth of the orofacial region thereby predisposing to malocclusion. Abnormal fetal posture during gestation is said to interfere with symmetric development of the face. Most of these deformities are temporary and usually disappear as age advances. The other prenatal influences include maternal fibroids, amniotic lesions, maternal diet and metabolism. Maternal infection such as German measles and use of certain drugs during pregnancy, such as Thalidomide, can cause gross congenital deformities including clefts. Canine is the least variable tooth in the arch. Butler’s field theory does not apply in lower anterior region, where mandibular central incisor is more commonly missing than lateral incisor. Q. 7. Teratogens Ans. Chemical or other agents that cross the placental barrier and produce embryologic defects are called teratogens. The various teratogens and their effects are as follows: The human dentition is divided into four fields: (i) incisor, (ii) canine, (iii) premolar and (iv) molar regions. The most distal tooth in each field is the most susceptible to changes or variations like absence of tooth and variation in size, shape and structure. Accordingly, lateral incisors, second premolars and third molars are the most variable teeth in their group. This is called Butler’s field theory. i. Aspirin, cigarette smoke, dilantin and valium Cleft lip and palate ii. 6-Mercaptopurine Cleft palate iii. Aminopterin Anencephaly Microcephaly, hydrocephaly v. Ethyl alcohol Ans. Effect iv. Cytomegalovirus Q. 6. Butler’s field theory Teratogens Central midface deficiency vi. 13-cis-retinoic acid Retinoic acid syndrome vii. Rubella virus Microphthalmia, deafness viii. Thalidomide Hemifacial microsomia like features ix. Toxoplasma Microcephaly, hydrocephaly x. Radiation Microcephaly xi. Vitamin D excess Premature suture closure SHORT NOTES Q. 1. Ankylosis Ans. Ankylosis is a condition wherein a part or whole of the root surface is directly fused to the bone with the absence of the intervening periodontal membrane. It occurs most often as a result of trauma to the tooth that perforates the periodontal membrane. It can also be associated with certain infections, endocrinal disorders and congenital disorders like cleidocranial dysostosis. Clinically, these teeth fail to erupt to the normal level and are therefore called submerged teeth. Q. 2. General factors causing malocclusion Ans. General factors causing malocclusion are as follows: i. Heredity Orthodontics-Part-I-2013.indd 68 ii. iii. iv. v. Congenital Predisposing metabolic and climatic diseases Dietary problems (nutritional deficiency) Abnormal pressure habits and functional aberrations, e.g. thumb/finger sucking, tongue thrust, nail biting, etc. vi. Posture vii. Trauma and accidents. Q. 3. Prenatal causes for malocclusion Ans. The various prenatal causes of malocclusion are as follows: Abnormal fetal posture during gestation interferes with symmetric development of the face. Prenatal influences include maternal fibroids, amniotic lesions, maternal diet and metabolism. Maternal infections, e.g. German measles. 12/3/2013 2:49:14 PM
  • Topic wise Solved Questions of Previous Years 69 Use of certain drugs during pregnancy such as Thalidomide can cause gross congenital deformities, including clefts. Q. 4. Local factors causing malocclusion Or Mention local factors in aetiology of malocclusion. Ans. Various environmental or local factors that cause malocclusion are as follows: i. Disturbances of dental development a. Anomalies of number, tooth size and shape b. Premature loss of deciduous teeth c. Prolonged retention of deciduous teeth d. Delayed eruption of permanent teeth e. Abnormal eruptive path ii. Trauma to the teeth iii. Mucosal barriers: Abnormal labial frenum attachment and soft tissue impaction iv. Dental caries v. Improper dental restorations. Q. 5. Teratogens Ans. Chemical or other agents that cross the placental barrier and produce embryologic defects are called teratogens. Examples of various teratogens and their effects are as follows: Teratogens Effect i. Aspirin, cigarette smoke, dilantin and valium Cleft lip and palate ii. 6-Mercaptopurine Cleft palate iii. Cytomegalovirus Microcephaly, hydrocephaly iv. Ethyl alcohol Central midface deficiency v. Radiation Microcephaly vi. Vitamin D excess Premature suture closure Q. 6. Supernumerary teeth Ans. Teeth that are extra to the normal complement are known as supernumerary teeth. They do not resemble normal teeth and are usually conical in shape. They can occur singly or as pair, e.g. mesiodens, paramolars, etc. Mesiodens is most frequently seen in supernumerary teeth. Orthodontics-Part-I-2013.indd 69 Q. 7. Dilacerated teeth Ans. Dilaceration is described as a condition characterized by an abnormal angulation between the crown and root of a tooth or angulation within the root. It usually occurs due to trauma to a deciduous tooth, which is transmitted to the underlying permanent tooth bud. Dilacerated teeth fail to erupt to normal level and can thus cause malocclusion. Q. 8. Submerged teeth Ans. Clinically, ankylosed teeth fail to erupt to the normal level and are therefore called submerged teeth. At times, these teeth are totally submerged within the jaw and therefore cause migration of adjacent teeth into the space. Q. 9. Supplemental teeth Ans. Extra teeth that resemble normal teeth are called supplemental teeth. For example: most often seen in 245 245 region. Effects of supernumerary and supplemental teeth are as follows: i. They cause non-eruption of adjacent teeth. ii. They deflect erupting adjacent teeth into abnormal location. iii. They can result in crowding and rotation of adjacent teeth. iv. Unerupted mesiodens is one of the causes of midline spacing. v. Unerupted supernumerary teeth are potential risk factors for cystic transformation. Q. 10. Genetic malocclusions Ans. Conditions that are caused due to disturbances in germ plasma or chromosomes or genes are known as genetic disorders. Genetic disorders can be classified as: (i) hereditary and (ii) mutational. According to Lundstrom, the human traits influenced by the genes include: i. Tooth size like microdontia and macrodontia. ii. Arch dimensions, i.e. arch length and arch width iii. Abnormalities of tooth shape, e.g. peg laterals. Crowding and spacing because of uncoordinated inheritance of arch length and tooth material. 12/3/2013 2:49:14 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 70 Q. 11. Enlist the causes of midline diastema. Ans. Midline diastema is a form of localized spacing, where a spacing is present between two central incisors. It occurs due to following causes: i. Normal developmental causes a. Physiologic median diastema b. Ethnic and familial ii. Tooth material deficiency a. Microdontia b. Missing lateral and peg lateral iii. Physical impediment a. Retained deciduous teeth b. Mesiodens iv. Habits: Thumb sucking, tongue thrusting, etc. Dental caries can lead to premature loss of deciduous or permanent teeth, thereby causing migration of contiguous teeth, abnormal axial inclination and supraeruption of opposing teeth. Q. 14. Aetiology of crowding Ans. Crowding and spacing of teeth are believed to be of genetic origin. Most of these conditions are believed to be a result of uncoordinated inheritance of arch length and tooth material. Arch length–tooth material discrepancy leads to crowding. Q. 15. Prolonged retention of deciduous teeth Q. 12. Acromegaly Ans. Ans. Hyperpituitarism results in gigantism and acromegaly. Acromegaly is due to hypersecretion of GH in adults. Gigantism is due to hypersecretion of GH in childhood before fusion of epiphysis of bone with shaft. Gigantism is characterized by a general symmetric overgrowth of the body. Skeletal changes include enlarged supraorbital ridges and prognathic mandible, enlargement of the tongue and whole face. Patients may develop class III malocclusion with interdental spacing. Mandibular prognathism, labial or buccally tilted teeth and enlarged tongue are the features of acromegaly. Prolonged retention of deciduous teeth Anteriors Result in Lingual or palatal eruption of their permanent successors Q. 13. How does dental caries causes malocclusion? Buccal teeth Result in Eruption of permanent teeth either buccally or lingually or may remain impacted Ans. Dental caries causes malocclusion by the following consequences: Dental caries Premature loss of deciduous/permanent teeth Causes Migration of contiguous teeth Abnormal axial inclination and supraeruption of opposing teeth Orthodontics-Part-I-2013.indd 70 Q. 16. Blanch test Ans. High frenum attachment condition is diagnosed by a positive blanch test. A heavy fibrous frenum is found attached to the interdental papilla region. This type of frenum attachment can prevent the two maxillary central incisors from approximating each other, leading to midline diastema. Procedure: When the upper lip is stretched for a period of time, a noticeable blanching occurs over the interdental papilla. A midline, intraoral periapical radiograph usually exhibits notching of the interdental alveolar crest. 12/3/2013 2:49:14 PM
  • Topic wise Solved Questions of Previous Years 71 Topic 9 ORAL HABITS LONG ESSAYS Q. 1. Define habits. Classify and discuss in detail about the features of tongue thrusting habit and its treatment modalities. Or Classify tongue thrusting habit. Discuss its aetiology, clinical features and management. Ans. Habit can be defined as the tendency towards an act that has become a repeated performance, relatively fixed, consistent and easy to perform by an individual. Tongue thrusting is defined as a condition in which the tongue makes contact with any teeth anterior to the molars during swallowing. This deleterious habit clinically presents with open bite and anterior proclination. Aetiology The factors considered as cause of tongue thrusting habit according to Fletcher are as follows: i. Genetic factors ii. Learned behaviour (habit) iii. Maturational factors iv. Mechanical restrictions v. Neurological disturbance vi. Psychogenic factors. i. Genetic factors: Specific anatomic or neuromuscular variations in orofacial region can precipitate tongue thrust, e.g. hypertonic orbicularis oris activity. ii. Learned behaviour (habit): Tongue thrusting can be acquired as a habit due to following predisposing factors: a. Improper bottle feeding b. Prolonged thumb sucking c. Prolonged tonsillar or upper respiratory tract infections d. Prolonged duration of tenderness of gums or teeth tends to change the swallowing pattern. iii. Maturational factors: a. Macroglossia b. Constricted dental arches c. Enlarged adenoids and tonsils. These cause tongue to be positioned anteriorly to prevent blocking of the oropharynx. Orthodontics-Part-I-2013.indd 71 iv. Neurological disturbance of orofacial region can cause tongue thrust habit, e.g. hyposensitive palate and moderate motor disability. v. Psychogenic factors: Tongue thrusting habit may develop as a result of forced discontinuation of other habits like thumb sucking. Classification of Tongue Thrusting Habit According to James S Braner and Holt tongue thrusting habit can be classified as follows: Type I: Non-deforming tongue thrust Type II: Deforming anterior tongue thrust i. Anterior open bite ii. Anterior proclination 3 Subgroups iii. Posterior crossbite Type III: Deforming lateral tongue thrust i. Posterior open bite ii. Posterior crossbite 3 Subgroups iii. Deep overbite Type IV: Deforming anterior and lateral tongue thrust i. Anterior and posterior open bite ii. Proclination of anterior teeth 3 Subgroups iii. Posterior crossbite Moyers classified tongue thrusting into three types: i. Simple tongue thrusting: Characterized by teeth together swallow. ii. Complex thrusting: Characterized by teeth apart swallow. iii. Retained infantile swallow. Clinical Features The clinical features seen in tongue thrusting condition are dependent on type of tongue thrusting. Some common clinical features of tongue thrust habit are as follows: i. Proclination of anterior teeth ii. Bimaxillary protrusion iii. Anterior open bite and iv. In case of lateral tongue thrust posterior open bite and posterior crossbite. i. Simple tongue thrust habit It is also called teeth together swallow. There is normal tooth contact during swallowing. 12/3/2013 2:49:14 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 72 Generalized spacing and proclination may be seen in the upper and lower anterior teeth. Increased overjet, reduced overbite or presence of anterior open bite may be seen. Tongue is thrust forward during swallowing to help in establishing anterior lip seal. Exaggerated perioral musculature during the swallowing action. Especially hyperactive mentalis muscle activity is seen. ii. Complex tongue thrust habit It is defined as tongue thrust with teeth apart swallow. There are two important diagnostic features: (i) generalized open bite and (ii) poor occlusal fit of teeth, which leads to sliding occlusion. Absence of temporal muscle constriction during swallowing and the mandible is not stabilized by the elevator muscles. iii. Retained infantile swallow Little is known about the exact aetiology of this severe problem. Treatment Interception and treatment of tongue thrusting is age and severity dependent. In children below 3 years, no active intervention is instituted, whereas children above this age can be trained for tongue swallowing exercises. The various modalities of treatment of tongue thrusting are as follows: i. Reminder therapy/interception of habit ii. Corrective therapy. i. Reminder therapy/interception of habit Use of habit breakers—both fixed and removable cribs and rakes. Some of the commonly used removable appliances include upper Hawley’s plate with tongue cribs, roller balls for tongue exercise. Teaching correct method of swallowing to the child. ii. Corrective therapy a. b. c. d. e. Removal of obstruction Tongue exercises Lip exercises Habit-breaking appliance Treatment of malocclusion. a. Removal of obstruction Surgery for adenoids and macroglossia Closure of anterior and posterior open bites, anterior spaces with either fixed or removable orthodontic appliance. Orthodontics-Part-I-2013.indd 72 b. Tongue exercises Various muscle exercises of tongue to adapt it to new swallowing pattern with removable or fixed orthodontic appliances is advised after habit is intercepted; they are as follows: Tongue exercises include: i. Elastic band swallow exercise: Small orthodontic elastic band is held up the tongue tip against the palate during swallowing and asked to practice. If the swallow is correct, patient will be able to hold the elastic; otherwise it will fall or will be swallowed. ii. Water swallow exercise: Patient is advised to keep water in mouth and a mirror in the hand and swallowing is practised daily. iii. Candy swallow exercise: A flat, sugarless candy is placed between tongue and palate and swallowing is practised. This exercise reinforces the learned new swallowing pattern to be transferred to the subconscious level. iv. Speech exercise: Patient practices syllables like ‘c’, ‘g’, ‘h’ and ‘k’ while keeping an elastic band between the tongue and the palate. c. Lip exercises Patient practices stretching of lips so as to achieve anterior lip seal. d. Habit-breaking appliance i. The tongue-thrusting appliance has fixed tongue spikes fabricated with 0.040 inch stainless steel alloy. It is Vshaped with three or four projections, which extend up to cingulum of lower incisors soldered to molar bands or crowns. It acts as a picket fence preventing or limiting the tongue. ii. The optimum age to use this appliance is 5–10 years. iii. A modified tongue crib is used in the patients with lateral tongue-thrusting habit. e. Treatment of malocclusion Malocclusion is treated with either removable or fixed orthodontic appliances. Q. 2. Enumerate the aetiological factors causing mouth breathing in children and discuss the line of treatment. Or Define abnormal pressure habits. Write in detail about the classification, clinical findings and treatment for mouth breathers. Or Mouth-breathing habit and its effects on the development of occlusion. 12/3/2013 2:49:14 PM
  • Topic wise Solved Questions of Previous Years 73 Ans. Clinical Features i. Mouth breathing is an altered way of breathing through mouth and an adaptation to obstruction in nasal passages. The obstruction may be temporary or recurrent. Although more often it is partial than complete, the airway resistance may be enough to force the subject to breathe through the mouth. ii. Mouth breathing is usually attributed as an aetiological factor for malocclusion. iii. Mouth breathing results in altered jaw and tongue posture, which in turn alters orofacial equilibrium leading to malocclusion. i. The type of malocclusion associated with mouth breathing is called long face syndrome or classic adenoid facies or vertical maxillary excess. ii. Long and narrow face with short and flaccid upper lip. iii. Expressionless, blank face. iv. Anterior open bite. v. Contraction of upper arch, narrow V-shaped upper jaw with a high narrow palate, posterior crossbite. vi. ↑ Overjet due to flaring of maxillary anteriors. vii. Anterior marginal gingivitis and ↑ caries incidence. viii. Narrow nose and nasal passage, widely flared external nares. ix. Excessive appearance of maxillary anterior teeth with a ‘gummy smile’. Classification of Mouth Breathers Mouth breathers are of three types Diagnosis Obstructive Habitual Anatomic Complete or partial obstruction of nasal passage results in mouth breathing Due to deep-rooted habit that is unconsciously performed Patients with short upper lip that does not permit complete mouth closure Aetiology Obstructive causes Nasal polyps Obstructive adenoids Congenital enlargement of nasal turbinates Chronic inflammation of nasal mucosa Benign tumours Deviated nasal septum. Diagnosis is based on the following: i. History of the patient ii. Clinical examination iii. Some simple tests a. Mirror condensation test b. Water holding test c. Cotton wisp test. iv. Cephalometrics: It helps to assess the amount of nasopharyngeal space, size of adenoids and diagnosing long face. v. Rhinomanometry a. Study of nasal airflow characteristics using devices like flow meter and pressure gauges. b. Estimation of airflow through nasal passage and amount of nasal resistance. Treatment Anatomic causes Removal of nasal or pharyngeal obstruction by ENT surgeon. Interception of the habit—vestibular screen adhesive tapes for lip seal. Rapid maxillary expansion—causes widening of arch, resulting in ↑ nasal flow and ↓ nasal air resistance. Short upper lip Underdeveloped nasal cavity. Obstructive sleep apnoea Pathophysiology of mouth breathing Oral respiration 3 changes in posture Q. 3. Define and classify habits. Discuss clinical pictures and management of thumb-sucking habit. Or Lowering of mandible Position of tongue (downward and forward) Upset orofacial equilibrium, unrestricted buccinator activity influences position of teeth and growth of jaws Orthodontics-Part-I-2013.indd 73 Tipping back of head Describe various oral habits directly responsible for causing malocclusion. Discuss management of one such habit in detail. Or Define a habit. How do you classify habits? Discuss the aetiology, effects and management of thumb sucking. 12/3/2013 2:49:15 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 74 According to Klein Or Define preventive and interceptive orthodontics. Discuss the management of thumb-sucking habit. Ans. HABITS Habit can be defined as the tendency towards an act that has become a repeated performance, relatively fixed, consistent and easy to perform by an individual. Meaningful habits Habits not associated with any deep-rooted psychological problems. For example: • Abnormal pillowing • Chin propping. Habits that have a psychological bearing. For example: • Nail biting • Lip biting • Digit sucking. According to Finn Compulsive habits Classification According to different authors habits have been classified as follows: Author Classification Useful habits James (1923) Harmful habits Pressure habits Morris and Bohanna (1969) Non-compulsive habits i. These are deep-rooted habits i. These include habits that are that have acquired a fixation in easily learned and the child to the extent that the dropped as the child matures. child retreats to the habit whenever his/her security is threatened by events that occur around him/her. ii. The child tends to suffer increased anxiety when an attempt is made to correct the habits. Non-pressure habits Biting habits THUMB SUCKING Empty habits Klein (1971) Digit sucking or thumb sucking is defined as the placement of the thumb or one or more fingers in varying depths into the mouth. Meaningful habits Compulsive habits Finn (1987) Non-compulsive habits According to James Useful habits Harmful habits The habits that are essential for The habits that have deleterious normal function effect on the teeth and their supporting structures For example: • Proper positioning of tongue • Respiration • Normal deglutition. For example: • Thumb sucking • Tongue thrusting, etc. According to Morris and Bohanna Pressure habits Non-pressure habits Biting habits Include sucking habits such as: • Thumb sucking • Lip sucking • Finger sucking • Tongue thrusting. Include habits that do not apply direct force on a teeth or their supporting structures such as: • Mouth breathing Include various biting habits such as: • Nail biting • Pencil biting • Lip biting. Orthodontics-Part-I-2013.indd 74 Empty habits Aetiology Causative factors include: i. Parent’s occupation: Low socioeconomic groups are more prone to thumb sucking. ii. Working mother: Children with insecurity feeling cultivate the habit. iii. Number of siblings: More the number of children, neglecting of child leads to development of this habit. iv. Order of birth of child: Later the sibling rank of a child, greater are the chances of oral habit. v. Social adjustment and stress vi. Feeding practices vii. Age of the child. Some of the more commonly accepted theories to explain the thumb-sucking habit are as follows: i. Freudian theory ii. Benjamin’s theory iii. Psychological aspects iv. Oral drive theory v. Learned pattern theory. i. Freudian theory (1905): Proposed by Sigmond Freud. He suggested that a child passes through various phases of psychological development, of which oral and anal phases are seen in first 3 years of life. 12/3/2013 2:49:15 PM
  • Topic wise Solved Questions of Previous Years 75 In oral phase → Mouth is believed to be oro-erotic zone ↓ The child has tendency to place his fingers or any object into the oral cavity ↓ Prevention of such habit is believed to result in emotional insecurity and poses risk of child diversifying into other habits ii. Benjamin’s theory: Suggests that thumb sucking arises from rooting or placing reflex seen in all mammalian infants. iii. Psychological aspects: Feeling of insecurity in children deprived of parental love and affection are believed to resort to this habit. iv. Oral drive theory (1950): Proposed by Sears and Wise (1982) stated that prolonged sucking can lead to thumb sucking. Phases of Development of Thumb Sucking Phase I Phase II Phase III Normal and subclinically significant Clinical significant sucking Intractable sucking Seen during first 3 years of life and is considered quite normal Seen during 3–6½ years of age group Persistent beyond 4th or 5th year of life No treatment required, usually terminates at the end of phase I Treatment: Dental problems should be solved in this phase Treatment: Consultation with a psychologist is required in this phase iii. Anterior open bite (↓ overbite)—restriction of incisor eruption and supraeruption of buccal teeth. iv. Posterior crossbite—narrow maxillary arch predisposing to crossbite due to contraction of cheek muscles during thumb sucking. v. Tongue thrust—develops as a result of open bite. vi. Effects on lip—hypotonic upper lip, hyperactive lower lip, ↑ lip incompetence, hyperactive mentalis activity. vii. Other effects are—psychological health, risk of malposition of jaws, speech defects, digit defects. Diagnosis i. History—frequency and duration of habit. ii. Child’s emotional status—assessed by enquiring Feeding habits Parental care of child Working parents. iii. Examination of child’s fingers—presence of clean nails and callus on finger. iv. Intraoral clinical examination—proclination, open bite, etc. Treatment The child, parent and dentist form a team to assist the child in stopping the habit. Treatment is mainly of three categories: i. Psychological therapy ii. Reminder therapy or mechanotherapy—removable habit breakers and fixed habit breakers iii. Chemical approach. i. Psychological treatment Clinical Effects of Thumb Sucking Dentofacial changes associated with thumb sucking can affect maxilla, mandible, interarch relationship, lip placement and function, etc. The severity of malocclusion caused by thumb sucking depends on the following factors: i. Duration: Amount of time spent in indulging in the habit. ii. Frequency: Number of times habit activated/day. iii. Intensity: Vigour with which the habit is performed. The effects of thumb sucking on dental arch and its supporting structures are as follows: i. Proclination or labial tipping of maxillary anterior teeth. ii. Increasing overjet—due to proclination of maxillary anterior and lingual tipping of mandibular incisors. Orthodontics-Part-I-2013.indd 75 a. Screening patients for underlying psychological disturbances and referring to professionals for counselling. b. Children between 4 and 8 years of age need only reassurance, positive reinforcement and friendly reminders to divert the child’s attention to other things like play and toys. c. Dunlop’s beta hypothesis Forced purposeful repetition of a habit eventually associated with unpleasant reactions and habit is abandoned. Dunlop’s beta hypothesis is especially practised in older children, i.e. 8 years and above. ii. Reminder therapy or mechanical aids These are basically reminding appliances that assist to quit the habit. 12/3/2013 2:49:15 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 76 There are two types of habit breakers as follows: Removable Fixed i. These are passive and removable appliances consisting of a crib placed palatal to 21 12 and anchored to oral cavity by means of clasps on posterior teeth. Examples: • Tongue spikes (Fig. 9.1) • Tongue guard (Fig. 9.2) • Spurs/rake. i. This appliance (Fig. 9.3) consists of molar bands/crowns on first permanent molars with palatal assembly and soldered spurs made of either nickel–chrome or stainless steel. Examples: • Quad helix • Hay rakes • Maxillary lingual arch with palatal crib ii. The best appliance is a heavy gauge stainless steel wire designed to form a frame that is soldered to molar bands. Other mechanical aids used to intercept the habit include: Bandaging of the thumb Bandaging of the elbow. iii. Chemical approach Use of bitter-tasting or foul-smelling preparations placed on thumb that is sucked can make the habit distasteful. Commonly used medicaments are: a. Pepper dissolved in a volatile medium b. Quinine c. Asafoetida. Q. 4. Describe how tongue thrust, mouth breathing and thumb-sucking habits cause malocclusion. Ans. Habit can be defined as the tendency towards an act that has become a repeated performance, relatively fixed, consistent and easy to perform by an individual. Due to their repetitive nature and longer duration, the orofacial habits influence the form of orofacial structures. The pathophysiology of various habits causing malocclusion is as follows: i. Tongue-thrusting habit Fig. 9.1 Tongue spike. The repeated anterior positioning of the tongue leads to anterior open bite, protruded and spaced anterior teeth, and an incompetent anterior lip seal; all of these effects lead to tongue thrusting-like situation. ii. Mouth breathing A child suffering from nasorespiratory blockage due to any reason like enlarged tonsils, recurrent throat infections, etc. tends to keep the tongue low and forward, and is unable to maintain anterior lip seal. Such patients develop a mouth-breathing habit with consequent mouth open posture. These children develop a long face known as adenoid facies. Fig. 9.2 Tongue guard. Fig. 9.3 Fixed habit breaker. Orthodontics-Part-I-2013.indd 76 iii. Sucking habits Development of normal orofacial function is greatly hindered by continuation of non-nutritive sucking habits beyond 4–5 years of age. During thumb or finger sucking mouth remains open and the tongue is positioned forward and low in the mouth; because of this an abnormal pressure is generated by contraction of cheek muscles, resulting in an imbalance in intraoral force system. Exaggerated buccinator activity during sucking and swallowing results in constricted maxilla, buccal crossbite, lowered and backward mandibular posture resulting in class II division 1 malocclusion. 12/3/2013 2:49:15 PM
  • Topic wise Solved Questions of Previous Years 77 SHORT ESSAYS Q. 1. Thumb-sucking habit Ans. Thumb sucking is defined as the placement of thumb or one or more fingers in varying depths into the mouth. Theories involved in explaining thumb-sucking habit are: i. Freudian theory ii. Oral drive theory iii. Benjamin’s theory iv. Psychological aspects v. Learned pattern theory Phases of development of thumb sucking i. Phase I: Normal, seen during first 3 years of life ii. Phase II: Clinically significant, 3–6½ years iii. Phase III: Intractable sucking, beyond 4th or 5th year of life. Clinical features i. Proclination of maxillary anteriors ii. ↑ overjet and ↓ overbite iii. Anterior open bite and posterior crossbite iv. Tongue thrust, hypotonic upper lip and hyperactive mentalis muscle. Diagnosis It is based on i. History of habit ii. Child’s emotional status iii. Examination of the child’s fingers—clean nails and callus on finger iv. Intraoral clinical examination. Treatment i. Psychological therapy ii. Mechanical aids: a. Removable b. Fixed habit breakers c. Chemical approach. i. Psychological therapy Counselling of parents to provide adequate love and affection to the child. Advice parents to divert the child’s attention to other things like play and toys. ii. Mechanical aids Habit-breaking appliances i. Removable a. Tongue spikes b. Tongue guard. Orthodontics-Part-I-2013.indd 77 ii. Fixed a. Quad helix b. Hay rakes. Other mechanical aids used to intercept the habit are bandaging of thumb and elbow. iii. Chemical approach: Chemical approach of treatment is by using bitter-tasting and foul-smelling chemicals placed on thumb, e.g. pepper dissolved in a volatile medium, quinine, asafetida. Q. 2. Mouth-breathing habit Or Mouth-breathing habit and its effects on the development of occlusion Ans. Mouth breathing is an altered way of breathing through mouth and an adaptation to obstruction in nasal passages. The obstruction may be temporary or recurrent. While more often it is partial than complete. Mouth breathing results in altered jaw and tongue posture, which in turn alters orofacial equilibrium leading to malocclusion. Mouth breathers are classified into: i. Obstructive ii. Habitual iii. Anatomic. Aetiology i. Obstructive causes Nasal polyps Obstructive adenoids Congenital enlargement of nasal turbinates Chronic inflammation of nasal mucosa Benign tumours Deviated nasal septum. ii. Anatomic causes Short upper lip Underdeveloped nasal cavity. iii. Obstructive sleep apnoea. Clinical features The type of malocclusion associated with mouth breathing is called long face syndrome or classic adenoid facies or vertical maxillary excess. 12/3/2013 2:49:15 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 78 Long and narrow expressionless, blank face with short and flaccid upper lip. Anterior open bite. Narrow V-shaped upper jaw with a high narrow palate, posterior crossbite. ↑ overjet due to flaring of maxillary anteriors. Anterior marginal gingivitis and ↑ caries incidence. Narrow nose and nasal passage. Diagnosis Diagnosis is based on the following: History and clinical examination of the patient Some simple tests like mirror condensation test , water holding test and cotton wisp test Cephalometrics Rhinomanometry. Treatment Removal of nasal or pharyngeal obstruction by ENT surgeon. Interception of the habit—vestibular screen adhesive tapes for lip seal. Rapid maxillary expansion—causes widening of arch, resulting in ↑ nasal flow and ↓ nasal air resistance. Q. 3. Classify tongue-thrusting habit. Add a note on its management. Or Write briefly about tongue-thrusting habit. Ans. Tongue thrusting is defined as a condition in which the tongue makes contact with any teeth anterior to the molars during swallowing. Aetiology The factors considered as a cause of tongue thrusting habit according to Fletcher are as follows: ❍ Genetic factors, e.g. hypertonic orbicularis oris activity ❍ Learned behaviour (habit): due to improper bottle feeding, prolonged thumb sucking, prolonged tonsillar or upper respiratory tract infections, etc. ❍ Maturational factors, e.g. macroglossia, constricted dental arches, and enlarged adenoids and tonsils, etc. ❍ Mechanical restrictions ❍ Neurological disturbance, e.g. hyposensitive palate and moderate motor disability ❍ Psychogenic factors. Classification of tongue-thrusting habit i. According to James S Braner and Holt Type I: Non-deforming tongue thrust Type II: Deforming anterior tongue thrust Orthodontics-Part-I-2013.indd 78 i. Anterior open bite ii. Anterior proclination 3 subgroups iii. Posterior crossbite. Type III: Deforming lateral tongue thrust i. Posterior open bite ii. Posterior crossbite 3 subgroups iii. Deep overbite. Type IV: Deforming anterior and lateral tongue thrust i. Anterior and posterior open bite ii. Proclination of anterior teeth 3 subgroups iii. Posterior crossbite. ii. Moyers classified tongue thrusting into three types i. Simple tongue thrusting: Characterized by teeth together swallow ii. Complex thrusting: Characterized by teeth apart swallow iii. Retained infantile swallow. Clinical Features The clinical features seen in tongue-thrusting condition are dependent on type of tongue thrusting. Some common clinical features of tongue-thrusting habit are as follows: i. Proclination of anterior teeth ii. Bimaxillary protrusion iii. Anterior open bite iv. In case of lateral tongue thrust, posterior open bite and posterior crossbite. Treatment Interception and treatment of tongue thrusting is age and severity dependent. In children below the age of 3 years, no active intervention is instituted whereas children above this age can be trained for tongue swallowing exercises. The various modalities of treatment of tongue thrusting are as follows: i. Reminder therapy/interception of habit ii. Corrective therapy. i. Reminder therapy/interception of habit Use of habit breakers both fixed and removable cribs and rakes. Some of the commonly used removable appliances include upper Hawley’s plate with tongue cribs, roller balls for tongue exercise. Teaching correct method of swallowing to child. ii. Corrective therapy Removal of obstruction: Surgery for adenoids and macroglossia Tongue exercises i. Elastic band swallow exercise ii. Water swallow exercise iii. Candy swallow exercise iv. Speech exercise 12/3/2013 2:49:15 PM
  • Topic wise Solved Questions of Previous Years 79 Lip exercises: Patient practices stretching of lips so as to achieve anterior lip seal. Habit-breaking appliance, e.g. tongue crib. Treatment of malocclusion: Either removable or fixed orthodontic appliances. Q. 4. Bruxism Ans. Grinding of teeth for non-functional purposes is known as bruxism. Types There are two types of bruxism. i. Nocturnal grinding—Bruxism ii. Day grinding—Bruxomania. Aetiology Psychological and emotional stresses Occlusal interference or discrepancy between CR (centric relation) and CO (centric occlusion) Pericoronitis and periodontal pain triggers bruxism. Clinical features Occlusal wear facets on teeth Mobility of teeth Fractured teeth and restorations Muscle pain—on waking up in the morning TMJ pain and discomfort Tenderness and hypertrophy of masticatory muscles. Diagnosis History and clinical examination are helpful in diagnosis of bruxism. Check for occlusal prematurities using articulating paper. Check for hyperactivity of muscles of mastication, i.e. electromyography examination. Treatment Psychological counselling Relieving muscle tension by: ❍ Hypnosis ❍ Relaxing exercises ❍ Massage. Occlusal adjustments Night guards or occlusal splints. SHORT NOTES Q. 1. Mouth breathing Or Role of mouth breathing in aetiology of malocclusion Ans. Mouth breathing is an altered way of breathing through mouth and an adaptation to obstruction in nasal passages. Mouth breathing results in altered jaw and tongue posture, which in turn alters orofacial equilibrium leading to malocclusion. The type of malocclusion associated with mouth breathing is called long face syndrome or classic adenoid facies or vertical maxillary excess. Clinical features: Anterior open bite and posterior crossbite, narrow V-shaped upper jaw with a high narrow palate, short and flaccid upper lip. Treatment of mouth breathing includes removal of nasal or pharyngeal obstruction by ENT surgeon, interception of the habit using vestibular screen adhesive tapes for lip seal and rapid maxillary expansion. Orthodontics-Part-I-2013.indd 79 Q. 2. Thumb-sucking habit Ans. Thumb sucking is defined as the placement of thumb or one or more fingers in varying depths into the mouth. Clinical features: Proclination of maxillary anteriors,↑ overjet and ↓ overbite, anterior open bite and posterior crossbite, tongue thrust, hypotonic upper lip and hyperactive mentalis muscle. It is diagnosed based on history, the child’s emotional status, examination of the child’s fingers, i.e. clean nails and callus on fingers and intraoral clinical examination. Treatment of thumb sucking includes psychological therapy, use of mechanical aids like habit-breaking appliances, e.g. tongue spikes, tongue guard, hay rakes, etc., and chemical approach using bitter-tasting and foul-smelling chemicals placed on the thumb. Q. 3. Lip sucking and lip biting Ans. Lip sucking and lip biting are usually seen in cases of excessive overjet. 12/3/2013 2:49:15 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 80 These involve cushioning of the lower lip against palatal surfaces of maxillary incisors causing them flare forward. Due to indirect pressure delivered to labial surface of mandibular incisors these move lingually, increasing the overjet. Hypertrophied lower lips and associated hyperactive mentalis activity are seen. Lip bumpers are used to treat upper and lower lip problems. These appliances prevent abnormal force acting on the incisors and hyperactivity of mentalis muscle. Q.4. Define tongue-thrusting habit. Or Aetiology of tongue-thrusting Ans. Tongue thrusting is defined as a condition in which the tongue makes contact with any teeth anterior to the molars during swallowing. Aetiology The factors considered as a cause of tongue-thrusting habit according to Fletcher are as follows: Genetic factors, e.g. hypertonic orbicularis oris activity Learned behaviour (habit): due to improper bottle feeding, prolonged thumb sucking, prolonged tonsillar or upper respiratory tract infections, etc. Maturational factors, e.g. macroglossia, constricted dental arches, and enlarged adenoids and tonsils Mechanical restrictions Neurological disturbance, e.g. hyposensitive palate and moderate motor disability. Psychogenic factors. Q. 5. Adenoid facies Ans. The type of malocclusion associated with mouth breathing is called long face syndrome or adenoid facies. The term ‘adenoid facies’ was coined by Tomes in 1872 to describe dentofacial changes associated with chronic nasal airway obstruction. These patients have increase in lower anterior face height associated with unfavourable ‘clockwise’ rotation of the mandible in a more vertical and posterior direction, open bite, crossbite and retrognathia. In growing patients following adenoidectomy and orthodontic treatment, changes would reverse back to normal. Q. 6. Classify tongue-thrusting habit. Ans. Classification of tongue-thrusting habit Orthodontics-Part-I-2013.indd 80 According to James S Braner and Holt Type I: Non-deforming tongue thrust Type II: Deforming anterior tongue thrust i. Anterior open bite ii. Anterior proclination 3 Subgroups iii. Posterior crossbite. Type III: Deforming lateral tongue thrust i. Posterior open bite ii. Posterior crossbite 3 Subgroups iii. Deep overbite. Type IV: Deforming anterior and lateral tongue thrust i. Anterior and posterior open bite ii. Proclination of anterior teeth 3 Subgroups iii. Posterior crossbite. Moyers classified tongue thrusting into three types. i. Simple tongue thrusting: Characterized by teeth together swallow ii. Complex thrusting: Characterized by teeth apart swallow iii. Retained infantile swallow. Q. 7. Write a note on management of tongue-thrusting habit Ans. Management of tongue-thrusting habit: Interception and treatment of tongue thrusting is age and severity dependent. The various modalities of treatment of tongue thrusting are as follows: Reminder therapy/interception of habit Use of habit breakers—both fixed and removable cribs and rakes. Corrective therapy Removal of obstruction: Surgery for adenoids and macroglossia. Tongue exercises i. Elastic band swallow exercise ii. Water swallow exercise iii. Candy swallow exercise iv. Speech exercise. Lip exercises: Patient practices stretching lips so as to achieve anterior lip seal. Habit-breaking appliance, e.g. tongue crib. Treatment of malocclusion: Either removable or fixed orthodontic appliances. Q. 8. Habit-breaking appliances Ans. There are two types of habit-breaking appliances: (i) removable and (ii) fixed. 12/3/2013 2:49:15 PM
  • Topic wise Solved Questions of Previous Years 81 Removable appliances Fixed appliances i. These are passive and removable appliances consisting of a crib placed palatal to 21 12 and anchored to oral cavity by means of clasps on posterior teeth. For example: Tongue spikes, tongue guard, spurs/rake. i. These appliances consist of molar bands/crowns on first permanent molars with palatal assembly and soldered spurs made of either nickel–chrome or stainless steel. For example: Quad helix, hay rakes, maxillary lingual arch with palatal crib. ii. The best appliance is heavy gauge stainless steel wire designed to form a frame that is soldered to molar bands. Psychological therapy: Forced, purposeful repetition of a habit eventually associated with unpleasant reactions and the habit is abandoned. Reminder therapy or mechanical aids: These are habitbreaking appliances that assist to quit the habit and are of two types—removable and fixed. Examples: i. Removable appliances: Tongue spikes, tongue guard, spurs/rake, etc. ii. Fixed appliances: Quad helix, hay rakes and maxillary lingual arch with palatal crib. Chemical approach: Use of bitter-tasting or foul-smelling preparations placed on thumb that is sucked can make the habit distasteful. Q. 9. Lip biting Q. 12. Pernicious oral habits Ans. Ans. Lip-biting habit is usually seen in cases with excessive overjet. Clinical features Proclined upper anteriors Hypertrophic and redundant lower lip Cracking of lips. Treatment Lip bumpers. Q. 10. Bruxism Ans. Grinding of teeth for non-functional purposes is known as bruxism. It is mainly due to psychological and emotional stresses or occlusal interference. Pericoronitis and periodontal pain trigger bruxism. Occlusal wear facets are seen on teeth, mobility of teeth, fractured teeth and restorations. Muscle pain on waking up in the morning, TMJ pain or discomfort, and tenderness and hypertrophy of masticatory muscles. Treatment consists of psychological counselling, relieving muscle tension by occlusal adjustments, and use of night guards or occlusal splints. Q. 11. Management of thumb-sucking habit Ans. Management of thumb-sucking habit is as follows: The child, parent and dentist together form a team to assist the child in stopping the habit. Treatment is mainly of three categories: i. Psychological therapy ii. Reminder therapy or mechanotherapy iii. Chemical approach. Orthodontics-Part-I-2013.indd 81 Pernicious oral habits are one of the factors influencing the occlusion. Abnormal oral habits like sucking habits, tongue thrusting alter the equilibrium of buccinator mechanism. Various pernicious oral habits like digit sucking, tongue thrusting and mouth breathing can cause class II division 1 features. Median diastema can also be caused due to these habits. Discontinuation of these habits is required for correction of acquired malocclusions. Q. 13. Lip bumper Ans. The lip bumper is a ‘combined, removable fixed appliance’. The appliance can be used in both the maxilla (Denholtz appliance) and the mandible to shield the lips away from the teeth. Typically it is a vestibular arch carrying an acrylic pad engaged to lower molar bands with a 0.93 mm diameter wire, it stands 2–3 mm away from the teeth and gingiva, and lies about 4 mm below the cervical margins of the lower incisors. The lower lip is thus held forward. ❍ It prevents the hyperactivity of the mentalis muscle and the abnormal force from acting on the incisors. ❍ The other effect of lip bumper is that it causes proclination of the incisors and distalization of molars. ❍ It is used in the correction or elimination of lip trap. Q. 14. Nail biting Ans. Nail biting is one of the deleterious oral habits. It does not produce gross malocclusion. It results in minor tooth irregularities similar to nut notch because of cracking hard nuts. 12/3/2013 2:49:15 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 82 It is treated with lip bumpers. Q. 15. Beta hypothesis Ans. Beta hypothesis or the concept of ‘negative practice’ was discovered by Dr Knight Dunlap (1929). Topic 10 When the concept of beta hypothesis or negative practice is applied to oral habits, it helps as a self-correcting mechanism. A child is encouraged to watch himself/herself in a large mirror while sucking the digit; the sight of oneself sucking thumb will hamper the pleasure derived from that act and the child will slowly try to avoid the habit by himself/ herself. ORTHODONTIC DIAGNOSIS LONG ESSAYS Q. 1. Classify diagnostic aids and enumerate all the essential diagnostic aids. Orthodontic Diagnostic Aids Or Classify diagnostic aids and write in detail about case history and clinical examination. Or What are the diagnostic aids used in orthodontics? Describe any one of them in detail. Or Discuss in brief about the various diagnostic aids used in orthodontic case analysis. Or Describe your procedure for clinical examination of face and intraoral tissue. Essential diagnostic aids i. Case history Non-essential diagnostic aids (supplemental diagnostic aids) i. Supplemental radiographs ii. Clinical examination a. Occlusal films (intraoral) iii. Study models b. Lateral jaw views iv. Certain radiographs: c. Cone shift technique a. IOPA radiograph b. Bitewing c. Orthopantomogram (OPG) v. Facial photographs d. Cephalometric radiographs ii. EMG (electromyographic examination of muscle activity) iii. Hand–wrist radiographs iv. Endocrine tests v. Estimation of BMR vi. Diagnostic setup Ans. vii. Occlusograms Diagnosis involves development of a comprehensive database of pertinent information. The data is derived from both essential and non-essential diagnostic aids. ESSENTIAL DIAGNOSTIC AIDS Orthodontic diagnostic aids are of two types: i. Essential diagnostic aids: These are considered very important for all the cases. These are simple and do not require expensive equipment. ii. Non-essential or supplemental diagnostic aids: These are not essential in all cases and require specialized equipment. It includes the information collected from the patient and parent or guardian to aid in the overall diagnosis of the case. Case history includes certain personal details, the chief complaint, past and present dental as well as medical history, and associated family history. Orthodontics-Part-I-2013.indd 82 Case History 12/3/2013 2:49:15 PM
  • Topic wise Solved Questions of Previous Years 83 1. Personal details a. Name The patients’ name should be recorded not only for the purpose of communication and identification, but also for addressing a patient by name has a positive beneficial psychological effect on the patient. b. Age The chronological age of the patient helps in diagnosis as well as treatment planning. Certain treatment protocols are dictated by the age of the patient like growth modification procedures using functional and orthopaedic appliances are best carried out during growth period, whereas surgical respective procedures are better carried out after the cessation of growth. c. Sex It is important in treatment planning, as the timing of growth events differs in males and females. d. Address and occupation These are important for communication and evaluation of socioeconomic status of the patient. These help in selection of appropriate appliance. 2. Chief complaint It should be recorded in patient’s own words. This helps the clinician in identifying the priorities and desires of the patients, which help in setting treatment objectives to satisfy the patients as well as their family in general. 3. Medical history A very few medical conditions contraindicate the use of orthodontic appliances. Most of the medical conditions require certain precautionary measures to be taken prior to or during orthodontic therapy, e.g. antibiotic coverage may be required in patients with rheumatic fever or cardiac anomalies even for molar band placement and removal. 4. Dental history Past dental history helps in assessing the patient and parent’s attitude towards dental health and dental treatment. Dental history should include information on the age of eruption of deciduous and permanent teeth, history of extraction, decay restoration and trauma to the dentition. The use of certain teratogenic drugs like thalidomide and some infections like German measles during pregnancy result in congenital deformities of the child. Forceps delivery predisposes to TMJ injuries and associated mandibular growth retardation. 6. Postnatal history The type of feeding. Presence of habits, e.g. digit or thumb sucking. Milestones of normal development are included in the postnatal history. 7. Family history Records the details of malocclusion existing in other members of the family, which gives a hint of inherited conditions, e.g. skeletal class II and class III malocclusions, and congenital conditions like cleft lip and palate. Clinical Examination Clinical examination of a patient includes the following: 1. General examination 2. Extraoral examination 3. Intraoral examination 4. Functional examination. 1. General examination It comprises of general assessment of the patient and usually begins as soon as the patient enters the clinic, which includes: a. Gait, b. Posture and c. Body built. a. Gait It is the way the person walks any abnormality in the gait; it suggests neuromuscular disorders that have a dental correction. b. Posture It is the way the person stands; any abnormality in posture can predispose to malocclusion due to alteration in maxilla– mandibular relationship. c. Body built Shelson has classified the general body built into three types: i. Ectomorphic—tall and thin physique. ii. Mesomorphic—average physique. iii. Endomorphic—short and obese physique. 5. Prenatal and postnatal history Prenatal history includes the information on the condition of the mother during pregnancy and type of delivery. Orthodontics-Part-I-2013.indd 83 2. Extraoral examination It includes the following: 12/3/2013 2:49:15 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 84 a. Type of the head i. Mesocephalic, i.e. average-shape head ii. Dolichocephalic, i.e. long and narrow head iii. Brachycephalic, i.e. broad and round head. b. Facial form i. Mesoprosopic (average facial form) ii. Euryprosopic (broad and short facial form) iii. Leptoprosopic (long and narrow facial form). c. Facial profile i. Straight ii. Convex iii. Concave. d. Facial divergence It is defined as inclination of lower face relative to forehead. i. Anterior divergent—class III cases ii. Posterior divergent—class II cases iii. Straight or orthognathic—class I cases. e. Assessment of facial symmetry and proportions For assessment of symmetry, the face is examined in the frontal and lateral views. In the frontal plane, intercanthal distance equals width of the nose and interpupillary distance equals width of the mouth. Vertical height of the midface should equal the height of lower face. The height of the forehead is measured from hairline to glabella; it measures one-third of the total facial height. In normally balanced face, upper facial height, middle face and lower facial height should be equal. f. Examination of lips Competent lips: Lips that are in slight contact when the musculature is relaxed. Incompetent lips: Anatomically short lips that do not contact each other when the musculature is relaxed. Everted lips: These are hypertrophied lips with redundant tissue exhibiting weak muscular tonicity. g. Examination of nose It includes examination of size, contour and nostrils. h. Examination of chin Mentolabial sulcus, mentalis activity and chin position as well as prominence should be examined. i. Nasolabial angle It is the angle formed by tangent to base of the nose and a tangent to upper lip. Normal angulation is 110°. In cases of proclination of upper incisors NLA is acute or decreased, and NLA is obtuse or increased in retroclination of incisors. j. Clinical FMA The inclination of mandibular plane angle to Frankfurt horizontal plane should be noted clinically by plac- Orthodontics-Part-I-2013.indd 84 ing measuring scales on patient’s face corresponding to respective planes. In average FMA cases, the angle meets behind the occiput. In a high-angle case, the posterior ends of the angle meet behind the auricle or within the occiput. Steep mandibular plane angle is seen in patients with long face and open bites, while flat mandibular plane angle is seen in short faces and skeletal deep bite cases. In a low-angle case, the two lines are parallel and meet very far away. The examination of profile, divergence, vertical facial proportions, lip posture, incisor protrusion and clinical FMA constitute the facial profile analysis. It is also called poor man’s cephalometric analysis. k. Chin Chin is examined for height, width and contour. Mentolabial sulcus: It is shallow in bimaxillary protrusion, while deep in class II division 1 malocclusion. Hyperactive mentalis activity is also seen along with lip habits like lip sucking and thrusting. l. Chin and soft tissues Throat form Throat length Chin–throat angle. 3. Intraoral examination a. Mouth opening Intraoral examination starts with measuring of mouth opening. Normal mouth opening is 45–55 mm for adults and less than 45 mm for children. b. Tongue The size, colour and configuration of tongue should be assessed. c. Palate Palate is assessed for contour. Palatal mucosa is examined for ulcerations, indentations, clefts or pathologic swellings. d. Gingiva The gingiva is examined for signs of inflammation, hypertrophy or recession. e. Frenal attachments Midline diastemas may arise due to thick maxillary labial frenum. High attachment of mandibular labial frenum leads to gingival recession. f. Adenoid and tonsils These are examined for enlargement and inflammation. 12/3/2013 2:49:15 PM
  • Topic wise Solved Questions of Previous Years 85 g. Dentition Number of deciduous and permanent teeth. Size, shape and form of teeth. Presence of supernumerary or missing tooth, caries, attrition, erosion, fractures, etc. h. Intra-arch examination Assessment of shape, symmetry and alignment of arch. Location of midlines, rotations of teeth, crowding, spacing and contact areas are checked. i. Interarch examination Midline shift between the maxilla and mandible is recorded. Sagittal relations: Molar relationship, canine relationship, overjet and anterior crossbite are recorded. Vertical relation: Deep bite, open bite. Transverse relation: Posterior crossbites. 4. Functional examination The dynamic nature of the stomatognathic system for optimal function is studied in functional examination. It helps in identifying the aetiology of malocclusion and therefore helps in planning the type of orthodontic treatment to be initiated. Detailed functional examination includes: i. Examination of postural rest position and maximum intercuspation ii. Examination of path of closure iii. Examination of temporomandibular joint iv. Examination of orofacial dysfunctions. i. Examination of postural rest position The position of mandible where the synergistic and antagonistic muscular components are in dynamic equilibrium with their balance being maintained by basic muscle tonus is known as postural rest position. Clinical significance In true deep bite cases, increased freeway space is seen where there is infraocclusion of posteriors. In such conditions, bite opening by molar extrusion can be attempted. Pseudo deep bite with normal freeway space has normal eruption of posteriors. Bite opening by intrusion of incisors is recommended. ii. Examination of path of closure The path of closure of mandible from the postural rest position to maximum intercuspation is evaluated in sagittal, vertical and transverse planes. Patient is examined for presence of functional shifts in the anterior, posterior or lateral direction. Examples: Upwards and forwards–normal Upwards and backwards—class II division 2 Orthodontics-Part-I-2013.indd 85 Upward forward and forwards—pseudo class III and anterior crossbites. iii. Examination of temporomandibular joint Palpation: The TMJ is palpated for tenderness and synchrony of action. Auscultation: The joint is checked for clicking or crepitus, using a stethoscope. Functional analysis of TMJ: The opening and closing movements of the mandible as well as its protrusive, retrusive and the lateral excursions are examined clinically. iv. Examination of orofacial dysfunctions Examination of orofacial dysfunction includes analysis of the functions like swallowing, speech, respiration, and actions of tongue and lips. a. Examination of swallowing pattern The normal swallowing pattern exhibits contraction of mandibular elevators; the tongue is enclosed in the oral cavity, teeth occlude momentarily and dorsum of the tongue approaches the palate. Infants swallow in a different manner. Retained infantile swallow leads to malocclusion. Signs of infantile swallow: Jaws are apart while swallowing, tongue is placed between the teeth, mandible is stabilized by contraction of lips and tongue, muscles of facial expression are involved, and there is anterior mandibular thrust along with caving-in of cheeks. b. Examination of tongue The size, shape, posture and function of the tongue are assessed. 1. Tongue size and shape: Abnormal tongue size like microglossia, i.e. small tongue and collapsed arch, and macroglossia exhibits spaced dentition and crenations in lateral border of tongue. 2. Tongue position or posture Position of tongue is very important factor in development of malocclusion. Normal resting position of tongue is retracted tip just behind the lower incisors and lateral border resting on the linguo-occlusal surfaces of lower posterior teeth. In cases of class II malocclusion, tongue tip is more retruded at rest position while it lays far forward in class III cases. 3. Tongue function (thrust) The various types of tongue thrust are present like anterior, lateral, complex, endogenous, habitual and adaptive tongue thrust. Anterior tongue thrust is associated with anterior open bite. Lateral open bite is seen in lateral tongue thrust. Complex tongue thrust patient occludes teeth only in the molar region. 12/3/2013 2:49:15 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 86 c. Examination of lips Examination of lips consists of assessment of configuration, functioning and presence of any dysfunctions. The common lip dysfunctions include lip sucking, lip thrust and lip insufficiency. d. Examination of respiration The mode of respiration is examined to establish any impediment in nasal breathing. Mouth breathing results due to prolonged difficulty in nasal breathing. This type of breathing results in disturbed orofacial musculature, which leads to long face syndrome or adenoid facies. e. Examination of speech In structural defects involving the palate, tongue, lips and dentition, etc., the speech is affected and the area of abnormality is identified by observing pronunciations of different consonants. Example: Patients having tongue thrust habit tend to lisp while cleft palate patients may have a nasal tone. Q. 2. Discuss the importance of intraoral X-rays in orthodontic diagnosis and treatment planning. Or What are the diagnostic aids used in orthodontics? Describe anyone of them. Or Describe role of X-rays in orthodontic diagnosis and OPG in detail. Ans. Diagnosis involves development of a comprehensive database of pertinent information. The data is derived from both essential and non-essential diagnostic aids. Orthodontic diagnostic aids are of two types: i. Essential diagnostic aids: These are considered very important for all the cases and are simple and do not require expensive equipment. ii. Non-essential or supplemental diagnostic aids: These are not essential in all cases, and require specialized equipment. Role of radiographs in orthodontic diagnosis The uses of radiographs in orthodontics are: To assess general development of the dentition, presence, absence and state of eruption of the teeth. To determine the extent of root resorption of deciduous teeth and the extent of root formation of the permanent teeth. To confirm the diagnosis of any supernumerary teeth, teeth that are morphologically abnormal extent of pathological and traumatic conditions. Orthodontics-Part-I-2013.indd 86 To study the character of alveolar bone. These are a valuable aid in cranio–dento–facial analysis. CLASSIFICATION OF RADIOGRAPHS Various radiographs used in orthodontics are classified as follows: 1. Based on the location of the radiographic film a. Intraoral radiographs i. Intraoral periapical (IOPA) radiographs ii. Bitewing radiographs iii. Occlusal radiographs. b. Extraoral radiographs i. Panoramic radiographs ii. TMJ radiographs iii. Cephalograms. 2. Based on the area of interest a. IOPA radiographs b. Bitewing radiographs c. Occlusal radiographs d. Panoramic radiographs e. Radiographs to assess the facial skeleton i. Lateral cephalometric radiographs ii. Frontal cephalometric radiographs iii. Oblique cephalometric radiographs. 3. Based on importance in diagnosis a. Essential diagnostic radiographs i. IOPA radiographs ii. Bitewing radiographs iii. Panoramic radiographs. b. Supplementary diagnostic radiographs i. Occlusal radiographs ii. Cephalometric radiographs iii. Hand–wrist radiographs iv. TMJ radiographs. A. Role of Intraoral Radiographs in Orthodontics Intraoral radiographs are called so because they are taken with the film placed inside the patient’s mouth. They provide vital information about the teeth and their supporting structures. Commonly there are three types of intraoral radiographs used in orthodontics: i. Intraoral periapical radiographs (IOPA) ii. Bitewing radiographs iii. Occlusal radiographs. i. IOPA radiographs These are the most commonly used radiographs in dentistry to visualize the teeth and the supporting alveolar bone. Uses of IOPA radiographs are as follows: To examine the amount of demineralization in carious tooth 12/3/2013 2:49:15 PM
  • Topic wise Solved Questions of Previous Years 87 To assess the height of alveolar bone crest around the tooth To study the extent of root resorption and root formation in the deciduous and permanent teeth, respectively To visualize the root for any fractures or external resorption To examine any calcific changes or internal resorption in the dental pulp To visualize the apical area of teeth to rule out pathology To view the size, location and angulation of impacted teeth To study quality of alveolar bone and periodontal ligament space To confirm the congenital absence of teeth or presence of supernumerary tooth. Advantages of IOPA are as follows: The area of interest can be visualized in high detail. Minimal radiation exposure to patient. Easy to store and transport. Disadvantages of IOPA are as follows: While placing the film, pain and gagging may occur. Many radiographs are required for full-mouth survey. Exposure to radiation increases when used for full-mouth examination. There are two methods of obtaining IOPA radiographs: 1. Paralleling technique 2. Bisecting angle technique. Paralleling technique In this technique the X-ray film is placed parallel to the long axis of the teeth and the central ray of the collimated X-ray beam is passed perpendicular to long axis of the tooth and the film. In this technique there is reduced geometric distortion. Morphological limitations imposed by oral cavity in the correct placement of the film. Bisecting angle technique This technique uses Cieszynski’s rule of isometry, which is a geometric theorem. According to the rule of isometry, two triangles are equal when they share a complete side and two equal angles. In this technique, the central ray is directed at right angles to a plane bisecting the angle between the long axis of the teeth and the film. This technique is convenient to the operator and the film is placed close to lingual surfaces of the tooth. The disadvantage of this technique is that faulty X-ray beam angulation results in foreshortening or elongation of the image. Uses of bitewing radiographs are as follows: Bitewing radiographs are used for detecting: Interproximal caries at an early stage and secondary caries under restorations. Bone loss at the alveolar crest. Calculus deposits and overhangs in the restoration at the interproximal areas. Occlusal pattern. Advantages of bitewing radiographs are: No geometric distortions and magnifications. Convenient to the operator and comfortable to the patient. When compared to periapical films, it is easier to use in children. iii. Occlusal radiographs When there is a need to visualize a large segment of the dental arch with reasonable extent of adjacent structures, occlusal radiograph is indicated. The radiographic film 3 × 2 inches in size is placed between the occlusal surfaces of the teeth in the plane of occlusion. Classification of occlusal radiographs based on the projection of the X-ray is as follows: i. Maxillary occlusal radiographs Topographical maxillary occlusal projection Cross-sectional maxillary occlusal projection. ii. Mandibular occlusal radiographs Topographical mandibular occlusal projection Cross-sectional mandibular occlusal projection Mental spine view Uses of occlusal radiographs are as follows: To locate impacted or unerupted or supernumerary teeth. To locate foreign bodies in the jaws and calculi in salivary ducts. To study clearly buccal or buccolingual expansions of cortical plate due to pathological lesions of the jaw. To diagnose the extent of fractures. They are useful in orthodontics to analyse treatment effects of arch expansion procedures. They are helpful in patients with limited mouth opening. Only minimal error is possible. Used to observe abnormal eruption pattern of the canines and also to differentiate buccal or lingual positioning of tooth. B. Extraoral Radiographs ii. Bitewing radiographs Bitewing radiographs give information about the tooth and the supporting alveolar bone up to half the length of the root. Orthodontics-Part-I-2013.indd 87 Commonly used extraoral radiographs are: i. Panoramic radiographs ii. Cephalograms and iii. TMJ radiographs. 12/3/2013 2:49:16 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 88 i. Panoramic radiographs The panoramic radiography was introduced by Dickson and Coppola. It is a radiographic procedure used to record a single image that covers major part of facial region. The maxillary and mandibular arches and their supporting structures are all visualized in a single film. Procedure Position the patient’s head in the panorex machine by making the patient stand or sit, biting the bite-fork with the incisors. An X-ray source rotates around the patient’s head. The rate at which the X-ray source moves is kept the same as the rate at which the film rotates. The image seen on the film is composed of anatomic structures lying along predetermined curved image zone called focal trough. Uses Used for evaluation of dental development in the mixed dentition by assessing the extent of root resorption in the primary teeth and amount of root formation in the permanent teeth. To locate supernumerary tooth or congenitally missing tooth or impacted tooth. It is used to assess the development and position of third molars. To detect presence of pathologic lesions in the jaw bones and to ascertain its extent. Also useful in diagnosis of jaw bone fractures. It is used to locate carious lesions, bone loss due to periodontal diseases, retained deciduous tooth, etc. Advantages The amount of radiation exposure to the patient is low when compared to full-mouth intraoral periapical radiographs. Highly valuable as an initial survey radiograph, as broad anatomic area can be visualized. It is useful in patients with extreme gag reflex and those unable to open the mouth, i.e. trismus. Disadvantages The teeth and the supporting periodontal structures are not as clear as in periapical films. Hence, orthopantomogram (OPG) is not suitable for diagnosis of lesions requiring high resolution, e.g. early alveolar bone loss. Image magnification, minimization or blurring of incisor teeth may take place. Radiopaque shadows are formed by structures like earrings, ramus of mandible, spinal cord, etc. Overlapping of the adjacent structures occurs. It requires very expensive equipment. Anterior teeth inclination cannot be visualized. Orthodontics-Part-I-2013.indd 88 ii. Cephalometric radiographs ‘Cephalo’ means head and ‘metric’ means measurement. The measurement of the head from the shadows of the bony and soft tissue landmark on the radiographic image is known as roentgenographic cephalometry. These are specialized radiographs of skull in which the head is positioned in a specially designed head holder called cephalostat. Thus, it is a standardized technique in which the head is held in a predetermined position. Cephalograms are also used for longitudinal studies, i.e. comparison of serial radiographs. Cephalometric radiographs are of two types: 1. Lateral cephalogram 2. Posteroanterior cephalogram. Q. 3. Enumerate various diagnostic aids used in orthodontics. Add a note on study models. Or Enumerate essential diagnostic aids. Describe study models in detail. Or Classify the diagnostic aids in orthodontics. Write the importance of study models and enumerate various types of models used in orthodontics. Ans. “Study models are accurate reproduction of teeth and their surrounding soft tissues that provide a reasonable ‘facsimile’ of the occlusion of the patient.”—Graber These are essential diagnostic aids, and have a prominent role in diagnosis and treatment planning. Before skull radiography became popular, they were in widespread use. Study casts reproduce the teeth and surrounding structures with a fair degree of accuracy. Even in the absence of the patient, the clinician can study the occlusion from all directions using the study casts. The parts of a study model are: i. Anatomic portion ii. Artistic portion. i. Anatomic portion: It is the actual replica of the patient’s teeth and supporting structures obtained by impression. It is usually made of stone plaster. ii. Artistic portion: Artistic portion is nothing but plaster base around the anatomic portion. The artistic portion supports the anatomic portion and orients it in a manner that is pleasing to eye. In a well-trimmed study cast, the ratio between anatomic portion and artistic portion should be 2:1. The tooth portion, soft tissue portion and the artistic portion are related 12/3/2013 2:49:16 PM
  • Topic wise Solved Questions of Previous Years 89 in 1:1:1 manner. The completed model should be 13 mm in height in the anterior and posterior region. The steps involved in fabrication of study casts are as follows: i. Impression making ii. Disinfection of the impression iii. Casting the impression iv. Basing and trimming of the cast v. Finishing and polishing. Impression making Obtaining a good impression is an essential factor in the proper fabrication of orthodontic casts. Care must be taken to obtain as nearly a perfect reproduction of teeth and investing tissues as possible. Use of a mouth wash prior to impression removes debris and reduces surface tension on tooth surface, cutting down bubble formation during impression making. Alginate impressions are ideally suited for this. A quick-setting type with a time span not exceeding 90 seconds from mixing to completion of the mix. The orthodontic study models should reproduce as much of the supporting structures as possible; hence, it is recommended to use high flange orthodontic trays that extend deep into buccal and lingual sulci. The selected trays should include the last erupted molars and should have clearance of around 3 mm between teeth and the tray. A good maxillary and mandibular impression will show a peripheral roll and record the muscle attachments. The retromolar pads in the lower jaw and the tuberosity in the upper jaw should be included. Disinfecting the impression The impression is rinsed thoroughly in water and then disinfected to remove microorganisms, plaque, mucin and other debris that might reduce the quality of surface reproduction. Disinfectant solution such as biocide may be used for this purpose. After disinfection, once again the impressions are rinsed in water to clear any residual disinfectant. Casting the impression The impression is rinsed and the excess water is shaken out. A good grade of white stone model plaster is usually satisfactory to pour the impression. It is best to use a mechanical spatulator or vacuum mixer; if this is not available, it is beneficial to use some form of vibrator. The mechanical vibrator not only eliminates incorporation of the air bubbles but also permits the use of heavier mix, which is much easier to handle in pouring up and producing a strong cast. Orthodontics-Part-I-2013.indd 89 Basing and trimming of the cast The rubber base formers are readily available to pour the art portion or base. They serve to confine the plaster and are fabricated to shape the base in artistically pleasing contours. Orientation of the tray is done in such a way that the anatomic portion is in the centre of the rubber mould, with the occlusal plane parallel with the cast base of the base former. The various types of base formers used are: Broussard case former, the Columbia anterior segment single unit study cast former. Guidelines for trimming of the casts are as follows: Some orthodontists prefer individualizing casts because of additional information that can be gained and more accurate orientation with the occlusal plane parallel with cast base. These modifications require a cast trimmer or a set of a plaster files. The procedure of trimming is as follows: i. The upper model is cut with the back edge at right angles to the middle line of the palate; and the front surfaces are cut so that the point of intersection of the front surfaces is in line with the middle line of the palate. ii. The sides of the model are cut symmetrically about the middle line. iii. The upper model is used as a guide in trimming the lower model. iv. By using the set square, the back corners of the upper and lower models are trimmed simultaneously. The front of the lower model is trimmed to a smooth curve. iv. The distal corners are cut symmetrically to the middle line conveniently, with the models in occlusion. The sides of the model are cut symmetrically about the middle line. v. The occlusal plane should be parallel to the top and bottom of the study casts. vi. After trimming, the study casts should be symmetrical. Upper study cast should have seven sides and lower study cast should have six sides when viewed from the occlusal plane. Finishing and polishing of the cast Final finishing of artistic portion of dental casts can be done with fine-grained waterproof sand paper. Bubbles that appear at the gingival margin should be removed with a small universal sealer; and those in the mucobuccal fold area can be removed with a Kingsleytype scraper. Final polishing is done by placing the casts in soap solution for 1 hour and is later removed and rinsed under warm water. The casts are then dried and buffed so that they acquire smooth and shiny surface. Model storage boxes are used to store the finished study models for future reference. 12/3/2013 2:49:16 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 90 Uses Ans. Uses of study casts are as follows: Study casts are considered as one of the essential diagnostic aids in orthodontic diagnosis and treatment planning. As they provide a three-dimensional precise record of the teeth and their supporting structures, they enable the study of the occlusion from all aspects. They help in assessing the nature and severity of malocclusion. They are valuable aids in patient education and motivation by enabling to explain the treatment plan as well as progress to the patient and parents. It makes it possible to simulate surgical treatment procedures on the cast such as mock surgery. Study models help in communication between orthodontists to transfer records in case the patient is to be treated by another clinician. They help in assessment of treatment progress by the dentist as well as the patient. They are used in mixed dentition analyses along with charts and radiographs. Diagnosis involves development of a comprehensive database of pertinent information. The data is derived from both essential and non-essential diagnostic aids. Advantages Compared to clinical examination or photographs, the study casts permit a more objective assessment of malocclusion. They make it possible to view the patient’s occlusion from all the aspects, which is impossible in patient’s mouth. They are a permanent record of the patient’s malocclusion and can be duplicated easily when needed. They are economical. Disadvantages Considerable storage space is required to preserve them. With mass storage, retrieval takes time and there is possibility of breakage. No detailed information is provided about soft tissues in the oral cavity. No relationship can be elicited between teeth and the facial profile. Q. 4. What do you understand by diagnostic aids? Classify them. Describe the role of cephalometrics in orthodontics. Or What are the diagnostics aids? Describe in detail about cephalometrics and its uses in orthodontics. Or Classify diagnostic aids in orthodontics. Describe the uses of roentgenographic cephalometry in orthodontics. Orthodontics-Part-I-2013.indd 90 Orthodontic diagnostic aids are of two types: i. Essential diagnostic aids: They are considered very important for all the cases. They are simple and do not require expensive equipment. ii. Non-essential or supplemental diagnostic aids: They are not essential in all cases and require specialized equipment. Orthodontic Diagnostic Aids Essential diagnostic aids Non-essential diagnostic aids (supplemental diagnostic aids) i. ii. iii. iv. i. Supplemental radiographs a. Occlusal films (intraoral) b. Lateral jaw views c. Cone shift technique d. Cephalometric radiographs ii. EMG (electromyographic examination of muscle activity) iii. Hand-wrist radiographs iv. Endocrine tests v. Estimation of BMR vi. Diagnostic setup vii. Occlusograms Case history Clinical examination Study models Certain radiographs: a. IOPA radiograph b. Bitewing c. Orthopantomogram (OPG) v. Facial photographs Cephalometrics Holly Broadbent of the United States and Herbert Hofrath of Germany in 1931 introduced the roentgenographic cephalometric technique to orthodontics. ‘Cephalo’ means head and ‘metric’ means measurement. The measurement of the head from the shadows of the bony and soft tissue landmarks on the radiographic image is known as roentgenographic cephalometry. Cephalometric radiographs have become an integral part of orthodontic practice and enable the clinicians to quantify facial and dental relationships. These provide information about the spatial relationship of superficial and deep structures. Various types of cephalograms are as follows: i. Lateral cephalogram ii. Frontal or anteroposterior cephalogram iii. Oblique cephalogram. Technique of cephalometric radiography An apparatus that consists of an X-ray source and a headholding device called cephalostat is used to take a cephalometric radiograph. 12/3/2013 2:49:16 PM
  • Topic wise Solved Questions of Previous Years 91 The cephalostat prevents the movement of the head in the horizontal plane. Vertical stabilization of the head is brought about by an orbital pointer that contacts the lower border of the left orbit. The upper part of the face is supported by the forehead clamp positioned above the region of the nasal bridge. The equipment helps in standardizing the radiographs by use of constant head position and a fixed-source film distance (5 feet) so that serial radiographs can be compared. Uses of cephalograms are as follows: Cephalometrics is one of the valuable tools in treatment planning and follow-up of patients undergoing orthodontic treatment. Cephalogram is used to elucidate the skeletal, dental and soft-tissue relationships of the craniofacial region, and helps in identification and classification of skeletal and dental anomalies. They are useful in estimating the facial type. They help in treatment planning and evaluation of the treatment results for an individual. Serial cephalograms help in assessment of growth of facial skeleton and are also used in growth prediction. They help in predicting the growth-related changes and changes associated with orthognathic surgical treatment; and they also help to distinguish changes produced by natural growth and orthodontic treatment. Cephalograms also help to carry out functional analysis. Cephalograms are relatively non-destructive and non-invasive, producing a high yield of information at relatively economical cost. Cephalograms are relatively permanent records and are easy to store, transport and reproduce. Cephalometrics is a valuable aid in research work involving the cranio–dento–facial region. Limitations/drawbacks of cephalograms It should be used only when it is diagnostically and therapeutically desirable, as the patient is exposed to ionizing radiation, which is harmful. Due to lack of anatomical references that remain constant with time, it is a serious disadvantage when clinicians wish to compare cephalograms taken at different times. Some reference landmarks and planes do not agree with the anatomical landmarks. The processes of image acquisition as well as measurement procedures are not well-standardized. It is difficult to locate landmarks and surfaces on the X-ray image, as the image lacks hard edges and well-defined outlines. The radiographic image is two-dimensional picture of three-dimensional structures being imaged. Anatomical structures lying at different planes within the head undergo projective displacement. There could be a mandibular shift from centric relation, as the patient is made to bite in maximum intercuspation while taking the cephalogram. A cephalometric analysis makes use of means obtained from different population samples. They have only limited relevance when applied to individual patient. The composite of lines and angles used in the cephalometric analysis yields limited information about the patient’s dentoskeletal patterns. An orthodontic diagnosis cannot be made solely on the basis of cephalometric analysis. SHORT ESSAYS Q. 1. Electromyography Ans. The procedure used for recording the electrical activity of the muscles when they are excited is known as electromyography (EMG). The instrument used is called electromyograph and the output is called electromyogram. The electromyograph is a machine used to receive, amplify and record the action potential during muscle activity. The record obtained by such a procedure is known as electromyogram. The surface membrane of the muscle cells is positively charged on the external surface and negatively charged on the internal surface. The action potential reverses the charge on the muscle membrane. A series of changes that Orthodontics-Part-I-2013.indd 91 occur will bring about muscle contraction. Recording of the electrical charges from the muscle are accomplished by means of surface electrodes or needle electrodes. i. Surface electrodes: These electrodes are used when the muscle is superficially placed just below the skin. ii. Needle electrodes: They are used when the muscle is placed deep inside, e.g. pterygoid muscles. The action potential is picked up by surface or needle electrodes, and is recorded either with the help of a moving pen in the form of a graph or in the form of sound with the help of a magnetic tape recorder. Permanent paper record is obtained with a pen writing device. Electromyogram can be displayed on an oscilloscope. 12/3/2013 2:49:16 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 92 Uses of EMG The role of musculature in craniofacial growth can be studied with the help of EMG. In mouth breathers, EMG is used to study the activity of mandibular elevators and depressors. EMG is used to assess the aberrant muscular activity associated with various habits. Abnormal muscle activity associated with certain forms of malocclusion can be detected with the help of EMG. Examples: ❍ Abnormal buccinator activity in class II, division 1. ❍ The hypofunctional upper lip in severe class II division 1 malocclusion. Following orthodontic therapy EMG can be carried out to see if muscle balance is achieved. Disadvantages of EMG Unknown levels of muscular fatigue or pain may compromise EMG readings. Muscle activity varies at different periods even in the day time. Measures of EMG activity during clenching, swallowing, etc. varies considerably between subjects. Q. 2. Diagnostic aids in orthodontics Or What are orthodontic diagnostic aids? Enumerate essential diagnostic aids. Or Essential diagnostic aids Ans. Diagnosis involves development of a comprehensive database of pertinent information. The data is derived from both essential and non-essential diagnostic aids. Orthodontic diagnostic aids are of two types: 1. Essential diagnostic aids: They are considered very important for all the cases. These are simple and do not require expensive equipment. 2. Non-essential or supplemental diagnostic aids: These are not essential in all cases and require specialized equipment. Essential diagnostic aids 1. Case history 2. Clinical examination 3. Study models 4. Certain radiographs: a. IOPA radiograph b. Bitewing c. OPG 5. Facial photographs. Orthodontics-Part-I-2013.indd 92 Q. 3. What are the study models and their uses in orthodontics? Or Study models Ans. “Study models are accurate reproduction of teeth and their surrounding soft tissues that provide a reasonable ‘facsimile’ of the occlusion of the patient”.—Graber Study casts reproduce the teeth and surrounding structures with a fair degree of accuracy. Even in the absence of the patient, the clinician can study the occlusion from all directions using the study casts. Parts of study model are as follows: i. Anatomic portion ii. Artistic portion. Anatomic portion is the actual replica of the patient’s teeth and supporting structures obtained by impression. Artistic portion is nothing but plaster base around the anatomic portion. The steps involved in fabrication of study casts are as follows: i. Impression making ii. Disinfection of the impression iii. Casting the impression iv. Basing and trimming of the cast v. Finishing and polishing. Uses of study casts are as follows: Study casts are considered as one of the essential diagnostic aids in orthodontic diagnosis and treatment planning. As they provide a three-dimensional precise record of the teeth and their supporting structures, they enable the study of the occlusion from all aspects. They help in assessing the nature and severity of malocclusion. They are valuable aids in patient education and motivation by enabling to explain the treatment plan as well as progress to the patient and parents. It makes it possible to simulate surgical treatment procedures on the cast such as mock surgery. Study models help in communication between orthodontists to transfer records in case the patient is to be treated by another clinician. They help in assessment of treatment progress by the dentist as well as the patient. They are used in mixed dentition analyses along with charts and radiographs. 12/3/2013 2:49:16 PM
  • Topic wise Solved Questions of Previous Years 93 Q. 4. Discuss supplementary diagnostic aids used in orthodontics. Ans. Supplementary diagnostic aids are certain aids that are not essential in all cases. They may require specialized equipment that an average dentist may not possess. The supplemental diagnostic aids are as follows: Specialized radiographs i. Cephalometric radiographs ii. Occlusal intraoral films iii. Selected lateral jaw views iv. Cone shift technique. Electromyographic examination of muscle activity Hand–wrist radiographs to assess bone age or maturation age Endocrine tests Estimation of basal metabolic rate Diagnostic setup Occlusograms. Q. 5. Uses of radiographs in orthodontics Or Role of X-rays in orthodontics Ans. Role of radiographs in orthodontic diagnosis The uses of radiographs in orthodontics are as follows: To assess general development of the dentition, presence, absence and state of eruption of the teeth. To determine the extent of root resorption of deciduous teeth and the extent of root formation of the permanent teeth. To confirm the diagnosis of any supernumerary teeth, teeth that are morphologically abnormal, extent of pathological and traumatic conditions. To study the character of alveolar bone. They are a valuable aid in cranio–dento–facial analysis. Q. 6. Intraoral X-rays in orthodontics Ans. Intraoral radiographs are called so because they are taken with the film placed inside the patient’s mouth. Commonly there are three types of intraoral radiographs used in orthodontics: i. Intraoral periapical radiographs ii. Bitewing radiographs iii. Occlusal radiographs Orthodontics-Part-I-2013.indd 93 Intraoral periapical (IOPA) radiographs These are most commonly used radiographs in dentistry to visualize the teeth and the supporting alveolar bone. Uses of IOPA radiographs are as follows: To examine the amount of demineralization in carious tooth. To assess the height of alveolar bone crest around the tooth. To visualize the root for any fractures or external resorption or periapical pathology. To view the size, location and angulation of impacted teeth. To confirm the congenital absence of teeth or presence of supernumerary tooth. Bitewing radiographs Bitewing radiographs give information about the tooth and the supporting alveolar bone up to half the length of the root. Uses of bitewing radiographs are as follows: Bitewing radiographs are used for detecting: Interproximal caries at an early stage and secondary caries under restorations. Bone loss at the alveolar crest. Calculus deposits and overhangs in the restoration at the interproximal areas. Occlusal pattern. Occlusal radiographs When there is a need to visualize a large segment of the dental arch with reasonable extent of adjacent structures, occlusal radiograph is indicated. Uses of occlusal radiographs are as follows: To locate impacted or unerupted or supernumerary teeth, foreign bodies in the jaws and calculi in salivary ducts. To clearly study buccal or buccolingual expansions of cortical plate due to pathological lesions of the jaw. These are useful in orthodontics to analyse treatment effects of arch expansion procedures. These are helpful in patients with limited mouth opening. Q. 7. Hand–wrist radiographs Ans. Among the various skeletal maturity indicators, hand– wrist radiographs are commonly used in orthodontics. The numerous small bones in the hand–wrist region show a predictable and scheduled pattern of appearance, ossification and union from birth to maturity. Thus, by comparing patient’s hand–wrist radiograph with standard radiographs that represents different skeletal 12/3/2013 2:49:16 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 94 ages, the skeletal maturation status of the individual can be determined. Among various methods described to assess skeletal maturity using hand–wrist radiographs, the most commonly used ones are as follows: i. Atlas method by Greulich and Pyle ii. Bjork, Grave and Brown method iii. Fishman’s skeletal maturity indicators iv. Hagg and Taranger method. Atlas method by Greulich and Pyle Greulich and Pyle published an atlas, which contains pictures of the hand–wrist for different chronological ages for both the sexes. The patient’s radiographs are matched with one of the photographs in the atlas, which is representative of a particular skeletal age. Bjork, Grave and Brown method According to Bjork, the skeletal development in the hand– wrist area is divided into eight stages; each of them represents a particular level of skeletal maturity. Fishman’s skeletal maturity indicators Leonard S Fishman proposed a system for evaluation of skeletal maturation by making use of anatomical sites located on the thumb, third finger, fifth finger and radius. Covering entire period of adolescent development, 11 discrete skeletal maturity indicators have been described. Hagg and Taranger method Hagg and Taranger noted that skeletal development in hand and wrist can be analysed from assessment of ossification of ulnar sesamoid of metacarpophalangeal joint of the first finger (S) and certain specified stages of three epiphyseal bones: the middle and distal phalanges of the third finger (MP3 and DP3) and the distal epiphysis of the radius (R) by taking annual radiographs between 6 and 18 years of age. Indications of hand–wrist radiographs are as follows: It is indicated when there is a major discrepancy between the dental age and the chronological age of the patient. For determination of skeletal maturity status to assess the potential for growth prior treating the patient with skeletal class II or class III malocclusion. To predict the pubertal growth spurt. To assess the skeletal age in a patient whose growth is affected by infections or neoplasms or traumatic conditions. To evaluate growth status prior to orthognathic surgery in young adult, so that the chances of relapse linked to postsurgical growth can be minimized. Serial assessment of skeletal age is used in studying growth of an individual. It is a valuable aid in research aimed at studying the effect of heredity, environment, nutrition, etc. on the skeletal maturation pattern. Orthodontics-Part-I-2013.indd 94 Q. 8. Trimming of study model Ans. Basing and trimming of the cast The rubber base formers are readily available to pour the art portion or base. They serve to confine the plaster and are fabricated to shape the base in artistically pleasing contours. There are various types of base formers in use. For example: Broussard case former, the Columbia anterior segment single unit study cast former. The trimming of the orthodontic model is carried out on an electric plaster trimming machine having a medium grit carborundum wheel. Guidelines for trimming of the orthodontic casts are as follows: Step 1 Orientation of the tray is done in such a way that the anatomic portion is in the centre of the rubber mould, with the occlusal plane parallel with the cast base of the base former. The lower model is inverted over a ‘T’-shaped piece of rubber and a marking is circumscribed all around the base of the model using a marker mounted on a vertical stand. Once the marking is made, the base of the cast is trimmed up to the marking. Step 2 The back of the mandibular model is trimmed perpendicular to the midline leaving 5 mm of the plaster base distal to the most posterior teeth. The back of the model should be at 90° to the base of the model. Step 3 Occlude both the upper and lower models together and trim the maxillary back surface so that it is in flush with the mandibular back. Step 4 The upper and lower models are occluded together and are placed on the model trimmer with their backs. The base of the maxillary cast is trimmed so that it is parallel to the base of the lower model. At the end of this step, the backs of both the upper and lower casts are at right angles to the bases. The bases of the maxillary and the mandibular casts are parallel to each other and to the occlusal plane. Step 5 The buccal cuts are made on the mandibular cast 5–6 mm away from the buccal surface of the posterior teeth and at an angulation of 60° to the back of the model. 12/3/2013 2:49:16 PM
  • Topic wise Solved Questions of Previous Years 95 Step 6 The anterior portion of the lower arch is trimmed into a curve that follows the curvature of the lower anterior teeth and is 5–6 mm away from the labial surface of the anterior teeth. Step 7 The posterior cuts of the mandibular model measuring 13– 15 mm are trimmed at an angle of approximately 115° to the back of the model. Step 8 The buccal cuts are made at an angle of 65° to the back of the maxillary cast at a distance of 5 mm away from the buccal surface of the most posterior teeth. Step 9 On the maxillary cast, the anterior cuts are made at an angle of 30° to the back of the cast. The cuts on either side should be of equal length and 5–6 mm away from the labial surface of the anterior teeth. The anterior cuts on either side should meet at the midline of the cast and should extend till the midline of the canine. Step 10 The posterior cuts of the maxillary cast are made in such a way that they are in flush with the posterior cuts of the mandibular cast. This is done by occluding the models and trimming the maxillary posterior cuts till they are in line with the mandibular posterior cuts. After trimming the study casts should be symmetrical. Upper study cast should have seven sides and lower study cast should have six sides when viewed from occlusal plane. Q. 9. Advanced diagnostic aids Ans. The advanced diagnostic aids or the newer techniques used in orthodontic diagnosis are as follows: 1. Xeroradiography 2. MRI 3. CT scan 4. Computerized cephalometric systems 5. Photocephalometry 6. Cinefluororadiography 7. Laser holography. Xeroradiography Xeroradiography was invented by Chester Carlson for copying purposes. Xeroradiography is a radiographic method that works in a manner similar to Xerox machines; no radiographic film is employed, rather a printout is taken on paper. Orthodontics-Part-I-2013.indd 95 Method A light-tight cassette with the photoreceptor is placed intraorally and X-ray exposed like film. On exposure to the X-rays, selective discharge occurs from the areas of photoreceptors proportional to the density of the rays. The latent image is formed together from the areas with discharge and without discharge, and is converted to visible image by exposing it to charged powder particles in toner. The toner image is then transferred from the photoreceptor and fixed to a white plastic substrate for viewing. The photoreceptor is available for reuse after cleaning. Uses Xeroradiography is a valuable alternative to conventional radiography for detecting all pathologies. It is also useful in interpreting periapical structures. Advantages Wide-exposure latitude, high-edge enhancement and good detail. Choice of positive and negative displays. Compared to conventional radiographs, it requires only about one-third of the radiation dose. Magnetic resonance imaging Magnetic resonance imaging (MRI) is a non-radiographic method used to visualize the craniofacial structures. The major constituent of the body is water, which has two hydrogen atoms; each one has a single proton. The hydrogen protons behave like small magnets when they are placed in magnetic field and move around the magnetic field inducing a minute current, which is amplified and displayed on an oscilloscope. Uses Useful in studying internal derangements of the articular disc of TMJ. Used to evaluate the position of the articular disc before and after treatment with functional and orthopaedic appliances. Examination of tongue movements during deglutition. Advantages No radiation exposure. Compared to CT scanning, greater tissue characterization and a better spatial resolution. Any choice of sectional view can be created in any desired direction in the human body. Disadvantages Not useful to visualize bony lesions. Contraindicated in patients with cardiac pacemakers. Compared to CT scanning, it is more time consuming and expensive. 12/3/2013 2:49:16 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 96 Computed tomography Computed tomography (CT) is the radiographic examination of section or slice of body structures in the crosssectional form. Digital data is produced by using scanners that measure the extent of X-ray transmission through the object. Uses Useful to examine TMJ. Evaluation of amount of cortical bone for orthodontic implants. Diagnosis and treatment planning in maxillary canine impactions. To study the effects of rapid maxillary expansion and distraction osteogenesis devices. Advantages Large amount of useful information is secured in very short period with high geometric precision. Very well discriminates between objects with minor difference in density. Images can be manipulated by highlighting or accentuating areas of interest. Disadvantages Radiation exposure. Procedure is very expensive. SHORT NOTES Q. 1. Diagnostic aids Ans. Diagnosis involves development of a comprehensive database of pertinent information. The data is derived from both essential and non-essential diagnostic aids. Orthodontic diagnostic aids are of two types: i. Essential diagnostic aids: These are considered very important for all the cases. They are simple and do not require expensive equipment. Example: Case history, clinical examination, study models, etc. ii. Non-essential or supplemental diagnostic aids: These are not essential in all cases and require specialized equipment. Example: Cephalometric radiographs, EMG, hand–wrist radiographs, etc. Q. 2. Study models Or Uses of study models Ans. “Study models are accurate reproduction of teeth and their surrounding soft tissues that provide a reasonable ‘facsimile’ of the occlusion of the patient”.—Graber Parts of a study model are: (i) anatomic portion and (ii) artistic portion. Uses of study casts are as follows: i. These are one of the essential diagnostic aids in orthodontic diagnosis and treatment planning. Orthodontics-Part-I-2013.indd 96 ii. These enable the study of the occlusion from all aspects and help in assessing the nature and severity of malocclusion. iii. These are valuable aids in patient education, motivation and assessment of treatment progress. iv. These help in communication between orthodontists. Q. 3. Occlusal X-rays Or Occlusal radiographs Ans. Occlusal radiographs are one of the intraoral type of radiographs used when there is a need to visualize a large segment of the dental arch with reasonable extent of adjacent structures. The radiographic film 3 × 2 inches in size is placed between the occlusal surfaces of the teeth in the plane of occlusion. Uses of occlusal radiographs are as follows: i. To locate impacted or unerupted or supernumerary teeth and as well as foreign bodies in the jaws and calculi in salivary ducts. ii. To clearly study buccal or buccolingual expansions of cortical plate due to pathological lesions of the jaw. iii. To diagnose the extent of fractures. iv. These are useful in orthodontics to analyse treatment effects of arch expansion procedures. v. These are helpful in patients with limited mouth opening. 12/3/2013 2:49:16 PM
  • Topic wise Solved Questions of Previous Years 97 Q. 4. CT or CAT Ans. Computed tomography (CT) or computed axial tomography (CAT) is the radiographic examination of section or slice of body structures in the cross-sectional form. Digital data is produced by using scanners that measure the extent of X-ray transmission through the object. Uses of CT Useful to examine TMJ. Evaluation of amount of cortical bone for orthodontic implants. Diagnosis and treatment planning in maxillary canine impactions. To study the effects of rapid maxillary expansion and distraction osteogenesis devices. Q. 5. Orthopantomogram Or OPG 1. Based on the location of the radiographic film a. Intraoral radiographs i. Intraoral periapical (IOPA) radiographs ii. Bitewing radiographs iii. Occlusal radiographs b. Extraoral radiographs i. Panoramic radiographs ii. TMJ radiographs iii. Cephalograms 2. Based on importance in diagnosis a. Essential diagnostic radiographs i. IOPA radiographs ii. Bitewing radiographs iii. Panoramic radiographs b. Supplementary diagnostic radiographs i. Occlusal radiographs ii. Cephalometric radiographs iii. Hand–wrist radiographs iv. TMJ radiographs. Q. 7. Head types or facial types Or Panoramic radiograph Ans. The orthopantomogram (OPG) is a radiographic procedure used to record a single image that covers major part of facial region. The maxillary and mandibular arches and their supporting structures are all visualized in a single film. Uses Used for evaluation of dental development in the mixed dentition. To locate supernumerary tooth or congenitally missing tooth or impacted tooth. To detect presence of impactions, pathologic lesions and diagnosis of jaw bone fractures. Advantages The amount of radiation exposure to the patient is low. Highly valuable as an initial survey radiograph. Useful in patients with extreme gag reflex and those with trismus. Disadvantages The image is not as clear as periapical films. Radiopaque shadows are formed by structures like earrings, ramus of mandible, spinal cord, etc. It requires very expensive equipment. Ans. Head type is determined based on the anthropometric determination of maximum skull width and maximum skull length. Head types are classified as follows: i. Mesocephalic: Average-shaped head ii. Brachycephalic: Broad and round head iii. Dolichocephalic: Long and narrow head. Q. 8. Path of closure Ans. The path of closure of mandible from the postural rest position to maximum intercuspation is evaluated in sagittal, vertical and transverse planes. Patient is examined for presence of functional shifts in the anterior, posterior or lateral direction. Examples: i. Upwards and forwards—normal ii. Upwards and backwards—class II division 2 iii. Upward forward and forward—pseudo class III and anterior crossbites. Q. 9. Electromyograms Or Electromyogram as diagnostic aid Q. 6. Classify X-rays in orthodontics Ans. Radiographs used in orthodontics are classified as follows: Orthodontics-Part-I-2013.indd 97 Ans. The procedure that is used for recording the electrical activity of the muscles when they are excited is known as 12/3/2013 2:49:16 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 98 electromyography (EMG). The instrument used is called electromyograph and the output is called electromyogram. The electromyograph is a machine used to receive, amplify and record the action potential during muscle activity. Permanent paper record is obtained with a pen writing device. Electromyogram can be displayed on an oscilloscope. Uses Used to study the role of musculature in craniofacial growth. EMG is used to assess the aberrant muscular activity associated with various habits. Abnormal muscle activity associated with certain forms of malocclusion can be detected with the help of EMG. Examples: i. Abnormal buccinator activity in class II division 1. ii. The hypofunctional upper lip in severe class II division 1 malocclusion. Q. 10. Intraoral periapical radiograph—uses Ans. Intraoral periapical (IOPA) radiographs are most commonly used radiographs in dentistry to visualize the teeth and the supporting alveolar bone. These are indicated when there is a major discrepancy between the dental age and the chronological age of the patient for determination of skeletal maturity status. Serial assessment of skeletal age is used in studying growth of an individual. It is a valuable aid in research aimed at studying the effect of heredity, environment, nutrition, etc. on the skeletal maturation pattern. Q. 12. Cephalometric radiography Ans. ‘Cephalo’ means head and ‘metric’ means measurement. The measurement of the head from the shadows of the bony and soft tissue landmark on the radiographic image is known as roentgenographic cephalometry. These are specialized radiographs of skull in which the head is positioned in a specially designed head holder called cephalostat. Thus, it is a standardized technique where in the head is held in a predetermined position. Cephalograms are also used for longitudinal studies, i.e. comparison of serial radiographs. Cephalometric radiographs are of two types: i. Lateral cephalogram ii. Posteroanterior cephalogram. Uses of IOPA radiographs are as follows: i. To examine the amount of demineralization in carious tooth. ii. To study the extent of root resorption and root formation in the deciduous and permanent teeth, respectively. iii. To visualize the root for any fractures or external resorption or periapical pathology. iv. To view the size, location and angulation of impacted teeth. v. To confirm the congenital absence of teeth or presence of supernumerary tooth. Q. 13. Facial forms Q. 11. Hand–wrist X-rays Ans. Or Hand–wrist radiographs Ans. The hand–wrist radiographs are commonly used among the various skeletal maturity indicators in orthodontics. The numerous small bones in the hand–wrist region show a predictable and scheduled pattern of appearance, ossification and union from birth to maturity. Thus, by comparing patient’s hand–wrist radiograph with a standard radiographs that represent different skeletal ages, the skeletal maturation status of the individual can be determined. Orthodontics-Part-I-2013.indd 98 Ans. Facial form is estimated by dividing morphological facial height by bizygomatic width. Various facial forms are as follows: i. Mesoprosopic: Average facial form ii. Euryprosopic: Broad and short facial form iii. Leptoprosopic: Long and narrow facial form. Q. 14. Bitewing radiographs Bitewing radiographs give information about the tooth and the supporting alveolar bone up to half the length of the root. Uses of bitewing radiographs are as follows: They are used for detecting: Interproximal caries at an early stage and secondary caries under restorations. Bone loss at the alveolar crest. Calculus deposits and overhangs in the restoration at the interproximal areas. Occlusal pattern. Q. 15. Kesling setup 12/3/2013 2:49:16 PM
  • Topic wise Solved Questions of Previous Years 99 Ans. The diagnostic setup was first proposed by HD Kesling. The Kesling diagnostic set-up is made from an extra set of trimmed and polished study models. The cast is cut using a fretsaw blade to separate the individual teeth. A horizontal cut is made 3 mm apical to the gingival margin. Vertical cuts are made to separate the individual teeth. The individual teeth and their associated alveolar processes are sectioned off and replaced on the model base in the desired positions using red wax. Uses of diagnostic setup It helps in simulating the various tooth movements that are planned for patients. The patients can be motivated by simulating the various corrective procedures on the cast. Tooth size: Arch length discrepancies can be visualized by means of a set-up. Q. 16. Carpal bones Ans. Carpal bones were first named by Lyser in 1683. Each hand–wrist area has 8 carpals, 5 metacarpals and 14 phalanges. The carpal bones are arranged in two rows: i. Distal row: Trapezium, trapezoid, capitate, hamate ii. Proximal row: Scaphoid, lunate, triquetral, pisiform. These small irregular bones lie in between the long bones of forearm and the metacarpals. Q. 17. Gnathostatic models active contraction of the perioral and mentalis muscles. Potentially incompetent lips are the normal lips that fail to form a lip seal due to proclined upper incisors. Q. 19. Facial profile Ans. The facial profile is examined by viewing the patient from the side. The facial profile is assessed by joining the two reference lines: i. A line joining the forehead and the soft tissue point A ii. A line joining point A and the soft tissue pogonion. Three types of profiles exist based on the relationship between these two lines: i. Straight profile: The lines form a straight line. ii. Convex profile: The lines form an angle that is pointed away from the face, e.g. class II skeletal pattern. iii. Concave profile: The lines form an angle that is pointed towards the face, e.g. class III skeletal pattern. The facial profile helps in diagnosing gross deviations in the maxillomandibular relationship. Q. 20. Evaluation of smile Ans. One of the important aspects of orthodontic treatment is creation of pleasing smile. Evaluation of smile Smile is evaluated by its vertical, transverse and oblique characteristics. Vertical characteristics Ans. Gnathostatic models are orthodontic study models where the base of the maxillary cast is trimmed to correspond to the Frankfurt horizontal plane. Q. 18. Incompetent lips Ans. Competency of lips can be defined as the ability to approximate the lips without any strain. Lips that are in slight contact when the musculature is relaxed and 2 mm of incisal edges of upper incisors showing at rest is considered normal competent lips. Anatomically lips that do not contact each other when the musculature is relaxed are known as incompetent lips. These are morphologically short lips this do not form a lip seal in a relaxed state. The lip seal can only be achieved by Orthodontics-Part-I-2013.indd 99 Incisor display and gingival display are two main features of vertical characteristics of smile. Inadequate incisor display can be due to vertical maxillary deficiency, restricted lip mobility and short clinical crown. Gummy smile will be associated with vertical maxillary excess. Transverse characteristics There are three important features: (i) buccal corridor width, (ii) arch form and (iii) transverse cant. Buccal corridor width Buccal corridor is represented by a ratio of intercommissure width divided by the distance from one maxillary first premolar to opposite side first premolar. Excessively wide buccal corridor is referred to as negative space. 12/3/2013 2:49:16 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 100 Arch form Arch form plays an important role in the form of smile. In patients with collapsed arch or narrow maxilla, smile also is narrow. Transverse cant Asymmetric vertical growth of the arches or differential eruption of teeth can cause appearance of transverse cant or tilt of the smile line. Ideally there should not be any transverse cant. Oblique characteristics Maxillary occlusal plane from premolar to premolar should be in consonant with the curvature of the lower lip on smile. Downward tilt of the posterior maxilla or upward tilt of anterior maxilla can result in deviation. iii. Straight or orthognathic: The line between the forehead and chin is straight or perpendicular to the floor. Example: class I cases. Q. 22. Lateral cephalogram Ans. The measurement of the head from the shadows of the bony and soft tissue landmarks on the radiographic image is known as roentgenographic cephalometry. Cephalometric radiographs are of two types: i. Lateral cephalogram ii. Posteroanterior cephalogram. Lateral cephalogram: This provides a lateral view of the skull. It is taken with the head in a standardized reproducible position at a specified distance from the source of the X-ray. Q. 21. Facial divergence Q. 23. Sheldon body type Ans. Facial divergence is defined as inclination of lower face relative to forehead. It is influenced to a large extent by the patient’s ethnic and racial background. Facial divergence can be of following three types: i. Anterior divergent: A line drawn between the forehead and chin is inclined anteriorly towards the chin. Example: class III cases. ii. Posterior divergent: A line drawn between the forehead and chin slants posteriorly towards chin. Example: class II cases. Topic Ans. Sheldon’s classification of body type or build-up is as follows: i. Ectomorphic: Tall and thin—body tissue is made of primarily skin and neural elements. ii. Mesomorphic: Average—body tissue is made of primarily mesodermal tissue (muscular and robust individuals). iii. Endomorphic: Short and obese—body tissue is made of primarily fat tissues. 11 CEPHALOMETRICS LONG ESSAYS Q. 1. Discuss cephalometrics as a diagnostic aid. Or Classify diagnostic aids. Discuss the uses of cephalometrics. Or Orthodontics-Part-I-2013.indd 100 Classify the diagnostic aids. Define cephalometric landmarks and planes. Ans. Diagnostic aids are means by which a comprehensive database of pertinent information is derived. The orthodontic diagnostic aids are of two types, namely: 12/3/2013 2:49:16 PM
  • Topic wise Solved Questions of Previous Years 101 I. Essential diagnostic aids For example: i. Case history ii. Clinical examination iii. Study models iv. Certain radiographs a. IOPA b. Bitewing c. OPG v. Facial photographs II. Non-essential diagnostic aids or supplemental diagnostic aids For example: i. Supplemental radiographs a. Occlusal films b. Lateral jaw views c. Cephalometric radiographs ii. EMG iii. Hand–wrist radiographs iv. Endocrine lists v. Estimation of BMR vi. Diagnostic set-up vii. Occlusograms Holly Broadbent (USA) and Herbert Hofrath (Germany) simultaneously presented a standardized cephalometric technique in 1931. Cephalometrics is used to describe the analysis and measurements made on the cephalometric radiographs. Cephalograms are of two types: i. Lateral cephalogram (lateral view of skull) ii. Frontal cephalogram (AP view of skull) Uses of Cephalometrics Cephalometrics is a valuable tool in treatment planning and follow-up of orthodontic patients. Cephalometrics helps in: i. Orthodontic diagnosis (by studying skeletal and dental, and supporting structures) ii. Classification of facial type (skeletal and dental) iii. Treatment planning iv. Evaluation of treatment results v. Prediction of growth-related changes and changes associated with surgical treatment vi. Research works involving cranio-dento-facial region. Technical Aspects of Cephalometrics The standard apparatus used to take cephalograms consists of (Fig. 11.1): i. An X-ray source ii. A cephalostat (head-holding device) iii. A cassette holder. Cephalostat stabilizes the head of the patient with the help of ear rods, orbital pointer and forehead clamp. The distance between the X-ray source and midsagittal plane of the patient is fixed at 5 feet. Cephalometric Landmarks Certain landmarks or points on the skull are used by cephalometrics for quantitative analysis and measurements. The landmarks used in cephalometrics should be easily visible on radiographs, uniform in outline and easily reproducible, permitting valid quantitative measurements of lines and angles projected from them. Cephalometric landmarks are: I. Anatomic landmarks: Represent actual anatomic structures of skull. Derived landmarks: They are obtained secondarily from anatomic structures. Hard-tissue landmarks II. Soft-tissue landmarks Some of the important points and landmarks described in lateral cephalometric projection are (Fig. 11.2) as follows: Unilateral landmarks (Fig. 11.2) Bilateral landmarks i. ii. iii. iv. v. vi. vii. viii. ix. x. xi. xii. xiii. xiv. i. ii. iii. iv. v. vi. vii. viii. ix. x. xi. Sella Nasion Anterior nasal spine (ANS) Posterior nasal spine (PNS) Point A Point B Basion Gnathion Menton Prosthion Infradentale PTM point Subnasal Glabella Orbital Porion Bolton point Gonion Pogonion Articulare Condylion The key ridge Broadbent registration point Glabella Chelion N S P O Ar Bo PTM PNS Ba ANS A Go B Pog Me Fig. 11.1 A standard cephalometric arrangement. Orthodontics-Part-I-2013.indd 101 Gn Fig. 11.2 Lateral cephalometric landmarks. 12/3/2013 2:49:16 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 102 The definitions of each of the above points or landmarks used in cephalometric are as follows: Unilateral landmarks (Fig. 11.2) i. Sella: The point representing the midpoint of the pituitary fossa or sella turcica. ii. Nasion: The intersection of internasal suture with the nasofrontal suture in the midsagittal plane. iii. Anterior nasal spine (ANS): It is the tip of the anterior nasal spine seen on the X-ray film from norma lateralis. iv. Posterior nasal spine (PNS): It is the tip of the posterior spine of the palatine bone in the hard palate. v. Point A (subspinale): It is the deepest point in the midline between the anterior nasal spine and (alveolar crest between two central incisors) prosthion. vi. Point B (supramentale): It is the deepest point in the midline between the alveolar crest of mandible and the mental process. vii. Basion: The lowermost point on the anterior margin of the foramen magnum in the midsagittal plane. viii. Gnathion: The most anteroinferior point in the contour of the chin. ix. Menton: The lowermost point on the mandibular symphysis. x. Prosthion (Supradentale): The lowest and most anterior point on the alveolar bone in the midline between the upper central incisors. xi. Infradentale: The highest and most anterior point on the alveolar process in the median plane between mandibular central incisors. xii. Ptm point: It is the intersection of the inferior border of the foramen rotundum with the posterior wall of the pterygomaxillary fissure. xiii. Subnasale: The point where the lowest border of the nose meets the outer contour of the upper lip. xiv. Glabella: It is the most prominent point of the forehead in the midsagittal plane. Bilateral landmarks i. Orbitale: The lowest point on the inferior bony margin of the orbit. ii. Porion: The highest bony point on the upper margin of external auditory meatus. iii. Bolton point: The highest point in the upward curvature of the retrocondylar fossa (Broadbent). iv. Gonion: It is a constructed point at the junction of ramal and mandibular planes. It is most inferiorly, posteriorly and outwardly directed point. v. Pogonion: It is the most anterior point in the contour of the chin. Orthodontics-Part-I-2013.indd 102 vi. Articulare: It is a point at the junction of the posterior border of ramus and the inferior border of the basilar part of the occipital bar. vii. Condylion: The most superior point on the head of the condyle. viii. The key ridge: The lowermost point on the contour of the anterior wall of the infratemporal fossa. ix. Broadbent registration point: It is the midpoint of the perpendicular from the centre of sella turcica to the Bolton plane. x. Glabella: It is the most prominent point of the forehead in the midsagittal plane. xi. Chelion: It is the lateral terminus of the oral slit on the outer corner of the mouth. LINES AND PLANES IN CEPHALOMETRICS These lines and planes are obtained by connecting two landmarks. Based on their orientation, they are classified as horizontal and vertical planes. Horizontal Planes i. ii. iii. iv. v. vi. SN plane Frankfurt horizontal plane Occlusal plane Mandibular plane Basion–nasion plane Bolton plane. i. SN plane (Fig. 11.3) It represents anterior cranial base. It is the cranial line between the sella and nasion. S N Fig. 11.3 SN plane (sella–nasion plane). 12/3/2013 2:49:16 PM
  • Topic wise Solved Questions of Previous Years 103 ii. Frankfurt horizontal plane (Fig. 11.4) This plane connects the orbitale and porion. Go P O M Fig. 11.6 Mandibular plane. v. Basion–nasion plane (Fig. 11.7) Fig. 11.4 Frankfurt horizontal plane. It is a line connecting the basion and nasion and represents cranial base. iii. Occlusal plane (Fig. 11.5) It is a denture plane bisecting the posterior occlusion of permanent molars and premolars, and extends anteriorly. N Ba Fig. 11.5 Occlusal plane. Fig. 11.7 Basion–nasion plane. iv. Mandibular plane (Fig 11.6) vi. Bolton plane According to Down, mandibular plane is a line connecting gonion and menton. It is a plane that connects Bolton point posterior to the occipital condyles and nasion. Orthodontics-Part-I-2013.indd 103 12/3/2013 2:49:16 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 104 Vertical Planes iii. Facial axis (Fig. 11.10) Various commonly used vertical planes in cephalometrics are as follows: i. A-pog line ii. Facial plane iii. Facial axis iv. Aesthetic plane. It is a line from Ptm point to cephalometric gnathion. i. A-pog line (Fig. 11.8) It is a line extending from point A on the maxilla to the pogonion on the mandible. Ptm A Gn Fig. 11.10 Facial axis. Pog iv.‘E’-plane or aesthetic plane (Fig. 11.11) It is a line between the most anterior point of the soft tissue of nose and soft tissue of chin. Fig. 11.8 A-pogonion plane. ii. Facial plane (Fig. 11.9) It is a line from the nasion to pogonion. N Fig. 11.11 Aesthetic plane. With all the above-mentioned standard points and measurable planes and angles, cephalometric aids in skeletal, dental and soft-tissue analysis and classification of various malocclusions. Pog Q. 2. Write about any one cephalometric analysis of your choice used in orthodontics. Fig. 11.9 Facial plane. Orthodontics-Part-I-2013.indd 104 Or 12/3/2013 2:49:17 PM
  • Topic wise Solved Questions of Previous Years 105 What is standardization in cephalometrics? Discuss Steiner’s cephalometric analysis. Or Enumerate cephalometric analysis and elaborate on Steiner’s analysis. N S Ans. Various cephalometric analyses are as follows: 1. Methodological classification a. Angular analyses—SNA, SNB, ANB, Tweed’s analysis b. Linear analyses—McNamara analysis, COGS. A 2. According to area of analysis a. Skeletal analysis—SNA, SNB, ANB b. Dentoalveolar analysis—Upper central incisor to NA c. Soft-tissue analysis—E-plane. STEINER’S ANALYSIS Cecil C Steiner in 1930 developed this analysis. The idea is to provide maximum clinical information with least number of measurements. Fig. 11.12 SNA angle. b. SNB angle (Fig. 11.13) The Steiner’s analysis is divided into three parts: i. Skeletal analysis ii. Dental analysis iii. Soft-tissue analysis. I. Skeletal Analysis The Steiner’s skeletal analysis considers the following parameters: a. SNA angle b. SNB angle c. ANB angle d. Mandibular plane angle e. Occlusal plane angle. The mean values of parameters considered in Steiner’s skeletal analysis are: SNA angle SNB angle ANB angle Mandibular plane angle 80° 2° 32° N S Occlusal plane angle 82° The angle formed between SN plane and line joining nasion and point B. SNB angle indicates anteroposterior positioning of mandible in relation to cranial base. The mean value of SNB angle is 80°. SNB >80°—mandibular retrognathism (class III) SNB <80°—mandibular retrognathism (class II). 14.5° B a. SNA angle (Fig. 11.12) The angle formed between SN plane and the line joining the nasion to point A is SNA angle. It indicates anteroposterior positioning of maxilla in relation to cranial base. The mean value is 82°. SNA >82°—maxillary prognathism SNA <80°—retrognathism of maxilla. Orthodontics-Part-I-2013.indd 105 Fig. 11.13 SNB angle. 12/3/2013 2:49:17 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 106 c. ANB angle (Fig. 11.14) e. Occlusal plane angle (Fig. 11.16) Angle formed by intersection of line joining nasion to point A and nasion to point B is known as ANB angle. ANB angle indicates relative position of maxilla and mandible to each other. The mean value of ANB angle is 2°. ANB >2°—class II tendency ANB <2°—class III relationship. It is the angle formed between occlusal plane and SN plane. It indicates the relation of occlusal plane to cranium and faces the growth pattern of an individual. It has a mean value of 14.5°. ↑Occlusal plane angle—clockwise rotation of occlusal plane. ↓ Occlusal plane angle—counterclockwise rotation of occlusal plane. N S N A B Fig. 11.14 ANB angle. Fig. 11.16 Occlusal plane angle. d. Mandibular plane angle (Fig. 11.15) Mandibular plane angle is the angle between SN plane and mandibular plane (Go–Gn). It indicates the growth pattern of an individual. The average value is 32°. <32° — Suggests horizontally growing face >32° — Suggests vertically growing face. S N II. Dental Analysis The mean values of parameters considered in Steiner’s dental analysis are: Parameter Upper incisor to NA (angle) Upper incisor to NA (linear) Lower incisor to NB (angle) Lower incisor to NB (linear) Interincisal angle Mean value 22° 4 mm 25° 4 mm 131° a. Upper incisor to NA angle (Fig. 11.17) Go Gn Fig. 11.15 Mandibular plane angle. Orthodontics-Part-I-2013.indd 106 It is the angle formed by intersection of the long axis of upper central incisors and the line joining nasion to point A. The mean value is 22°. It indicates relative inclination of the upper incisors. ↑Upper incisor to NA angle—upper incisor proclination, e.g. class II division I. ↓Upper incisor to NA angle—upper incisor retroclination. 12/3/2013 2:49:17 PM
  • Topic wise Solved Questions of Previous Years 107 c. Lower incisor to NB angle (Fig. 11.19) xis ga Lon It is the angle between long axis of lower incisor to the NB line. The mean value is 25°. ↑Value seen in lower incisor proclination. N of NA line A Fig. 11.17 Upper incisor to NA angle. b. Upper incisor to NA linear (Fig. 11.18) It is the lineal measurement between labial surface of central incisor and the line joining nasion to point A. It is the linear measurement between labial surface of central incisor and line joining nasion to point A. This helps to determine upper incisor position. The mean value is 4 mm. ↑Value seen in upper incisor proclination. Figure 11.19 Lower incisor to NB angle. d. Lower incisor to NB linear (Fig. 11.20) It is the linear distance between labial surface of lower central incisor and the line joining nasion to point B. It helps to assess lower incisor inclination. Average value is 4 mm. ↑ Value seen in proclined lower incisors. N B Fig. 11.18 Upper incisor to NA linear. Orthodontics-Part-I-2013.indd 107 Fig. 11.20 Lower incisor to NB linear. 12/3/2013 2:49:17 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 108 e. Interincisal angle (Fig. 11.21) The angle formed between long axis of upper and lower central incisors is known as interincisal angle. Mean value is 130–131°. ↓ Interincisal angle — class II division 1 or class I bimaxillary protrusion. ↑ Interincisal angle — class II division 2 cases. Lips located beyond this line—protrusive (convex profile) Lips located behind this line—retrusive (concave profile). Q. 3. Describe the role of cephalometric radiography in orthodontics. Give various planes and angles used in cephalometric analysis. Or Discuss about clinical implications of growth and development, enumerating the use of cephalometrics to study the same. Ans. Fig. 11.21 Interincisal angle. III. Soft-tissue Analysis According to Steiner in a well-balanced face, lips should touch the line extending from soft tissue contour of chin to midline of an ‘S’ formed by the lower border of nose (Fig. 21.22). S-line Fig. 11.22 S-line. Orthodontics-Part-I-2013.indd 108 The various ways of assessment of growth using cephalometric radiography are as follows: i. Assessment of expected growth ii. Determination of direction of growth iii. Growth time table iv. Assessment of growth rates v. Growth prediction vi. Growth changes associated with treatment vii. Growth following treatment conclusion. i. Assessment of expected growth: In orthodontic treatment planning quantitative assessment of growth is an important part. Biological age is determined chiefly by hand–wrist radiographs. ii. Determination of direction of growth: Cephalometric radiography differentiates between horizontal and vertical growth patterns. Broad mandibular base Horizontal growth Ramus with a thick symphysis Narrow mandible with thin symphysis—vertical growth Frankfurt mandibular angle Less than normal in horizontal growth Go–Gn to SN angle More than normal in vertical growth iii. Growth time table: Timing of growth rates can be assessed from developmental stages and occurrence of growth spurts can be estimated. iv. Assessment of growth rates: Increase in size correlating with growth rates in certain regions like N–mg, S–as, Ar–Gn can be assessed by cephalometrics. v. Growth prediction: Various methods of growth prediction are—Johnston grid method, Holdaway’s prediction, Rickett’s prediction (visual treatment objective). Visual treatment objective (VTO) acts as a blueprint to establish objectives of treatment for a particular pa- 12/3/2013 2:49:18 PM
  • Topic wise Solved Questions of Previous Years 109 tient; it is a visual plan to predict the normal growth of the patient and anticipate the effects of treatment. vi. Growth changes associated with treatment: Rickett’s four-step analysis is used to study growth versus treatment changes. vii. Growth following conclusion of treatment: Growth change that takes place after active treatment can be predicted using cephalograms. Various planes used in cephalometrics These planes are obtained by connecting two landmarks. Based on their orientation these are classified as: horizontal and vertical planes. 1. Horizontal planes i. SN plane ii. Frankfurt horizontal plane iii. Occlusal plane iv. Mandibular plane v. Basion–nasion plane vi. Bolton plane. 2. Vertical planes i. A-pog line ii. Facial plane iii. Facial axis iv. Aesthetic plane. SHORT ESSAYS Q. 1. Uses of cephalometrics Ans. Cephalometry is the measurement of head of a living subject from bony landmarks by palpation. The measurement of the head from the shadows of the bony and soft-tissue landmark on the radiographic image is known as roentgenographic cephalometry. Cephalometrics is a valuable tool in the treatment planning and follow-up of orthodontic patients. Uses of cephalometrics Cephalometrics helps in: i. Orthodontic diagnosis (by studying skeletal, dental and supporting structures) ii. Classification of facial type (skeletal and dental) iii. Treatment planning iv. Evaluation of treatment results v. Prediction of growth-related changes and changes associated with surgical treatment vi. Research works involving cranio–dento–facial region. II. The significance of angles formed from these three planes is as follows: a. Frankfurt mandibular plane angle (FMA): The angle is formed by the Frankfurt horizontal plane with the mandibular plane. The average value is 25°. If FMA is 16–28°—prognosis is good. If FMA 28–35°—prognosis is fair. If FMA is >35°—prognosis is bad. Extractions frequently complicate the problems. b. Incisor mandibular plane angle (IMPA): Angle formed between long axis of lower incisor with mandibular plane. The mean value is 90°. If IMPA>110°—proclined lower incisors. IMPA<85°—retroclined lower incisors. c. Frankfurt mandibular incisor angle (FMIA): Angle formed between long axis of lower incisor and Frankfurt horizontal plane. Mean value is 65°. Tweed’s diagnostic triangle is used in diagnosis, classification, treatment planning as well as for prognosis of orthodontic cases. Q. 2. Tweed’s triangle Ans. The objectives of Tweed’s analysis (Fig. 11.23) are: i. Determination of lower incisor position ii. Evaluation of prognosis of a case. I. The planes used in Tweed’s analysis that form a diagnostic triangle are: Frankfurt horizontal plane Mandibular plane Long axis of lower incisor. Orthodontics-Part-I-2013.indd 109 FH plane FMA Ma nd ibu FMA lar pla ne PA IM Long axis of lower central incisor Fig. 11.23 Tweed’s analysis. 12/3/2013 2:49:18 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 110 Q. 3. Down’s analysis Or Write the skeletal measurements of Down’s analysis. Ans. Down’s analysis is one of the most frequently used cephalometric analysis, which measures the skeletal and dental pattern of the patients to define the underlying facial type and establish the relation of dentition to the underlying bony structures. Down’s analysis consist of following skeletal and dental parameters (five each): Skeletal parameters i. Cant of occlusal plane ii. Interincisal angle iii. Incisor mandibular plane angle v. Y-axis (growth axis) vi. Upper incisor to A-pog N (N–A Line) Nasion to point lin e Dental parameters i. ii. iii. iv. v. This angle reveals the convexity or concavity of the skeletal profile. Average value is 0° with the range of – 8.5 to 10°. ❍ Positive or ↑ angle of convexity—prominent maxillary denture base relative to mandible ❍ Negative or ↓ angle of convexity—prognathic profile. Facial angle Angle of convexity A–B plane angle Mandibular plane angle Incisor mandibular plane angle A Point A to Pogonion line (A-Pog line) Pog Skeletal Parameters Fig. 11.25 Angle of convexity. i. Facial angle (Fig. 11.24) Facial angle is the inside inferior angle formed by the intersection of the FH plane and nasion–pogonion plane. This angle indicated anteroposterior positioning of the mandible in relation to the upper face. The average value is 87.8° with the range of 82–95°. ↑ Facial angle — skeletal class III with prominent chin ↓ Facial angle — skeletal class II. iii. A–B plane angle (Fig. 11.26) N P FH pla ne N A O Nasion–pogonion plane Pog Fig. 11.24 Facial angle. ii. Angle of convexity (Fig. 11.25) Angle of convexity is formed by intersection of a line from nasion to point A and a line from point A to pogonion. Orthodontics-Part-I-2013.indd 110 B Pog Fig. 11.26 A–B plane angle. A–B plane angle is formed between a line connecting point A to point B and N-pog line. This angle is indicative of maxillomandibular relationship in relation to facial plane. Mean value is −4.6° with a range of −9° to 0°. Usually A–B plane angle is negative. In class III cases, A–B plane angle is positive. 12/3/2013 2:49:18 PM
  • Topic wise Solved Questions of Previous Years 111 iv. Mandibular plane angle (Fig. 11.27) Mandibular plane angle is formed between FH plane and mandibular plane. Mean value is 21.9° with range of 17° to 28°. ↑ Mandibular plane angle suggests vertical growth with hyperdivergent facial pattern. FH plane P Dental parameters i. Cant of occlusal plane (Fig. 11.29) This angle is formed between the occlusal plane and Frankfurt horizontal plane. This angle gives a measure of the slope of occlusal plane relative to the FH plane. Mean value is 9.3° with range of 1.5–14°. ❍ ↑ Cant of occlusal plane seen in class II cases (short ramus). ❍ ↓ Cant of occlusal plane seen in long mandibular ramus. O P Ma ndi bul ar p FH plane O lan e Fig. 11.27 Mandibular plane angle. Occlu sal pla ne v. Y-axis/growth axis (Fig. 11.28) Y-axis or growth axis is an acute angle formed by the intersection of Frankfurt horizontal plane with a line from sella turcica to gnathion. Y-axis indicates that the growth pattern of the individual mean value is 59.4° with range of 53–66°. Y-axis > normal—indicates greater vertical growth of mandible. Y-axis < normal—indicates greater horizontal growth of mandible. This angle is greater in class II than class III facial patterns. Fig. 11.28 Y-axis (growth axis). Orthodontics-Part-I-2013.indd 111 Fig. 11.29 Cant of occlusal plane. ii. Interincisal angle (Fig. 11.30) The angle formed between the long axes of the upper and lower incisors is known as interincisal angle. The average is 135.4° with a range of 130–150.5°. ❍ ↓ Interincisal angle—class I bimaxillary protrusion and class II division 1 cases. ❍ ↑ Interincisal angle—class II division 2 cases. Fig. 11.30 Interincisal angle. 12/3/2013 2:49:18 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 112 iii. Incisor occlusal plane angle (Fig. 11.31) It is an inside inferior angle formed by the intersection of the long axis of lower central incisor and the occlusal plane. The average value is 14.5° with range of 3.5–20o. It is read as a plus or minus deviation from a right angle. ↑ Incisor occlusal plane angle suggests lower incisal proclination. Average value is 2.7 mm with range of 1–5 mm. The measurement is more in patients with upper incisor proclination. Upper incisor Pog Occlu sal pla ne Fig. 11.33 Upper incisor to A-pog line. Long axis of lower central incisor Fig. 11.31 Incisor occlusal plane angle. iv. Incisor mandibular plane angle (Fig. 11.32) This angle is formed by intersection of long axis of lower incisor and mandibular plane. Mean value is 1.4° with a range of –8.5° to 7°. ↑ incisor mandibular plane angle—lower incisor proclination. Long axis of incisor Q. 4. Enumerate five horizontal planes used in cephalometrics and give their uses and significance. Ans. In cephlalometrics, various lines and planes are obtained by connecting two landmarks. Based on their orientation, they are classified as horizontal and vertical planes. Horizontal planes are as follows: i. SN plane ii. Frankfurt horizontal plane iii. Occlusal plane iv. Mandibular plane v. Basion–nasion plane. i. SN plane (Fig. 11.3) It represents anterior cranial base. It is the cranial line between the sella and nasion. ii. Frankfurt horizontal plane (Fig. 11.4) This plane connects the orbitale and porion. Ma iii. Occlusal plane (Fig. 11.5) ndi bul ar p lan e It is a denture plane bisecting the posterior occlusion of permanent molars and premolars, and extends anteriorly. It is a denture plane bisecting the posterior occlusion of permanent molars and premolars, and extends anteriorly. iv. Mandibular plane (Fig. 11.6) Fig. 11.32 Incisor mandibular plane angle. v. Upper incisor to A-pog line (Fig. 11.33) Upper incisor to A-pog line or protrusion of maxillary incisors is a linear measurement between the incisal edge of maxillary central incisor and line joining point A to pogonion. Orthodontics-Part-I-2013.indd 112 According to Down, mandibular plane is a line connecting gonion and menton. v. Basion–nasion plane (Fig. 11.7) It is a line connecting the basion and nasion, and represents cranial base. Q. 5. What is conventional cephalometrics? Give its drawbacks. 12/3/2013 2:49:18 PM
  • Topic wise Solved Questions of Previous Years 113 Ans. Cephalogram is a cephalometric radiography introduced to orthodontics by Holly Broadbent and Herbert Hofrath in 1931. It is used in orthodontics to elucidate the skeletal, dental and soft-tissue relationships. Limitations of cephalogram are as follows: i. Exposure of patient to harmful ionizing radiation. ii. A serious disadvantage is the absence of anatomical references, which remain constant with time. iii. The process of image acquisition as well as measurement procedures is not well standardized. iv. The structures being imaged are three-dimensional whereas the radiographic image is two-dimensional. v. Anatomical structures lying at different planes within the head undergo projective displacement. vi. Some reference landmarks and planes do not agree with anatomical landmarks. vii. There could be a mandibular shift from centric relation as the patient is made to bite in maximum intercuspation. viii. The cephalometrics makes use of means obtained from different population samples; hence it has only limited relevance when applied to individual patient. ix. The composite of lines and angles used in cephalometric analysis yields limited information about patient’s dentoskeletal patterns. x. Solely based on cephalometric analysis, orthodontic diagnosis cannot be made. Q. 6. Visual treatment objective (VTO) Ans. Visual treatment objective (VTO) is of two types: a. Clinical VTO b. Cephalometric VTO. a. Clinical VTO i. Creekmore advocated clinical VTO as an aid to decide the type of appliance in skeletal class II malocclusion. ii. This procedure consists of asking the patient to bring the mandible to an edge-to-edge bite relation and note the change in appearance of the patient at two levels— one at edge-to-edge and the other at a position midway between existing occlusion and edge-to-edge position. iii. If the profile worsens at the edge-to-edge position, fault lies in maxilla; and to correct maxillary prognathism appliances like maxillary intrusion splint or headgears are advised. iv. If the profile improves at the edge-to-edge position, it indicates fault in mandible. Then functional appliances that stimulate the growth of mandible are indicated. v. If the profile improves at midway position; it is a combined case of fault—both in maxilla and mandible, and Orthodontics-Part-I-2013.indd 113 hence appliances like activator, headgear, twin block with headgears are indicated. b. Cephalometric VTO It is like a blueprint or a visual plan to predict the normal growth of the patient and the anticipated effects of the treatment to establish the objectives of treatment for an individual patient. VTO permits development of alternative treatment plans and to set the goals in advance for the treatment. Q. 7. Steiner’s skeletal analysis Ans. Steiner’s analysis Cecil C. Steiner in 1930 developed this analysis. The idea is to provide maximum clinical information with least number of measurements. The Steiner’s analysis is divided into three parts: i. Skeletal analysis ii. Dental analysis iii. Soft-tissue analysis. i. Skeletal Analysis The Steiner’s skeletal analysis considers the following parameters: a. SNA angle b. SNB angle c. ANB angle d. Mandibular plane angle e. Occlusal plane angle. The mean values of parameters considered in Steiner’s skeletal analysis are: SNA angle SNB angle ANB angle Mandibular plane angle Occlusal plane angle 82° 80° 2° 32° 14.5° a. SNA angle (Fig. 11.12) The angle formed between SN plane and line joining nasion to point A is SNA angle. It indicates anteroposterior positioning of maxilla in relation to cranial base. The mean value is 82°. SNA>82°—maxillary prognathism. SNA <80°—retrognathism of maxilla. b. SNB angle (Fig. 11.13) The angle formed between SN plane and line joining nasion and point B. SNB angle indicates anteroposterior positioning of mandible in relation to cranial base. The mean value of SNB angle is 80°. 12/3/2013 2:49:19 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 114 ❍ ❍ SNB >80°—mandibular retrognathism (class III). SNB <80°—mandibular retrognathism (class II). c. ANB angle (Fig. 11.14) Angle formed by intersection of line joining nasion to point A and nasion to point B is known as ANB angle. ANB angle indicates relative position of maxilla and mandible to each other. The mean value of ANB angle is 2°. ANB >2°—class II tendency. ANB <2°—class III relationship. d. Mandibular plane angle (Fig. 11.15) Mandibular plane angle is angle between SN plane and mandibular plane (Go–Gn). It indicates the growth pattern of an individual. Average value is 32°. <32°—suggests horizontally growing face. >32°—suggests vertically growing face. e. Occlusal plane angle (Fig. 11.16) It is the angle formed between occlusal plane and SN plane. It indicates the relation of occlusal plane to cranium and faces the growth pattern of an individual. It has a mean value of 14.5°. ❍ ↑ Occlusal plane angle—clockwise rotation of occlusal plane. ❍ ↓ Occlusal plane angle—counterclockwise rotation of occlusal plane. SHORT NOTES Q. 1. Y-axis Ans. Y-axis (growth axis) is considered as one of the skeletal parameters in Down’s analysis (Fig. 11.34). S N Y-axis < normal—indicates greater horizontal growth of mandible. This angle is greater in class II than class III facial patterns. During orthodontic treatment: ❍ Increase in Y-axis suggests—vertical growth pattern or open bite. ❍ Decrease in Y-axis suggests—horizontal growth pattern or deepening of bite. Q. 2. Key ridge Ans. Y-axis FH plane Gn Fig. 11.34 Y-axis (growth axis). Key ridge is the lowermost point on the contour of the anterior wall of the infratemporal fossa. It is the inferiormost point of the anterior border of zygoma, as seen in lateral cephalogram. In his concept of normal occlusion, Angle related maxillary first molar to key ridge position; normally the mesiobuccal root of maxillary permanent first molar is in line with the key ridge. Q. 3. Limitations of cephalogram Ans. Y-axis or growth axis is an acute angle formed by the intersection of Frankfurt horizontal plane with a line from sella turcica to gnathion. Y-axis indicates the growth pattern of the individual. Mean value is 59.4° with range of 53–66°. Y-axis > normal—indicates greater vertical growth of mandible. Orthodontics-Part-I-2013.indd 114 Cephalogram is a cephalometric radiography introduced to orthodontics by Holly Broadbent and Herbert Hofrath in 1931. It is used in orthodontics to elucidate the skeletal, dental and soft-tissue relationships. Limitations of cephalogram are as follows: 12/3/2013 2:49:19 PM
  • Topic wise Solved Questions of Previous Years 115 i. Exposure of the patient to harmful ionizing radiation. ii. A serious disadvantage is the absence of anatomical references, which remain constant with time. iii. The process of image acquisition as well as measurement procedures is not well standardized. iv. The structures being imaged are three-dimensional whereas the radiographic image is two-dimensional. So anatomical structures lying at different planes within the head undergoes projective displacement. v. The cephalometrics makes use of means obtained from different population samples; hence it has only limited relevance when applied to an individual patient. The average is 135.4° with a range of 130–150.5°. ❍ ↓ Interincisal angle—class I bimaxillary protrusion and class II division 1 cases. ❍ ↑ Interincisal angle—class II division 2 cases. Q. 6. S-N plane Ans. S-N plane (Fig. 11.36) represents the anterior cranial base. It is a horizontal cephalometric plane between the centre of sella turcica (S) and the most anterior point of the frontonasal suture (N), i.e. nasion. Q. 4. Enumerate horizontal planes in cephalometry. Ans. In cephlalometrics, various lines and planes are obtained by connecting two landmarks. Based on their orientation these are classified as horizontal and vertical planes. Various horizontal planes are as follows: i. SN plane ii. Frankfurt horizontal plane iii. Occlusal plane iv. Mandibular plane v. Basion–nasion plane. S Fig. 11.36 Sella–nasion (SN) plane. Q. 5. Interincisal angle Ans. N Q. 7. ANB angle Interincisal angle (Fig. 11.35) is one of the variables used in Down’s analysis to measure dental pattern. Or Significance of ANB angle Ans. ANB angle (Fig. 11.14) is one of the parameters used in Steiner’s skeletal analysis. Angle formed by intersection of line joining nasion to point A and nasion to point B is known as ANB angle. ANB angle indicates relative position of maxilla and mandible to each other. The mean value of ANB angle is 2°. ❍ ANB >2°—class II tendency. ❍ ANB <2°—class III relationship. Q. 8. FMA angle Ans. Fig. 11.35 Interincisal angle. The angle formed between the long axes of the upper and lower incisors is known as interincisal angle. Orthodontics-Part-I-2013.indd 115 FMA (Fig. 11.37) is an angle formed by the intersection of the Frankfurt horizontal plane with the mandibular plane. Mean value of FMA is 25°. The Tweed’s analysis makes use of FMA angle in a diagnostic triangle to determine the position of lower incisor and evaluation of prognosis of a case. 12/3/2013 2:49:19 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 116 FMA FMIA In 1931, a standardized cephalometric technique was simultaneously presented by Holly Broadbent (USA) and Herbert Hofrath (Germany). Cephalometrics helps in: ❍ Orthodontic diagnosis ❍ Classification ❍ Treatment planning ❍ Evaluation of treatment results. Hence, it forms a valuable tool in the treatment planning and follow-up of orthodontic patients. IMPA Q. 11. Tweed’s diagnostic triangle Fig. 11.37 Tweed’s diagnostic triangle showing FMA angle. Or Q. 9. SNA angle Tweed’s triangle Ans. Ans. SNA (Fig. 11.38) angle is one of the parameters of Steiner’s skeletal analysis. The Tweed’s diagnostic triangle (Fig. 11.23) is used in diagnosis, classification, treatment planning as well as for prognosis of orthodontic cases. The significance of angles formed from the three planes, i.e. Frankfurt horizontal plane, mandibular plane and long axis of lower incisor that forms three sides of the diagnostic triangle is as follows: i. Frankfurt mandibular plane angle (FMA): The angle formed by the Frankfurt horizontal plane with the mandibular plane. The average value is 25°. If FMA is 16–28°, prognosis is good; if FMA is 28–35°, prognosis is fair; if FMA is >35°, prognosis is bad. Extractions frequently complicate the problems. ii. Incisor mandibular plane angle (IMPA): Angle formed between long axis of lower incisor with mandibular plane. Mean value is 90°; if IMPA >110°, proclined lower incisors; if IMPA<85°, retroclined lower incisors. iii. Frankfurt mandibular incisor angle (FMIA): Angle formed between long axis of lower incisor and Frankfurt horizontal plane. Mean value is 65°. N S A Fig. 11.38 SNA angle. SNA angle is formed by intersection of SN plane and a line joining nasion to point A. It indicates anteroposterior positioning of maxilla in relation to the anterior cranial base. Mean value is 82°. ❍ If SNA>82°—class II (prognathic maxilla). ❍ If SNA < 82°—class III (retrognathic maxilla). Q. 10. Two uses of cephalometrics in orthodontia Or Uses of cephalometrics Ans. Cephalometrics is a non-essential or supplemental diagnostic aid in orthodontic diagnosis. Orthodontics-Part-I-2013.indd 116 Q. 12. Occlusal plane angle Or Occlusal plane Ans. Occlusal plane (Fig. 11.5) is a denture plane bisecting the posterior occlusion of permanent molars and premolars, and extends anteriorly. Significance The angle formed between occlusal plane and SN plane is known as occlusal plane angle. It indicates the relation of occlusal plane to cranium and face, i.e. the growth pattern of an individual. 12/3/2013 2:49:19 PM
  • Topic wise Solved Questions of Previous Years 117 It has a mean value of 14.5° ❍ ↑ Occlusal plane angle—clockwise rotation of occlusal plane. ❍ ↓ Occlusal plane angle—counterclockwise rotation of occlusal plane. Q. 13. Steiner’s soft–tissue analyses Ans. Cecil C Steiner in 1930 developed a cephalometric analysis. The idea is to provide maximum clinical information with least number of measurements. The Steiner’s analysis consisted of three parts, namely, skeletal analysis, dental analysis and soft-tissue analysis. Steiner’s soft-tissue analysis: According to Steiner in a well-balanced face the lips should touch the line extending from soft–tissue contour of chin to midline of an ‘S’ formed by the lower border of nose (Fig. 11.22). ❍ Lips located beyond this line—protrusive (convex profile). ❍ Lips located behind this line—retrusive (concave profile). It determines the position of lower part of the face relative to the forehead using soft-tissue landmarks, i.e. soft tissue nasion and pogonion. Based on a line drawn between the forehead and chin in the natural head position, the facial divergence is of following types: i. Posterior divergent face: When the line is inclined posteriorly in the chin region it is known as posterior divergent face, as seen in class II cases. ii. Straight or orthognathic face: When the line is perpendicular to the floor it is known as straight or orthognathic face, as seen in class I cases. iii. Anterior divergent face: When the line is inclined anteriorly in the chin region it is known as anterior divergent face, as seen in class III cases. Q. 16. Angle SNB Ans. SNB angle (Fig. 11.40) is one of the skeletal parameters considered in Steiner’s analysis. Q. 14. Registration point Ans. The Broadbent registration point (R point) is the midpoint of the perpendicular from the centre of sella turcica to the Bolton–nasion plane (Fig. 11.39). N S N S R Bo Ba B Broadbent Fig. 11.39 Registration point. Q. 15. Facial divergence Ans. Facial divergence was described by Milo Hellmann as the inclination of lower face relative to forehead. Orthodontics-Part-I-2013.indd 117 Fig. 11.40 SNB angle. The angle formed between SN plane and line joining nasion and point B. SNB angle indicates anteroposterior positioning of mandible in relation to cranial base. The mean value of SNB angle is 80°. ❍ SNB> 80°—mandibular retrognathism (class III) ❍ SNB < 80°—mandibular retrognathism (class II). 12/3/2013 2:49:19 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 118 Q. 17. Mandibular plane angle Or Mandibular plane. Ans. Bo Mandibular plane angle (Fig. 11.41) is one of the parameters used in Steiner’s skeletal analysis. Ao SN plane S N Mandibular plane angle Fig. 11.42 Wits appraisal. Go Ma nd ibu lar pla ne Ga Fig. 11.41 Mandibular plane angle. Mandibular plane angle is formed between SN plane and mandibular plane. This angle gives an indication of the growth pattern of an individual. The average value is 32°. ❍ A lower angle indicates—horizontal growing face. ❍ An increased angle indicates—vertical growing face. A functional occlusal plane is drawn and perpendiculars are dropped from points A and B on to it. The points of contact of these perpendiculars on the occlusal plane are termed as AO and BO. The distance between AO and BO gives the anteroposterior relation between the maxilla and mandible. Usually in males—point BO is ahead of AO by 1 mm. In females—the points AO and BO coincide. ❍ In skeletal class II tendency—point BO is behind AO (positive reading). ❍ In skeletal class III pattern—point BO is located ahead of AO (negative reading). The Wits appraisal is mainly used in cases where the ANB angle is considered unreliable due to abnormal position of nasion and rotation of jaws. Q. 20. Frankfurt horizontal plane Q. 18. Cephalostat Ans. Cephalostat is the head holder device—one of the components of standard apparatus used to take cephalograms. A cephalostat consists of ear rods, orbital pointer and forehead clamp to stabilize the head of the patient and position it in three dimensions to receive the X-ray beam. It positions the patient’s head so that distance between the X-ray source and midsagittal plane of the patient is at a fixed distance of 5 feet. Ans. Frankfurt horizontal plane (Fig. 11.4) is a horizontal plane connecting the orbitale and porion. It is one of the cephalometric planes used in the Down’s analysis. It is used as a reference plane in measuring both skeletal and dental patterns of the patient. Q. 21. Define cephalometric points: (i) Point S and (ii) Point Me. Ans. Q. 19. The Wits appraisal Ans. The Wits appraisal (Fig. 11.42) is a measure of the maxillomandibular relation in the anteroposterior or sagittal plane. Orthodontics-Part-I-2013.indd 118 i. Point S: The point representing the midpoint of the pituitary fossa or sella turcica is known as point S. ii. Point Me: It is the inferiormost point in the contour of the chin. 12/3/2013 2:49:19 PM
  • Topic wise Solved Questions of Previous Years 119 Q. 22. ‘E’ plane or aesthetic plane iv. Quick ceph image v. Digigraph. Ans. ‘E’ plane or aesthetic plane (Fig. 11.11) is a line between the most anterior point of the soft tissue of nose and soft tissue of chin. With all the above-mentioned standard points and measurable planes and angles, cephalometrics aids in skeletal, dental and soft-tissue analysis and classification of various malocclusions. Q. 23. Computerized cephalometric system Q. 24. Nasolabial angle Ans. Nasolabial angle is one of the soft-tissue measurements considered in McNamara analysis. It is formed by drawing a line tangent to the upper lip. Average value is 102 ± 8°. An acute nasolabial angle indicates dentoalveolar protrusion. It may also be due to upturned orientation of the base of the nose. Or Name some data management programmes in computerized cephalometric system. Q. 25. Advantages of computerized cephalometric system Ans. Ans. There are two basic components of computerized cephalometric system: i. Data acquisition ii. Data management. Data acquisition: It is done by either regular radiographs or digital radiographs. Data management: Various commercially available data management programmes are as follows: i. Rocky mountain orthodontics (RMOs) Jiffy orthodontic evaluation ii. Pordios iii. Dentofacial Planner Topic 12 In orthodontics computerized cephalometric systems are employed for the purpose of diagnosis, prognosis and treatment evaluation. The advantages of computerized cephalometric system are as follows: i. Less time consuming ii. Easy to store iii. Easy to retrieve old records iv. Combined evaluation of patient’s photographs, casts and cephalogram is possible v. Efficient in research application. SKELETAL MATURITY INDICATORS LONG ESSAYS Q. 1. Enumerate various methods available to assess skeletal maturity of an individual and its implication in orthodontic diagnosis and treatment planning. Explain in detail about hand–wrist radiographs. Ans. The various skeletal maturity indicators commonly used in orthodontics are as follows: i. Hand–wrist radiographs ii. Evaluation of cervical vertebrae using cephalogram iii. Clinical and radiographic examination of different stages of tooth development, especially canine calcification. Orthodontics-Part-I-2013.indd 119 Clinical implications of skeletal maturity assessment status on diagnosis and treatment planning in orthodontics are as follows: i. The skeletal maturity status of an individual helps in knowing whether the patient will grow appreciably in the treatment period. This has important implications in the treatment planning and response to treatment. ii. While planning orthopaedic therapy, functional appliance therapy and orthognathic surgery, the knowledge of position of the patient in the facial growth curve is important. During the periods of accelerated growth the orthopaedic or functional appliance treatment can 12/3/2013 2:49:19 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 120 contribute significantly to the correction of dentofacial deviations, leading to an improvement in the facial appearance. iii. The skeletal maturity or skeletal age is accurate in assessing the physical maturity. The other parameters like peak height velocity, secondary sexual changes and dental age are inferior to skeletal age in estimating physical maturity. The bones mature at different rate and follow a reasonable sequence; hence, the developmental status of a child can be estimated by the determination of degree of completion of facial skeleton. Hand–wrist radiographs The numerous small bones in the hand–wrist region show a predictable and scheduled pattern of appearance, ossification and union from birth to maturity. Thus, by comparing patient’s hand–wrist radiograph with standard radiographs that represents different skeletal ages, the skeletal maturation status of the individual can be determined. The left hand–wrist is used by convention and a PA view is taken to register the hand–wrist region. Among various methods described to assess skeletal maturity using hand–wrist radiographs, the most commonly used ones are as follows: i. Atlas method by Greulich and Pyle ii. Bjork, Grave and Brown method iii. Fishman’s skeletal maturity indicators iv. Hagg and Taranger method. Anatomy of hand–wrist region Each hand-wrist area has 8 carpals, 5 metacarpals and 14 phalanges, which make a total of 27 bones. Distal ends of radius and ulna also appear in the handwrist radiograph. Radius and ulna are the long bones of the forearm. When the palm faces front, ulna lies in the medial aspect and radius in the distal aspect. Carpal bones were first named by Lyser. These are eight irregularly shaped small bones arranged in two rows: a. Proximal row—scaphoid, lunate, triquetral and pisiform b. Distal row—trapezium, trapezoid, capitate and hamate. These small irregular bones lie in between the long bones of forearm and the metacarpals. Metacarpals are small, long bones and are numbered 1–5, starting from thumb to little finger. Each of the five metacarpals has a base, shaft and head. They lie between the carpals and phalanges forming the skeletal framework of the palm. Phalanges are small bones forming the fingers. Each finger has three phalanges—proximal, middle and distal phalanx. Middle phalanx is absent in the thumb. The phalanges have a pattern of ossification that occurs in three stages: Orthodontics-Part-I-2013.indd 120 i. Stage 1: The epiphysis and diaphysis are equal. ii. Stage 2: The epiphysis caps the diaphysis by surrounding it. iii. Stage 3: The epiphysis and diaphysis are fused. Sesamoid bone is a small nodular bone mostly embedded in tendons in the thumb region. i. Atlas method by Greulich and Pyle Greulich and Pyle published an atlas, which contains pictures of the hand–wrist for different chronological ages for both the sexes. The patient’s radiographs are matched with one of the photographs in the atlas, which is representative of a particular skeletal age. ii. Bjork, Grave and Brown method According to Bjork, the skeletal development in the handwrist area is divided into eight stages—each of them represents a particular level of skeletal maturity. According to Bjork, the stages of skeletal development in hand–wrist region are: Sl. No. Stage Object Growth Phase 1. PP2 Proximal phalanx of index finger Width of epiphysis = width of diaphysis Slow rate of growth 2. MP3 Middle phalanx of middle finger Width of epiphysis = width of diaphysis Maximum long growth imminent 3. S Ulnar sesamoid on metacarpophalangeal joint of thumb Sign of ossification As stage 2 4. MP3 cap Middle phalanx of middle finger Encapsulation of diaphysis Maximum long growth 5. DP3u Distal phalanx of middle finger Epiphysis united Maximum long growth over 6. PP3u Proximal phalanx of middle finger Epiphysis united Maximum long growth over 7. MP3u Middle phalanx of middle finger Epiphysis united Past maximum growth 8. Rc Distal epiphysis of radius and ulna United Growth complete iii. Fishman’s skeletal maturity indicators Leonard S Fishman proposed a system for evaluation of skeletal maturation by making use of anatomical sites located on the thumb, third finger, fifth finger and radius. 12/3/2013 2:49:19 PM
  • Topic wise Solved Questions of Previous Years 121 Covering entire period of adolescent development, 11 discrete skeletal maturity indicators have been described as follows: i. Width of epiphysis and diaphysis are equal in proximal phalanx of third finger. ii. Width of epiphysis equals to that of diaphysis in the middle phalanx of third finger. iii. Width of epiphysis equals to that of diaphysis in the middle phalanx of fifth finger. iv. Appearance of adductor sesamoid of the thumb. v. Capping of epiphysis seen in distal phalanx of third finger. vi. Capping of epiphysis seen in middle phalanx of third finger. vii. Capping of epiphysis seen in middle phalanx of fifth finger. viii. Fusion of epiphysis and diaphysis in the distal phalanx of third finger. ix. Fusion of epiphysis and diaphysis in proximal phalanx of third finger. x. Fusion of epiphysis and diaphysis in the middle phalanx of third finger. xi. Fusion of epiphysis and diaphysis seen in the radius. iv. Hagg and Taranger method Hagg and Taranger noted that skeletal development in hand and wrist can be analysed from the assessment of ossification of ulnar sesamoid of metacarpophalangeal joint of the first finger (S) and certain specified stages of three epiphyseal bones: the middle and distal phalanges of the third finger (MP3 and DP3) and the distal epiphysis of the radius (R) by taking annual radiographs between 6 and 18 years of age. a. Sesamoid It is usually attained during the acceleration period of the pubertal growth spurt, i.e. onset of peak height velocity. b. Stages of ossification of middle phalanx of third finger (MP3) They follow pubertal growth spurt. The stages of ossification are outlined from stage F to stage I as follows: i. Stage F: The epiphysis is as wide as the metaphysis. About 40% of the individuals are before peak height velocity (PHV). Very few are at PHV. ii. Stage FG: The epiphysis is as wide as the metaphysis, and there is a distinct medial or lateral (or both) border of the epiphysis forming a line of demarcation at right angles to the border. About 90% of the individuals are 1 year before or at PHV. iii. Stage G: The sides of the epiphysis are thickened and there is capping of the metaphysis, forming a sharp edge distally at one or both sides. About 90% of the individuals are at or 1 year after PHV. iv. Stage H: Fusion of the epiphysis and metaphysis has begun. About 90% of the girls and all the boys are after PHV, but before the end of the pubertal growth spurt. v. Stage I: Fusion of the epiphysis and metaphysis is completed. All individuals except a few girls have ended the pubertal growth spurt. c. Distal phalanx of third finger DP3-I: Fusion of the epiphysis and metaphysis is completed. This stage signifies the fusion of the epiphysis and metaphysis, and is attained during the deceleration period of the pubertal growth spurt (i.e. end of PHV) by all subjects. d. Radius R–I: Beginning of fusion of the epiphysis and metaphysis. In about 80% of the girls and 90% of the boys, this stage is attained 1 year before or at the end of growth spurt. R–IJ: Fusion is almost completed but there is still a small gap at one or both margins. R–J: Fusion of the epiphysis and metaphysis occurred. None of the subjects had attained these stages before the end of PHV. SHORT ESSAYS Q.1. Hand–wrist radiography Or How hand–wrist radiographs are useful in orthodontic diagnosis and treatment planning? Ans. i. Among the various skeletal maturity indicators, hand– wrist radiographs are commonly used in orthodontics. Orthodontics-Part-I-2013.indd 121 ii. The numerous small bones in the hand–wrist region show a predictable and scheduled pattern of appearance, ossification and union from birth to maturity. Thus, by comparing patient’s hand–wrist radiograph with standard radiographs that represents different skeletal ages, the skeletal maturation status of the individual can be determined. iii. The left hand–wrist is used by convention and a PA view is taken to register the hand–wrist region. 12/3/2013 2:49:20 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 122 iv. Among various methods described to assess skeletal maturity using hand–wrist radiographs, the most commonly used ones are as follows: a. Atlas method by Greulich and Pyle b. Bjork, Grave and Brown method c. Fishman’s skeletal maturity indicators d. Hagg and Taranger method. v. Atlas method by Greulich and Pyle Greulich and Pyle published an atlas that contains pictures of the hand–wrist for different chronological ages for both the sexes. The patient’s radiographs are matched with one of the photographs in the atlas, which is representative of a particular skeletal age. vi. Bjork, Grave and Brown method: According to Bjork, the skeletal development in the hand–wrist area is divided into eight stages—each of them represents a particular level of skeletal maturity. vii. Fishman’s skeletal maturity indicators: Leonard S Fishman proposed a system for evaluation of skeletal maturation by making use of anatomic sites located on the thumb, third finger, fifth finger and radius. Covering entire period of adolescent development, 11 discrete skeletal maturity indicators have been described. viii. Hagg and Taranger method Hagg and Taranger noted that skeletal development in hand and wrist can be analysed from the assessment of ossification of ulnar sesamoid of metacarpophalangeal joint of the first finger (S) and certain specified stages of three epiphyseal bones—the middle and distal phalanges of the third finger (MP3 and DP3) and the distal epiphysis of the radius (R) by taking annual radiographs between 6 and 18 years of age. Q. 2. Compare skeletal age and dental age. Or Dental versus skeletal age Ans. Skeletal age Dental age It is based on the ossification The formation of teeth or eruption of of endochondral bone. the teeth is the basis for calculating dental age. It is assessed based on the skeletal maturity indicators like hand–wrist radiographs, cervical vertebrae, etc. Orthodontics-Part-I-2013.indd 122 It is assessed based on the number of teeth at each chronological age or on stages of formation of crowns and roots of the teeth. Skeletal age Dental age It helps in assessing physical It has no role in physical maturity asmaturity of an individual. sessment. It is helpful in treatment plan- It can reflect an assessment of physining and tracking response to ologic age comparable to age based treatment. on the skeletal development, weight or height. There is correlation between When the last tooth has completed its the dental age and skeletal development, it is an indication that age. the skeleton is approaching complete maturation. Q. 3. Cervical vertebrae as skeletal maturity indicators Ans. A system of skeletal maturation determination using cervical vertebrae was introduced by Hassel and Farman. The shapes of the cervical vertebrae were seen to differ at each level of skeletal development, which provided a mean to determine the skeletal maturity of a person and thereby helps to estimate whether the possibility of potential growth existed. The six stages put forward by Hassel and Farman in assessing skeletal growth are named as follows: i. Stage 1: Initiation ii. Stage 2: Acceleration iii. Stage 3: Transition iv. Stage 4: Deceleration v. Stage 5: Maturation vi. Stage 6: Completion. Changes observed at various stages are as follows: i. Stage 1: Initiation Marks the beginning of adolescent growth with 80–95% of adolescent growth expected. Inferior borders of C2, C3 and C4 were flat and superior borders were tapered from posterior to anterior and vertebrae were wedge shaped. ii. Stage 2: Acceleration Acceleration of growth begins at this stage with 65–85% of adolescent growth expected. Concavities are seen in lower borders of C2 and C3, and lower border of C4 will be flat. The bodies of C3 and C4 were nearly rectangular in shape. iii. Stage 3: Transition Corresponds to acceleration of growth to peak height velocity with 25–65% of adolescent growth expected. 12/3/2013 2:49:20 PM
  • Topic wise Solved Questions of Previous Years 123 Marked concavities are seen in lower borders of C2 and C3, and a concavity was beginning to develop in the lower border of C4. The bodies of C3 and C4 were rectangular in shape. iv. Stage 4: Deceleration Deceleration of adolescent growth spurt with 10–25% of adolescent growth expected. Marked concavities are seen in C2, C3 and C4 in their lower borders. Shape of vertebral bodies of C3 and C4 is square shaped. v. Stage 5: Maturation Final maturation of vertebrae took place during this stage with 5–10% of adolescent growth expected. More accentuated concavities are seen in lower borders of C2, C3 and C4. The bodies of C3 and C4 are square in shape. vi. Stage 6: Completion This stage corresponds to completion of growth. Little or no adolescent growth is expected. More accentuated concavities are seen in lower borders of C2, C3 and C4. The body shapes of C3 and C4 were square or were greater in vertical dimension than in horizontal dimension. Q. 4. Implant radiography in orthodontics Ans. i. Implant radiography is an experimental method for studying physical growth. ii. Professor Bjork introduced human implant radiograph for growth measurement. iii. Procedure Inert metal pins, e.g. tantalum pins of size 1.5 mm long and 0.5 mm diameter were placed in the mandible. These metal pins get osseointegrated and serve as reference points. Serial cephalometric radiographs are taken repeatedly over a period of time and compared. Only implant radiography can estimate rotation of jaw bones. iv. Information obtained from implant radiography: It gives very accurate information about site of growth, amount of growth and direction of growth, and relatively accurate information about rate of growth. v. Drawbacks It is a two-dimensional study of a three-dimensional process. Radiation hazard. SHORT NOTES Q. 1. Carpals Or Carpal index Ans. i. Carpals are the bones of hand–wrist region. ii. These were first named by Lyser. iii. These are eight irregularly shaped small bones arranged in two rows: a. Proximal row—scaphoid, lunate, triquetral and pisiform b. Distal row—trapezium, trapezoid, capitate and hamate. These small irregular bones that lie in between the long bones of forearm and the metacarpals. iv. Each carpal bone ossifies from one primary centre, which appears in a predictable pattern. Q. 2. Hand–wrist radiographs Or Orthodontics-Part-I-2013.indd 123 Hand–wrist radiography Ans. i. Hand–wrist radiographs are one among the various skeletal maturity indicators commonly used in orthodontics. ii. The numerous small bones in the hand–wrist region show a predictable and scheduled pattern of appearance, ossification and union from birth to maturity. Thus, by comparing patients’ hand–wrist radiograph with standard radiographs that represents different skeletal ages, the skeletal maturation status of the individual can be determined. iii. Among various methods described to assess skeletal maturity using hand–wrist radiographs, the most commonly used ones are as follows: a. Atlas method by Greulich and Pyle b. Bjork, Grave and Brown method c. Fishman’s skeletal maturity indicators d. Hagg and Taranger method. 12/3/2013 2:49:20 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 124 Q. 3. Skeletal age Ans. i. The skeletal maturity or skeletal age is more superior and accurate in assessing the physical maturity than the other parameters like peak height, velocity, secondary sexual changes and dental age. ii. Skeletal age is based on the ossification of endochondral bone. iii. It can be assessed based on various skeletal maturity indicators like hand–wrist radiographs, evaluation of cervical vertebrae, and clinical and radiographic examination of different stages of tooth development. iv. Assessing the skeletal maturity is helpful in diagnosis, treatment planning and response to treatment in orthodontics. v. The dental and skeletal ages correlate with each other. Q. 4. Vital staining Ans. i. Vital staining is one of the experimental methods of measuring growth introduced in 18th century by John Hunter. ii. It consists of injecting dyes that stain and get deposited in the mineralizing tissues like bones and teeth. Example: Commonly used dyes for vital staining are alizarin Topic S, radioactive tracers, fluorochrome, tetracycline and trypan blue. iii. Animals are sacrificed and tissues are studied histologically. iv. This cross-sectional study elicits information regarding detailed analysis of site and amount of growth as well as the rate of growth. v. Disadvantage: It is not a longitudinal study, i.e. repeated data of the same individual cannot be obtained. Q. 5. Dental age Ans. i. Dental age usually correlates with chronological age and is assessed based on: a. Amount of root resorption of primary teeth b. Teeth that have erupted c. Amount of permanent teeth development. ii. Dental age is assessed on the basis of the number of teeth at each chronological age or at stages of formation of crowns and roots of the teeth. iii. Dental age can reflect an assessment of physiologic age comparable to age based on the skeletal development, weight or height. iv. Complete formation of last tooth is an indication that the skeleton is approaching complete maturation. 13 MODEL ANALYSIS LONG ESSAYS Q. 1. Enumerate the various diagnostic aids used in orthodontics and add a note on study models. Ans. The various diagnostic aids used in orthodontics are as follows: Orthodontic diagnostic aids Essential diagnostic aids Non-essential or supplemental diagnostic aids (these are very important for all (these are not essential in the cases, are simple and do not all cases and require special require expensive equipment) equipment) Orthodontics-Part-I-2013.indd 124 For example: For example: a. Case history and clinical ex- a. Specialized radiographs b. Electromyography amination c. Hand–wrist radiographs b. Study models d. Endocrine tests c. Certain basic radiographs e. Estimation of BMR d. Facial photographs f. Diagnostic setup g. Occlusograms Study models are one of the essential orthodontic diagnostic aids that make it possible to study the arrangement of teeth and occlusion from all three planes, namely, sagittal, vertical and transverse planes of space. Uses of study models i. These allow study of occlusion from all aspects. ii. These enable accurate measurements to be made in dental arch such as arch length, arch width and tooth size. 12/3/2013 2:49:20 PM
  • Topic wise Solved Questions of Previous Years 125 iii. Assessment of treatment progresses by both the patient as well as the dentist. iv. These help in assessing the nature and severity of malocclusion as well as motivation of the patient to orthodontic therapy. v. These are useful to explain treatment plan as well as progress of treatment to the patient and parents. vi. These make it possible to simulate treatment procedures on cast called ‘mock surgery’. vii. In case the patient is to be treated by another dentist, these make it easy to transfer records of the patient. Ideal requirements of a study model The study models should accurately reproduce the teeth and surrounding soft tissues, without any distortion. They should not only depict the teeth but also reproduce as much of alveolar process as possible, with a clean, smooth and nodule-free surface. They should be trimmed in such a way that they are symmetrical and pleasing to the eye. When placed on their backs, they should accurately reproduce the occlusion and enable instant identification of asymmetries in the arch form. Parts of a study model The orthodontic study model consists of the following parts (Fig. 13.1): i. Anatomic portion ii. Artistic portion. Anatomic portion Artistic portion Fig. 13.1 Orthodontic study model. The anatomic portion of study model is the actual impression of the dental arch and its surrounding structures. Usually this portion is made of stone plaster. The artistic portion of study model consists of a plaster base that supports the anatomic portion. In a well-fabricated set of study models the ratio of anatomic portion to artistic portion should be 3:1. Construction of study models The steps involved in construction of study models are as follows: i. Impression making ii. Disinfection of the impression iii. Casting the impression iv. Basing and trimming of the cast v. Finishing and polishing. i. Impression making: It is an important step in making orthodontic study models, as they should accurately reproduce as much of supporting structures as possible. The ideal trays should be selected such that they include last erupted molars and should have a clearance of around 3 mm between the teeth and the tray. The irreversible hydrocolloids or alginates are widely used materials for making impressions. ii. Disinfecting the impression: This can be done by soaking the impression in a disinfectant solution such as biocide, 2% glutaraldehyde for a specified duration of time. iii. Casting the impression: Impressions obtained are usually casted on orthodontic stone or model stone. iv. Basing and trimming of the cast: Rubber base formers are available to help in making the base (i.e. the artistic portion of the study cast) over the anatomic portion. The trimming of the orthodontic model is a meticulous process done on electric plaster trimming machine. v. Finishing and polishing: The final polishing of the cast is done by placing them in a soap solution for 1 hour and is then removed and rinsed under coal water. The casts are then allowed to dry and are buffed to acquire smooth and shining appearance. They can be polished using fine-grained sandpaper. The finished study models can be stored in boxes for future reference. SHORT ESSAYS Q. 1. Pont’s analysis Or Pont’s index Ans. Orthodontics-Part-I-2013.indd 125 Pont’s analysis was presented by Pont in 1909. Pont’s index or Pont’s analysis is a method of predetermining the ideal arch width based on mesiodistal width of crowns of maxillary incisors. By this analysis the width of the arch in the premolar and molar regions can be established by the measurement of the greatest width of maxillary incisors. 12/3/2013 2:49:20 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 126 The parameters considered in this analysis are: i. Determination of sum of incisors (SI): The summed up value of mesiodistal width of the four maxillary incisors is known as the sum of incisors (SI) (Fig. 13.2). 2 1 1 2 iv. Determination of calculated premolar value (CPV): The expected arch width in the premolar region or calculated premolar value is determined by the formula: SI × 100/80. v. Determination of calculated molar value (CMV) The expected arch width in the molar region or calculated molar value is determined by the formula: SI × 100/64. Inference: If measured value is less than calculated value, it indicates the need for expansion. Whether dental arch is narrow or normal Uses of Pont’s analysis: It helps to determine Need for lateral expansion of arch How much expansion is possible at the premolar and molar regions? Q. 2. Korkhaus analysis Ans. Fig. 13.2 Sum of incisors (SI). ii. Determination of measured premolar value (MPV): The MPV is the arch width in the premolar region from distal pit of one upper first premolar to the distal pit of opposite first premolar (Fig. 13.3). Korkhau, in 1938, proposed a study model analysis that reveals anteroposterior malpositioning of incisors in maxillary and mandibular arches (Fig. 13.5). 1st premolar 1st premolar Fig. 13.5 Korkhaus analysis. Fig. 13.3 MPV. iii. Determination of measured molar value (MMV): The MMV is the arch width in the molar region from the mesial pit of one upper first molar to the mesial pit of the opposite first molar (Fig. 13.4). Method i. Sum of upper incisors (SIu) = Added measurement of mesiodistal width of maxillary incisors. ii. Available anterior arch length (AAAL) = A measurement made from the midpoint of the interpremolar line to a point between the two maxillary incisors. iii. The ideal anterior arch length (IAAL) is determined by using Korkhaus formula: SIu × 100 160 iv. If AAAL > IAAL, it indicates that maxillary central incisors are malpositioned anteriorly. For example: labioversion of anteriors, bimaxillary protrusion. v. If AAAL < IAAL, it indicates that maxillary central incisors are malpositioned posteriorly. For example: linguoversion of anteriors, class II division 2 malocclusion. IAAL = 1st premolar 1st premolar Fig. 13.4 MMV. Orthodontics-Part-I-2013.indd 126 12/3/2013 2:49:20 PM
  • Topic wise Solved Questions of Previous Years 127 vi. AAL is measured in the mandibular arch in similar manner, whereas the arch width at the premolar region is taken from contact areas of first premolar and second premolar. vii. According to Korkhaus, for a given width of upper incisors a specific value of the distance between the midpoint of interpremolar line to the point between the two maxillary incisors should exist. An increase in this measurement denotes proclined upper anterior teeth while a decrease in this value denotes retroclined upper anterior teeth. Q. 3. Carey’s analysis Or Carey’s analysis or arch perimeter analysis Ans. The main cause of most of the malocclusions is the arch length and tooth material discrepancy. This discrepancy can be calculated with the help of Carey’s analysis. Carey’s analysis is usually done in the lower arch (cast). If the same analysis is performed on the upper arch (cast), it is known as arch perimeter analysis. Method i. Determination of arch length ii. Determination of tooth material iii. Determination of discrepancy. i. Determination of arch length: It is carried with a soft brass wire. Arch length is measured from mesial surface of first permanent molar of one side to the first permanent molar of the opposite side. If the anterior teeth are well-aligned, the brass wire passes over the incisal edges of anteriors; if they are retroclined, the brass wire in the anterior segment passes labial to the teeth; in case of proclined anteriors, the wire is passed along the cingulum of anterior teeth. ii. Determination of tooth material: The tooth material is measured by summing up the mesiodistal width of individual teeth anterior to the first molars, i.e. second premolar to second premolar. iii. Determination of discrepancy: Discrepancy refers to the difference between the arch length and tooth material. Assessment of tooth mass discrepancy Ans. Ashley Howe’s analysis is a model analysis to study the relationship of tooth size to the size of supporting structures. Ashley Howe considered that tooth crowding is due to deficiency in arch width rather than arch length. He found that a relationship exists between the total width of 12 teeth anterior to the second molars and the width of dental arch in the first premolar region. The following parameters are considered: i. Determination of total tooth material (TTM) ii. Determination of premolar diameter (PMD) iii. Determination of premolar basal arch width (PMBA). i. Total tooth material (TTM): The mesiodistal width of all the teeth mesial to second permanent molars is measured and summed up. This value is called total tooth material (TTM) (Fig. 13.6). 1 2 1 2 3 3 4 5 C 1st PM 2nd PM 6 L1 1st M C1 C2 L2 C 1st PM 4 5 2nd PM 6 1st M Fig. 13.6 Total tooth material. ii. Determination of premolar diameter (PMD): The premolar diameter is the arch width measured from tip of the buccal cusp of one first premolar to the opposite first premolar (Fig. 13.7). Inference If the discrepancy is 0–2.5 mm—it indicates minimum tooth material excess and suggests proximal stripping to reduce tooth material. 2.5–5 mm—it indicates need to extract the second premolar. >5 mm—it indicates need to extract first premolars. Q. 4. Ashley Howe’s index Or Orthodontics-Part-I-2013.indd 127 Fig. 13.7 Premolar diameter. 12/3/2013 2:49:20 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 128 iii. Determination of premolar basal arch width (PMBA): The measurement of width from canine fossa of one side to other gives the width of dental arch at the apical base. If canine fossa is not clear, measurement is made from a point about 8 mm below the crest of the interdental papilla distal to canine. Inference Comparison between PMBAW and the PMD: If the PMBAW > PMD—it is an indication that arch expansion is possible. If PMAW < PMD—arch expansion is not possible. According to Ashley Howe, the ratio between the apical base width at the premolar region and the total tooth material is called the premolar basal arch width percentage. To determine discrepancy, the predicted tooth size of 3, 4 and 5 are compared with available arch length. If predicted value is greater than arch length, crowding is expected. Q. 6. Radiographic method of mixed dentition analysis Ans. The radiographic method of mixed dental analysis makes use of both radiograph as well as study cast to determine the width of unerupted tooth to compensate for enlargement of radiographic image. A simple proportionality relationship can be setup to determine the measurement of the unerupted teeth by studying the teeth that have already erupted in a radiograph and on cast by the following formula: PMBAW% = PMBAW × 100 TTM Inference is that if: PMBAW% is 37% or less—it indicates need for extraction. PMBAW% is 44% or more—the case can be treated without extracting any teeth. PMBAW% is 37 to 44%—the case is a borderline case. Q. 5. Mixed dentition analysis. Explain one in detail. Or Moyer’s mixed dentition analysis Ans. Moyer’s mixed dentition analysis The purpose of Moyer’s analysis is to evaluate the amount of space available in the arch for succeeding permanent canines and premolars. Moyer’s mixed dentition analysis predicts the combined mesiodistal width of 3, 4 and 5 based on the sum of the widths of the four lower permanent incisors, i. e. 21 21 . The mesiodistal width of 21 21 is measured and summed up. The amount of space available for 3, 4 and 5 after incisor alignment is determined by measuring the distance 2 and mesial surface of 6. Based on mesiodistal width of 21 21 , the expected width of 3, 4 and 5 are predicted by referring to probability chart. Seventy-five percent of level of probability is considered reliable. Orthodontics-Part-I-2013.indd 128 Apparent width of unerupted = tooth Width of tooth that has erupted and measured on the radiograph Undistorted radiographic image is usually achieved with individual periapical radiographs. Accuracy of this method is fair to good, depending on the quality of radiographs. This technique can be used in maxillary and mandibular arches for all ethnic groups. Q. 7. Bolton’s tooth size ratio Various mixed dentition analyses to study the relationships of tooth size and available space during mixed dentition period are as follows: Moyer’s mixed dentition analysis Tanaka–Johnston analysis Staley and Kerber analysis Radiographic method. between distal surface of True width of tooth that has erupted and measured on cast × Width of unerupted tooth on radiograph Or Bolton’s analysis Ans. Bolton’s analysis evaluates the maxillary and mandibular teeth for tooth size discrepancies. According to Bolton, a ratio exists between the mesiodistal widths of maxillary and mandibular teeth. Abnormalities in tooth size are responsible for occurrence of many malocclusions. Bolton’s analysis helps in determining disproportion in size between maxillary and mandibular teeth. The parameters considered are as follows: i. Sum of mandibular 12 teeth—measured and summed up value of mesiodistal widths of all teeth mesial to 7 7. ii. Sum of maxillary 12 teeth—measured and summed up value of mesiodistal width of all teeth mesial to 7 7. iii. Sum of mandibular 6 teeth—measured and summed up value of mesiodistal width of all teeth mesial to 4 4. iv. Sum of maxillary 6 teeth—measured and summed up value of mesiodistal width of all teeth mesial to 4 4. 12/3/2013 2:49:20 PM
  • Topic wise Solved Questions of Previous Years 129 Q. 8. Kesling tooth positioning Determination of overall ratio Sum of maxillary 12 Kesling’s diagnostic setup According to Bolton, sum of mesiodistal width of mandibular teeth anterior to 7 7 should be 91.3% of the mesiodistal width of maxillary teeth mesial to 7 7. If overall ratio is <91.3% Maxillary tooth material excess >91.3% Mandibular teeth material excess Calculate by formula: Calculate by formula: Maxillary 12 = Mandibular 12 × 100 91.3 Mandibular 12 = Maxillary 12 × 91.3 100 Determination of anterior ratio Anterior ratio = Sum of mandibular 6 × 1000 Sum of maxillary 6 According to Bolton, sum of mesiodistal width of mandibular anteriors should be 77.2% of mesiodistal width of maxillary anteriors. If anteriors’ ratio is <77.2% Indicates maxillary anterior excess >77.2% Indicates mandibular anterior excess Calculate by formula: Calculate by formula: Sum of maxillary 6 = Or Sum of mandibular 12 × 100 Overall ratio = Sum of Mandibular 6 × 100 77.2 Sum of mandibular 6 = Sum of Maxillary 6 × 77.2 Ans. HD Kesling (1956) proposed a diagnostic setup that helps the clinician to estimate arch length discrepancy. Procedure The patient’s maxillary and mandibular study casts revealing supporting structures to the depth of the sulcus are prepared with their bases parallel to occlusal plane . Using a Fretsaw blade horizontal cuts are made in the mandibular cast 3 mm below the gingival margin and vertical cuts are made between individual teeth so that we can remove all the teeth except second and third molars. Mesial and distal ends of the roots of teeth are trimmed to facilitate seating in the new position. The mandibular incisors are arranged at 65o angle to the Frankfurt horizontal plane while canines and premolars are placed in correct contact relationship. If the remaining space is inadequate to receive the first molars, the extractions are indicated. Therefore, the first premolars are eliminated from the setup and second premolars are placed in contact with the canine. Maxillary teeth are cut and repositioned, articulating with mandibular setup. Uses The tooth size–arch length discrepancies can be directly visualized on the diagnostic setup. It serves as a guide in including extractions and visualizing complex orthodontic tooth movements on the study casts. It also helps in estimating whether only uprighting of second molars could solve the problem of arch length discrepancy. Patients can be motivated by simulating tooth movements on the study casts. 100 SHORT NOTES Q. 1. Pont’s analysis Or Pont’s index Ans. Orthodontics-Part-I-2013.indd 129 Pont’s index or Pont’s analysis is a method of predetermining the ideal arch width based on mesiodistal width of crowns of maxillary incisors. By this analysis the width of the arch in the premolar and molar regions can be established by the measurement of the greatest width of maxillary incisors. 12/3/2013 2:49:20 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 130 The parameters considered in this analysis are: i. Determination of sum of incisors (SI) ii. Determination of measured premolar value (MPV) iii. Determination of measured molar value (MMV) iv. Determination of calculated premolar value (CPV) v. Determination of calculated molar value (CMV). The calculated premolar value is determined by the formula: CPV = SI × 100/80 The calculated molar value is determined by the formula: CMV = SI × 100/64 Inference is that if measured value is less than the calculated value it indicates the need for expansion. Q. 2. Model analysis Ans. The evaluation of maxillary and mandibular teeth and their supporting structures using study casts is known as model analysis. Model analysis can be classified as follows: i. Analysis to study the size relationships of groups of teeth For example: Bolton’s analysis, peck and peck ratio. ii. Analysis to study the relationship of teeth size to the size of supporting structures For example: Ashley Howe’s analysis, Pont’s analysis. iii. Analysis to study mixed dentition For example: Moyer’s analysis, Tanaka–Johnston analysis. iv. Analysis to study the relationship of tooth size and available space in permanent dentition For example: Carey’s analysis, arch perimeter analysis. Q. 3. Carey’s analysis Or Arch perimeter analysis Ans. The arch length and tooth material discrepancy can be calculated with the help of Carey’s analysis. Carey’s analysis is usually done in the lower arch (cast). If the same analysis is performed on the upper arch (cast), it is known as arch perimeter analysis. It involves determination of arch length, tooth material and discrepancy. Arch length is measured from mesial surface of first permanent molar of one side to the first permanent molar of the opposite side. The tooth material is measured by summing up the mesiodistal width of individual teeth anterior to the first molars, i.e. second premolar to second premolar. Orthodontics-Part-I-2013.indd 130 The discrepancy refers to the difference between the arch length and tooth material. Inference If the discrepancy is: 0–2.5 mm—indicates minimum tooth material excess and suggests proximal stripping to reduce tooth material. 2.5–5 mm—indicates need to extract the second premolar. 5 mm—indicates need to extract first premolars. Q. 4. Peck and peck ratio Ans. Chief rationale for peck concept is stability of rotational corrections of lower incisors rather than tooth size considerations. It is calculated as: Mesiodistal width × 100 Faciolingual diameter Normal ratio for central incisors is 88–92% and for lateral incisors it is 90–95%. Peck and peck ratio is used to determine whether lower incisor teeth are excessively wider mesiodistally; if so, proximal slicing is recommended. Peck and peck ratio = Q. 5. Name few model analysis for mixed dentition. Ans. Various analyses to study the relationship of tooth size and available space during mixed dentition are as follows: i. Moyer’s mixed dentition analysis ii. Tanaka–Johnston analysis iii. Staley and Kerber analysis iv. Radiographic method. Q. 6. Linderhearth’s ratio Ans. Linderhearth’s ratio is a method of predetermining the ideal arch width based on mesiodistal width of crowns of maxillary incisors, similar to Pont’s index. The ratio of combined incisor to transverse arch width, as measured from the centre of occlusal surface of teeth, is ideally 0.85 in first premolar area and 0.65 in the first molar area according to Linderhearth. The sum of the mesiodistal widths of maxillary incisors are measured and added (SI). The calculated premolar value is determined by the formula: CPV = SI × 100 85 12/3/2013 2:49:20 PM
  • Topic wise Solved Questions of Previous Years 131 The calculated molar value is determined by the formula: SI × 100 64 Inference is that if the measured value is less than calculated value it indicates the need for expansion. CMV = Q. 7. Radiographic method of mixed dentition analysis Ans. Bolton’s analysis evaluates the maxillary and mandibular teeth for tooth size discrepancies. Abnormalities in tooth size are responsible for occurrence of many malocclusions. According to Bolton, a ratio exists between the mesiodistal widths of maxillary and mandibular teeth. Determination of overall ratio: Overall ratio = The radiographic method of mixed dental analysis makes use of both radiograph as well as study cast. A simple proportionality relationship can be setup to determine the measurement of the unerupted teeth by studying the teeth that have already erupted in a radiograph and on cast by the following formula: True width of tooth that has erupted and measured on cast × width of unerupted tooth on Apparent width of radiograph unerupted tooth = Width of tooth that has erupted and measured on the radiograph Accuracy of this method is fair to good, depending on quality of radiographs. This technique can be used in maxillary and mandibular arches for all ethnic groups. Q. 8. Study models—uses Ans. Study models are one of the essential orthodontic diagnostic aids. Uses of study models are as follows: These allow study of occlusion from all aspects. These help in assessing the nature and severity of malocclusion as well as motivation of the patient to orthodontic therapy. These are useful to explain treatment plan as well as progress of treatment to the patient and parents. In case the patient is to be treated by another dentist, these make it easy to transfer records of the patient. Q. 9. Bolton’s analysis Or Bolton’s tooth size ratio Or Bolton index. Ans. Orthodontics-Part-I-2013.indd 131 Sum of mandibular 12 teeth × 100 Sum of maxillary 12 teeth According to Bolton, sum of mesiodistal width of mandibular teeth anterior to 7 7 should be 91.3% of the mesiodistal width of maxillary teeth mesial to 7 7 . If the overall ratio is <91.3%, it indicates maxillary tooth material excess If it is >91.3%, it indicates mandibular teeth material excess. Determination of anterior ratio: Anterior ratio = Sum of mandibular 6 × 1000 Sum of maxillary 6 According to Bolton, the sum of mesiodistal width of mandibular anteriors should be 77.2% of mesiodistal width of maxillary anteriors. If anteriors ratio is <77.2%, it indicates maxillary anterior excess; if it is >77.2%, it indicates mandibular anterior excess. Q. 10. Tanaka–Johnston analysis Ans. Tanaka–Johnston analysis is a mixed dentition analysis. It predicts the widths of unerupted canines and premolars based on sum of the widths of lower incisors. Method Measure the total arch length. Measure the mesiodistal widths of lower four incisors and sum them up. Divide the value obtained by 2 and ❍ Add 10.5 mm to obtain the sum of widths of mandibular canines and premolars in one quadrant. ❍ Add 11 mm to obtain the sum of widths of maxillary canines and premolars in one quadrant. Formula to calculate the space available in the arch after the eruption of canines and premolars is as follows: Space available = Total arch length – Sum of the lower incisors + 2 × Calculated width of canine and premolar Advantages: It is simple and practical, requires neither radiographs nor reference tables, and shows reasonably good accuracy. 12/3/2013 2:49:20 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 132 Q. 11. Korkhaus analysis Ans. Korkhaus in 1938 proposed a study model analysis, which reveals anteroposterior malpositioning of incisors in maxillary and mandibular arches. A measurement is made from the midpoint of the interpremolar line to a point between the two maxillary incisors. According to Korkhaus, for a given width of upper incisors a specific value of the distance between the midpoint of interpremolar line to the point between the two maxillary incisors should exist. An increase in this measurement denotes proclined upper anterior teeth, while a decrease in this value denotes retroclined upper anterior teeth. Q.12. Gnathostatic models Ans. Gnathostatic models or gnathostatic casts reproduce inclination of the occlusal plane with reference to the Frankfurt plane. Paul Simon developed an instrument called gnathometer (1928–1934). Gnathostatics is a diagnostic medium related to teeth and their base to each other and to the craniofacial structures. Simon tried to orient and relate the dentition and the jaws with the help of dental study models to cranium. His effort was to give the orthodontist a real insight into the orientation of the dentition to the facial skeleton in three planes of space, thereby helping to modulate treatment plan in the direction of restoration of facial balance. individual teeth so that we are able to remove all teeth except second and third molars. The mandibular incisors are arranged at 65o angle to the Frankfurt horizontal plane, while canines and premolars are placed in correct contact relationship. If the remaining space is inadequate to receive the first molars, the extractions are indicated. Maxillary teeth are cut and repositioned articulating with mandibular setup. It serves as a guide in including extractions and visualizing complex orthodontic tooth movements on the study casts. Q. 14. Ashley Howe’s index Ans. Ashley Howe’s analysis is a model analysis to study the relationship of tooth size to the size of supporting structures. He found that a relationship exists between the total width of 12 teeth anterior to the second molars and the width of dental arch in the first premolar region. He considered following parameters: Total tooth material (TTM), premolar diameter (PMD) and premolar basal arch width (PMBA). Inference The PMBAW and the PMD are compared as follows: ❍ If the PMBAW > PMD—it is an indication that arch expansion is possible. ❍ If PMAW < PMD—arch expansion is not possible. According to Ashley Howe’s the ratio between the apical base width at the premolar region and the total tooth material is called the premolar basal arch width percentage. Q. 13. Kesling’s diagnostic setup Ans. HD Kesling (1956) proposed a diagnostic setup, which helps the clinician to estimate arch length discrepancy. Procedure Patients maxillary and mandibular study casts are prepared as per guidelines. Using a Fretsaw blade, required cuts are made between Orthodontics-Part-I-2013.indd 132 PMBAW% = PMBAW × 100 TTM Inference is that if: If PMBAW% is: 37% or less—it indicates the need for extraction. 44% or more—the case can be treated without extracting any teeth. 37–44%—the case is a borderline case. 12/3/2013 2:49:20 PM
  • Topic wise Solved Questions of Previous Years 133 Topic 14 BIOLOGY AND MECHANICS OF TOOTH MOVEMENT LONG ESSAYS Q. 1. Define optimal orthodontic force. Discuss tissue changes subsequent to light and heavy forces. Or Describe the tissue changes subsequent to orthodontic force application. Or Discuss the histological changes during orthodontic tooth movement. Or Describe the various histological tissue changes during active orthodontic treatment. Ans. Optimum orthodontic force is one that moves teeth most rapidly in desired direction with least possible damage to tissue and minimum patient discomfort. Optimum orthodontic force = capillary pulse pressure, i.e. 20–26 g/cm2 of root surface area. Characteristics of optimum orthodontic force a. From clinical point of view: i. Produces rapid tooth movement ii. Minimum patient discomfort iii. Minimum lag phase of tooth movement iv. No marked mobility of teeth being moved b. From histological point of view: i. Vitality of tooth and supporting PL is maintained ii. Initiates maximum cellular response iii. Produces direct frontal resorption. Tissue changes subsequent to orthodontic force application When force is applied on a tooth to bring about orthodontic movement, it results in formation of: i. Areas of pressure (in the direction of tooth movement): Bone subjected to pressure reacts by bone resorption. ii. Areas of tension (in the opposite direction): Bone subjected to tension exhibits bone deposition. iii. When tooth is moved due to application of orthodontic force there is bone resorption on pressure side and new bone formation on tension side. Orthodontics-Part-I-2013.indd 133 iv. Histological changes during tooth movements are studied under two headings: a. Changes following application of mild force b. Changes following application of extreme force. a. Changes following application of mild force Changes on pressure side (tooth movement side) Periodontal ligament compressed to one-third of its original thickness. Marked ↑ in vascularity of periodontal ligament due to capillary blood supply—mobilization of cells, fibroblasts and osteoclasts. Osteoclasts lie in shallow depressions of bone called Howship’s lacunae: They start resorbing bone. When the forces applied are within physiologic limits, the resorption seen in the alveolar plate immediately becomes adjacent to the ligament. This kind of resorption is called frontal resorption. A change in the orientation of bony trabeculae is seen several weeks after continued orthodontic force application. The trabeculae are usually parallel to long axis of teeth they become horizontally oriented, i.e. parallel to direction of orthodontic force. The trabecular pattern reverts back to normal during retention phase of treatment. Changes on tension side (area of tooth opposite to direction of force) Periodontal ligament gets stretched: Distance between alveolar bone and tooth is widened. ↑Vascularity is seen (just as on pressure side): Mobilization of cells, fibroblasts, osteoblasts. In response to this traction, osteoid is laid down by osteoblasts in periodontal ligament immediately adjacent to the lamina dura. This lightly calcified bone in due course of time matures to form woven bone. Secondary remodelling changes When the force is applied to move teeth, the bone immediately adjacent shows osteoclastic and osteoblastic activity on the pressure and tension side, respectively. In addition, bony changes also take place elsewhere to maintain the width or thickness of the alveolar bone. These changes are called secondary remodelling changes. Example: If a tooth is being moved in labial direction, 12/3/2013 2:49:21 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 134 there is compensatory deposition of new bone on the outer side of labial alveolar bony plate and also a compensatory resorption on the lingual side of lingual alveolar bone. Tooth moved in labial direction ϩ Ϫ Ϫ ϩ Ϫ ϩ Ϫ ϩ ϩ Ϫ Ϫ ϩ Ϫ ϩ Ϫ Ϫ ϩ Ϫ ϩ Ϫ Ϫ ϩ Ϫ Ϫ Fig. 14. 1 Secondary remodelling changes seen following application of bodily force in labial direction (Not: +++: bone deposition, ---bone resorption). Secondary remodelling changes seen following application of bodily force in labial direction. These compensatory structural alterations maintain the thickness of supporting alveolar process even though tooth may be moved over a distance several times greater than thickness of alveolar bony plates. b. Changes following application of extreme forces When extreme forces are applied to teeth—crushing or total compression of periodontal ligament occurs. On pressure side—root closely approximated lamina dura, compresses periodontal ligament and leads to occlusion of blood vessels. Ligament is deprived of its nutritional supply leading to regressive changes called hyalinization. In this case bone cannot resorb in the frontal portion adjacent to the teeth; rather bone resorption occurs in adjacent marrow spaces and in the alveolar plate below, behind and above the hyalinized zones. This kind of resorption is called as undermining resorption or rearward resorption. On tension side—periodontal ligament is overstretched leading to tearing of blood vessels and ischaemia. When extreme force is applied during orthodontic tooth movement, there is a net ↑ in osteoclastic activity as compared to bone formation, with result the tooth becomes loosened in its socket. Pain and hyperaemia of the gingiva may occur. Hyalinization: It is a form of tissue degeneration characterized by formation of a clear, eosinophilic, homogenous substance. Conventional process of hyalinization is an irreversible process, whereas hyalinization of periodontal ligament is a reversible process. During almost all the forms of orthodontic tooth movement, hyalinization of periodontal ligament on the pressure side occurs in some areas. These areas are wider when force is applied to extreme. Orthodontics-Part-I-2013.indd 134 Changes observed during formation of hyalinized zones are as follows: There is a gradual shrinkage of periodontal ligament fibres. Cellular structures become indistinct; some nuclei become smaller (pycnotic) while some nuclei disappear. Compressed collagenous fitness gradually unites into a more or less cell-free mass. Certain changes occur in ground substance. There is a breakdown of blood vessel walls, leading to spilling of their contents. Osteoclasts formed in marrow spaces and adjacent areas of inner bone surface after a period of 20–30 hours. Presence of hyalinized zone Periodontal ligament is non-functional, and bone resorption cannot occur. Tooth is not capable of further movement until local damaged tissue is removed and adjacent alveolar bone wall resorbs. Elimination of hyalinized zone The two mechanisms involved are: i. Resorption of bone by osteoclasts differentiating in peripheral intact periodontal ligament and in adjacent marrow spaces. ii. Invasion of cells and blood vessels from the periphery of compressed zone by which necrotic tissue is removed by enzymatic action and phagocytosis. Greater the force, wider the areas of hyalinization— large areas of periodontal ligament become functionless, thereby showing large areas of rearward resorption. Light forces—hyalinized zones are smaller—large areas of functional ligament is available and frontal resorption predominates in case of lighter forces. Nature of tooth movement and location of hyalinized tissue (a) (b) (c) Fig. 14.2 Nature of tooth movement and location of hyalinized tissue. (a) Tipping tooth movement—hyalinization close to alveolar crest, (b) Bodily tooth movement—hyalinization close to mid portion of root, (c) Excessive force applied during tipping—two areas of hyalinization: one in apical and one in marginal area. 12/3/2013 2:49:21 PM
  • Topic wise Solved Questions of Previous Years 135 Tipping tooth movement—hyalinization close to alveolar crest. Bodily tooth movement—hyalinization close to mid portion of root. Excessive forces applied during tipping—two areas of hyalinization—one in apical and one in marginal area. Areas of bony prominences and spicules usually result in areas of hyalinization. Q. 2. What are the theories of tooth movement? What factors affect the tooth movement? Or What are different theories of tooth movement? Discuss the pressure–tension theory in detail. Or Describe the blood flow theory of tooth movement. Or What are the various theories that are involved in the biology of orthodontic tooth movement? Discuss in detail. Ans. Certain theories have been put forward to explain mechanism of movement of a tooth by an orthodontic force. Accepted theories are as follows: i. Pressure–tension theory—Schwarz (1932) ii. Fluid dynamic theory or blood flow theory—Bein iii. Bone bending piezoelectric theory—Farrar (1876). i. Pressure–tension theory According to Schwarz, whenever a tooth is subjected to orthodontic force it results in the areas of pressure and tension. The area of periodontium in the direction of tooth movement is under pressure, shows bone resorption. The area of periodontium opposite to tooth movement is under tension, shows bone deposition. ii. Fluid dynamic theory This theory is also called blood flow theory, as proposed by Bein. According to this theory, tooth movement occurs as a result of alterations in fluid dynamics in periodontal ligament. Periodontal ligament occupies periodontal space between the tooth and alveolar socket. Periodontal space consists of fluid system made of interstitial fluid, cellular elements, blood vessels, viscous ground substance in addition to periodontal fibres. When a force of greater magnitude and direction is applied during orthodontic tooth movement, the interstitial fluid Orthodontics-Part-I-2013.indd 135 in periodontal ligament squeezes out and moves towards apex and cervical margins, and results in decreased tooth movement. It was termed squeeze film effect by Bien. When orthodontic force is applied, it results in the compression of periodontal ligament. Blood vessels of periodontal ligament are trapped between principal fibres resulting in their ‘stenosis’. The vessel above stenosis then balloons, resulting in the formation of ‘aneurysm’ (which are minute walled sacs of fluid). Bien suggested that there is an alteration in the chemical environment at the site of vascular stenosis due to decreased O2 level in the compressed area as compared to tension side. The formation of these aneurysms and vascular stenosis causes blood gases to escape into the interstitial fluid, thereby creating a favourable local environment for resorption. iii. Bone bending and piezoelectric theories of tooth movement Farrar (1876) first noted the deformation or bending of interseptal alveolar walls. He was the first to suggest that bone bending may be the possible mechanism for bringing about tooth movement. Piezoelectricity is a phenomenon observed in many crystalline materials in which a deformation of the crystal structure produces a flow of electric current as a result of displacement of electrons from one part of the crystal lattice to the other. A small electric current is generated when bone is mechanically deformed. The possible sources of electric current are: i. Collagen ii. Hydroxyapatite iii. Collagen–hydroxyapatite interface (the junction between the collagen and hydroxyapatite crystals when bent can be a source of piezoelectricity) iv. Mucopolysaccharide fraction of ground substance is not crystalline but may also possess the ability to generate electric current when deformed. When crystal structure is deformed, the electrons migrate from one location to another, resulting in electric charge. When force is released, the crystals return to their original shape and a reverse flow of electrons is observed. It has two unusual characteristics: i. Quick decay rate: This piezoelectric signal quickly dies away to zero, even though the force is maintained. ii. When the force is released, electron flow in the opposite direction is seen. On application of force on a tooth, the adjacent alveolar bone bears the following: i. Areas of concavity in bone associated with negative charge evoke bone deposition ii. Areas of concavity associated with positive charge evoke bone resorption 12/3/2013 2:49:21 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 136 On application of force, alveolar and medullary cortical plates of bone move together closely. Bone becomes less concave and electrical signal associated with resorption is established. The bone which is deformed by stress becomes electrically charged. Concave surfaces attain negative polarity and convex surfaces a positive polarity. As a result of these electrical signals, a remodelling response is evoked, bone is added to concave surfaces and resorbed from convex surfaces. Q. 3. What are different types of tooth movement? Ans. Different types of orthodontic tooth movement are: i. Tipping ii. Pure translation iii. Root movement iv. Rotation. i. Tipping Tipping is the simplest type of tooth movement that can easily be carried out with the application of a single force to the crown. It is of two types: a. Uncontrolled tipping b. Controlled tipping. a. Uncontrolled tipping Uncontrolled tipping is produced when a single force is applied to the crown of a tooth, where the crown moves in one direction and the root moves in opposite direction. In uncontrolled tipping the centre of rotation is in between the centre of resistance and apex of the root. Force required is 35–60 g. The distribution of load is such that the periodontal ligament is stressed near the apex on the same side as the applied force and at the crest of the alveolar bone on the opposite side. It is useful when incisors have to be proclined. b. Controlled tipping This is a desirable tooth movement as compared to uncontrolled tipping. Centre of rotation is at the root apex—the crown moves in one direction and there is minimal or no movement of the root in opposite direction. Force required is same as that of uncontrolled tipping in the range of 35–60 g. Minimum stress of the periodontal ligament at root apex. This prevents root movement. It is useful in retraction of excessively proclined incisors when roots are normally positioned. Orthodontics-Part-I-2013.indd 136 ii. Pure translation In translation, crown and root move in the same direction to the same distance. When two forces are applied simultaneously to the crown of the tooth, the applied force passes through the centre of resistance and translation of a tooth occurs. Pure translation is of three types: a. Bodily movement b. Intrusion c. Extrusion. a. Bodily movement This is the most desirable type of tooth movement. In bodily movement, crown and root move to the same distance in same direction either lingually or labially. The force applied is 70–120 g and the centre of rotation is at infinity. Uniform stress pattern is seen in the periodontal ligament. b. Intrusion It is defined as the axial movement of the tooth along the long axis towards the apex of the root. This tooth movement requires minimum force and centre of rotation passes through the centre of resistance. 10–20 g of force is required and the periodontal ligament at the apex is compressed over a small area and no areas of tension exist. c. Extrusion It is defined as the axial movement of the tooth along the long axis towards the coronal part. 35–60 g of force is required. No areas of compression in periodontal ligament; only stretched areas are seen. iii. Root movement This is the opposite of crown tipping and crown of a tooth is kept stationary, while the root moves labiolingually or mesiodistally. Root movement is mainly used to torque the incisor and upright the tipped teeth. There are two types of root movement: a. Torque b. Uprighting. a. Torque Labiolingual root movement is known as torque. b. Uprighting This is nothing but mesiodistal root movement with centre of rotation at the incisal edge. 50–100 g of force is required. The stress is greatest at the apex and decreases gradually to the cervical level. 12/3/2013 2:49:21 PM
  • Topic wise Solved Questions of Previous Years 137 iv. Rotation Spinning of the tooth around its long axis or A displacement of the body, produced by a couple of force characterized by the centre of rotation coinciding with the centre of resistance is known as rotation. Pure rotations can be divided into two types: a. Transverse rotation: The tooth displacement during which the long-axis orientation changes is known as transverse rotation. Example: Tipping and torquing. b. Long-axis rotation: In this type of tooth displacement, the angulation of the long axis is not altered. Example: Rotation of a tooth around its long axis. Generalized rotation: Any movement that is not pure translation or rotation can be described as a combination of both translation and rotation is called generalized rotation. This type of movement can be seen during routine clinical practice. Q. 4. Discuss biochemical principles involved in orthodontic tooth movement and add a note on undermining resorption. Ans. When orthodontic force is applied onto a tooth, it results in a number of biophysical events such as compression of periodontal ligament, bone deformation and tissue injury. Decreased vascularity and overstretching of periodontal ligament induces chemical changes and inflammatory type of response is elicited. The biophysical events in turn lead to certain biochemical reactions at a cellular level, which bring about the release of some extracellular signalling molecules called first messengers. These include hormones such as PTH, local chemical mediators such as prostaglandins, and neurotransmitters such as substance P and vasoactive intestinal polypeptide (VIP). First messengers Prostaglandin becomes the first messengers. Prostaglandin E plays a major role in the cellular differentiation. Other first messengers are parathormone (PTH), substance P, vasoactive peptides. These bind to the cell surface receptors and activate the extracellular signals. Second messengers Conversion of extracellular signal into an intracellular signal is the next step in cellular differentiation. The first messengers bind to receptors present on the cell surface of target cells and initiate a process of intracellular signalling. The conversion of extracellular into intracellular signal takes place by two pathways: i. Conversion of ATP into cyclic AMP ii. Opening of calcium ion channel and activate Ca++. The intracellular signalling results in the formation of second messengers, which include cAMP, cyclic GMP and calcium. The formation of second messengers inside the cells is believed to initiate formation of bone cells, namely, osteoclasts and osteoblasts, which are responsible for bone remodelling. It takes nearly 4 hours of sustained pressure to produce second messengers; hence any appliance, therefore, has to be worn for a minimum period of 4–6 hours to produce effects. Third messengers Within the cells the cAMP and Ca++ act on the protein kinase enzymes, which are the third messengers. Protein kinase causes phosphorylation of the cells. Phosphorylation results in differentiation and activation of osteoclasts and osteoblasts, which ultimately produce bone remodelling. As the remodelling of bony socket starts, the tooth movement begins. SHORT ESSAYS Q. 1. Explain frontal resorption. Ans. Frontal resorption is a type of tissue change at pressure zone in orthodontic tooth movement following application of light force. Frontal resorption is also called periosteal resorption or direct resorption or forward resorption. Orthodontics-Part-I-2013.indd 137 Changes on pressure side (tooth movement side) are as follows: Periodontal ligament compressed to one-third of its original thickness. Marked ↑ in vascularity of periodontal ligament due to ↑ capillary blood supply—mobilization of cells, fibroblasts and osteoclasts. Osteoclasts lie in shallow depressions of bone called Howship’s lacunae. They start resorbing bone. 12/3/2013 2:49:21 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 138 When the forces applied are within physiologic limits, the resorption is seen in the alveolar plate immediately adjacent to the ligament. This kind of resorption is called frontal resorption. In frontal resorption, the resorption process is initiated from the periodontal ligament side of the alveolar bone. Frontal resorption usually takes place after 2 days following orthodontic force application. Q. 2. Response of bone and periodontium to orthodontic force at tension zone Ans. The response of bone and periodontium at tension zone on application of orthodontic force is as follows: As compared to pressure zone the cellular activity is delayed in areas of tension. It takes around 30 hours for increased cellular activity to be seen in tension zone. The stretched periodontal fibres are reconstructed by changes of the original fibrils. In the areas of tension, macrophages are found in great numbers and there is inflammatory-type change like breakdown and rebuilding of fibrous elements. Around the parts of the fibres that are close to the alveolar wall-new unmineralized matrix is laid down. After some time, osteoid is laid on the whole of the alveolar wall on the tension side. Osteoblasts synthesize the osteoid. Subsequently mineralization of osteoid takes place. Rate of bone deposition is about 30 µm per day. Q. 3. Enumerate the various types of tooth movement. Or What is bodily tooth movement? Ans. Various types of orthodontic tooth movement are: i. Tipping a. Controlled tipping b. Uncontrolled tipping. ii. Pure translation a. Bodily movement b. Intrusion c. Extrusion. iii. Root movement a. Torque b. Uprighting. iv. Rotation. Bodily movement Bodily movement is a type of pure translation. Orthodontics-Part-I-2013.indd 138 In translation, crown and root move in the same direction to the same distance. When two forces are applied simultaneously to the crown of the tooth, the applied force passes through the centre of resistance and translation of a tooth occurs. This is the most desirable type of tooth movement. In bodily movement, crown and root move to the same distance in same direction either lingually or labially. The force applied is 70–120 g and the centre of rotation is at infinity. Uniform stress pattern is seen in the periodontal ligament. Q. 4. Undermining resorption Ans. Undermining resorption is also known as indirect resorption. The term ‘undermining resorption’ was coined by Sandstedt. This is a type of tissue change at pressure zone in orthodontic tooth movement following application of heavy force. When extreme forces are applied to teeth, crushing or total compression of periodontal ligament occurs. On pressure side, root closely approximates lamina dura, compresses periodontal ligament and leads to occlusion of blood vessels. Ligament is deprived of its nutritional supply leading to regressive changes called hyalinization. Once hyalinization occurs in the periodontal ligament, frontal resorption is not possible. In this case, bone cannot resorb in the frontal portion adjacent to the teeth; rather bone resorption occurs in adjacent marrow spaces and in the alveolar plate below, behind and above the hyalinized zones. This kind of resorption is called undermining resorption or rearward resorption. When extreme force is applied during orthodontic tooth movement, there is a net ↑ in osteoclastic activity as compared to bone formation, with result the tooth becomes loosened in its socket. This method of resorption is called undermining resorption because the attack is from the underside of lamina dura. Q. 5. Enumerate various phases of tooth movements. Ans. Burstone categorized the phases of tooth movement as follows: Three phases of tooth movement are: i. Initial phase ii. Lag phase iii. Post-lag phase. 12/3/2013 2:49:21 PM
  • Topic wise Solved Questions of Previous Years 139 i. Initial phase Very rapid tooth movement occurs over a short distance and then stops. This movement represents displacement of tooth in periodontal ligament space and probably bending of alveolar bone to certain extent. Both light and heavy forces displace tooth to same extent. In this phase, tooth movement is between 0.4 and 0.9 mm in a week’s time. ii. Lag phase This phase represents the period of hyalinization characterized by formation of hyalinized tissue in periodontal ligament. During this phase, little or no tooth movement occurs. Duration of lag phase depends upon the amount of force used to move the tooth, usually extends up to 14 days. When light forces are applied, areas of hyalinization are small, frontal resorption occurs, and the duration of lag phase will be lesser. When heavy forces are applied, areas of hyalinization are large, rearward resorption occurs, and the duration of lag phase to eliminate hyalinized tissue will be longer. iii. Post-lag phase Tooth movement progresses rapidly as the hyalinized zone is removed, and bone resorption occurs directly facing periodontal ligament. Periodontal ligament is widened. SHORT NOTES Q. 1. Ideal orthodontic force Or Optimum orthodontic force Ans. Ideal or optimum orthodontic force is the one that moves the teeth most rapidly in desired direction with least possible damage to the tissue and minimum patient discomfort. Optimum orthodontic force = capillary pulse pressure, i.e. 20–26 g/cm2 of root surface area. From clinical point of view, it produces rapid tooth movement with minimum patient discomfort and minimum lag phase, and no marked mobility of teeth being moved. From histological point of view, vitality of tooth and supporting periodontal ligament is maintained and produces direct frontal resorption. Q. 2. Name the theories of tooth movement. Ans. Certain theories have been put forward to explain mechanism of movement of a tooth by an orthodontic force. Accepted theories are as follows: i. Pressure–tension theory—Schwarz (1932) ii. Fluid dynamic theory or blood flow theory—Bein iii. Bone bending piezoelectric theory—Farrar (1876). Q. 3. Types of orthodontic force Ans. Orthodontics-Part-I-2013.indd 139 Based on the duration and decay rate of orthodontic force, it is classified by Proffit as: i. Continuous force ii. Interrupted force iii. Intermittent force. i. Continuous force In this type, between the two successive visits of the patient, force is maintained at some appreciable fraction of the original force. The force level does not decline to zero. For the continuous force to be effective, it has to be a light continuous force. ii. Interrupted force In this type of force, the force level reduces to zero between the two successive visits of the patient. Both light and heavy interrupted forces are clinically acceptable, e.g. fixed appliance. iii. Intermittent force In this type of force, there is a sudden drop of force to zero level when the orthodontic appliance is removed by the patient. Intermittent force acts as an impulse or a shock for short periods with a series of interruptions. Example: Functional appliances. Q. 4. Piezoelectric theory Ans. Bone bending and piezoelectric theories of tooth movement was proposed by Farrar (1876). 12/3/2013 2:49:21 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 140 He was the first to suggest that bone bending may be possible mechanism for bringing about tooth movement. Piezoelectricity is a phenomenon observed in many crystalline materials in which a deformation of the crystal structure produces a flow of electric current as a result of displacement of electrons from one part of the crystal lattice to the other. A small electric current is generated when bone is mechanically deformed. Bone and collagen both have piezoelectric property. Q. 5. Undermining resorption Ans. Undermining resorption is also known as indirect resorption. This is a type of tissue change at pressure zone in orthodontic tooth movement following application of heavy force. Once hyalinization occurs in periodontal ligament, frontal resorption is not possible. In this case, bone cannot resorb in the frontal portion adjacent to the teeth; rather bone resorption occurs in adjacent marrow spaces and in the alveolar plate below, behind and above the hyalinized zones. This kind of resorption is called undermining resorption or rearward resorption. This method of resorption is called ‘undermining resorption’ because the attack is from the underside of lamina dura. Q. 6. Explain frontal resorption. Ans. Frontal resorption is a type of tissue change at pressure zone in orthodontic tooth movement following application of light force. Frontal resorption is also called periosteal resorption or direct resorption or forward resorption. When the forces applied are within physiologic limits, the resorption seen in the alveolar plate immediately becomes adjacent to the ligament. This kind of resorption is called frontal resorption. Frontal resorption usually takes place after 2 days following orthodontic force application. Q. 7. Interrupted force Ans. Interrupted force is a type of orthodontic force. In this type of force, the force level reduces to zero between the two successive visits of the patient. Both light and heavy interrupted forces are clinically acceptable, e.g. fixed appliance. Orthodontics-Part-I-2013.indd 140 Q. 8. Physiologic tooth movement Ans. Physiologic tooth movement designates primarily the slight tipping of the functioning tooth in its socket and secondarily, the changes in tooth position that occur in young people during and after tooth eruption. It is of three types: i. Movement during mastication ii. Eruption of tooth iii. Tooth migration. i. Movement during mastication During chewing, the teeth tip slightly around the neutral axis as fulcrum and are displaced because of bending of the alveolar process also. Movement during mastication is transient. ii. Eruption of tooth Different teeth move in different directions during eruption. iii. Migration of teeth Migration of teeth is a slow tooth movement usually in mesial and occlusal directions. These movements take place to compensate for interproximal attrition and occlusal wear. Q. 9. Centre of resistance Ans. Centre of resistance is defined as the point in the object at which the resistance to movement is at the maximum. The centre of resistance of tooth is variable. It depends on the following: i. Root morphology ii. Number of roots iii. Level of alveolar bone support iv. Root length. Application of force to the centre of resistance of the tooth produces true bodily movement. Q. 10. Root resorption Ans. Root resorption is more evident when heavy orthodontic forces are applied. Excessive force and prolonged duration of treatment increase the chances for resorption. Types of resorption: (i) generalized and (ii) localized resorptions. Most of the teeth exhibit some loss of root after orthodontic treatment. There is generalized shortening of root seen in majority of orthodontic patients. Orthodontic treatment causes severe localized resorption. Maxillary incisors are more prone for resorption. 12/3/2013 2:49:21 PM
  • Topic wise Solved Questions of Previous Years 141 One of the most important causes of root resorption in anteriors and molars is pressing of the roots against the cortical plate. Root resorption index: i. Grade I: Irregular root contour ii. Grade II: Root resorption <2 mm at the apex iii. Grade III: Root resorption 2 mm to one-third of root length iv. Grade IV: Root resorption >one-third of root length. Q. 11. Blood flow theory to explain tooth movement. Ans. Fluid dynamic theory is also called blood flow theory, as proposed by Bein. According to this theory, tooth movement occurs as a result of alterations in fluid dynamics in periodontal ligament. When orthodontic force is applied, it results in the compression of periodontal ligament. Blood vessels of periodontal ligament are trapped between principal fibres, resulting in their ‘stenosis’. The vessel above stenosis then balloons resulting in the formation of ‘aneurysm’. Bien suggested that there is an alteration in the chemical environment at the site of vascular stenosis due to decreased O2 level in the compressed area as compared to tension side. The formation of these aneurysms and vascular stenosis causes blood gases to escape into the interstitial fluid, thereby creating a favourable local environment for resorption. Q. 12. Intrusion Ans. Intrusion is defined as the axial movement of the tooth along the long axis towards the apex of the root. This tooth movement requires minimum force and the centre of rotation passes through the centre of resistance. 10–20 g of force is required and the periodontal ligament at the apex is compressed over a small area, and no areas of tension exist. Uniform stress pattern is seen in the periodontal ligament. Q. 14. Define force Ans. Force is a load or external influence applied to a body that changes or tends to change the position of that body. It is measured in grams or ounces. Types of force: i. Compression ii. Tension iii. Shear force. Q. 15. Name various types of tooth movement. Ans. Various types of orthodontic tooth movement are: i. Tipping a. Controlled tipping b. Uncontrolled tipping. ii. Pure translation a. Bodily movement b. Intrusion c. Extrusion. iii. Root movement a. Torque b. Uprighting. iv. Rotation. Q. 16. Force and couple Ans. Force is a load or external influence applied to a body that changes or tends to change the position of that body. Being a vector, force has a definite magnitude, a specific direction and a point of application. Couple is a pair of concentrated forces having equal magnitude and opposite direction with parallel but non-collinear line of action. A couple when acts upon a body brings about pure rotation. Q. 17. Write three advantages of optimum orthodontic force. Q. 13. Bodily movement Ans. Ans. The advantages of optimum orthodontic force are as follows: Efficient tooth movement is possible. Resorption is mainly of the frontal type. Elimination of lag phase and hyalinized zone. Less amount of pain and no damage to the supporting structures. Chances for root resorption are minimal. Bodily movement is a pure translational movement. This is the most desirable type of tooth movement. In bodily movement, crown and root move to the same distance in same direction either lingually or labially. The force applied is 70–120 g and the centre of rotation is at infinity. Orthodontics-Part-I-2013.indd 141 12/3/2013 2:49:21 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 142 Topic 15 ANCHORAGE LONG ESSAYS Q. 1. Define anchorage. Explain in detail about different types of anchorage with examples. Define orthodontic anchorage. Classify them. Discuss the uses of extraoral anchorage in orthodontics. Ans. Or Define anchorage. Classify orthodontic anchorage and explain with examples. Graber defined anchorage as ‘the nature and degree of resistance to displacement offered by an anatomic unit when used for the purpose of effecting tooth movement’. Proffit defines anchorage as resistance to unwanted tooth movement. Or Define anchorage. Discuss classification of anchorage. Explain intermaxillary anchorage. Or CLASSIFICATION OF ANCHORAGE Moyer has classified anchorage in the following ways: 1. According to manner of force application a. Simple anchorage b. Stationary anchorage c. Reciprocal anchorage 2. According to jaws involved a. Intramaxillary (anchorage from the same jaw) b. Intermaxillary (anchorage from both jaws) 3. According to site of anchorage a. Intraoral (anchorage from the same jaw) i. Intramaxillary b. Extraoral c. Muscular (anchorage from both jaws) ii. Intermaxillary • Simple • Stationary • Reciprocal i. Cervical ii. Cranial iii. Occipital iv. Facial 4. According to number of anchorage units a. Single (or) primary anchorage (anchorage involving one tooth) Orthodontics-Part-I-2013.indd 142 b. Compound anchorage (multiple teeth) c. Reinforced anchorage 12/3/2013 2:49:21 PM
  • Topic wise Solved Questions of Previous Years 143 The various types of anchorage are discussed in detail below: I. According to manner of force application a. Simple anchorage b. Stationary anchorage c. Reciprocal anchorage. a. Simple anchorage It is the ‘dental anchorage in which manner and application of force is such that it tends to change the axial inclination of the tooth or teeth that form the anchorage unit’. The simple anchorage is nothing but the resistance of the anchorage unit to tipping. The combined root surface area of the teeth forming the anchorage unit must be doubled to that of the teeth to be moved. The simple anchorage has the low resistance value. b. Stationary anchorage Stationary anchorage is defined as ‘dental anchorage in which the manner and application of force tends to displace the anchorage unit bodily’. Simply the resistance to bodily movement is called stationary anchorage. An anchor tooth or source that does not move against the forces of teeth to be pulled is stationary anchorage. Examples: ❍ Retraction of maxillary incisors using molars as anchor teeth. ❍ In real sense, only extraoral source of anchorage derived from headgears would be best example of stationary anchorage. c. Reciprocal anchorage The reciprocal anchorage is said to exist when two teeth or two sets of teeth move to an equal extent in opposite directions. In reciprocal anchorage the force applied for tooth movement is dissipated to both active and reactive components and the desired tooth movement occurs by movement of both the units. Teeth may need to be pulled against each other to close the spaces. Examples: ❍ Closure of midline diastema ❍ Use of crossbite elastics to correct single tooth crossbite and class II malocclusion with intermaxillary elastics ❍ Dental arch expansion. II. According to jaws involved a. Intramaxillary (anchorage from the same jaw) b. Intermaxillary (anchorage from both jaws). Orthodontics-Part-I-2013.indd 143 a. Intramaxillary anchorage When all the anchorage units as well as the teeth to be moved are situated within the same jaw, the anchorage is described as intramaxillary anchorage. The appliances are placed in only one jaw, either maxilla or mandible. It may be simple, stationary or reciprocal type of resistance. Example: Elastic chains used to retract the anterior segment using the posterior teeth as anchorage units. b. Intermaxillary anchorage It is also known as Baker’s anchorage. When the anchorage units situated in one jaw are used to bring about tooth movement in the opposing jaw, the anchorage is called intermaxillary anchorage. Example: ❍ Class II elastics worn from mandibular molars to maxillary anteriors, which are used to retract the maxillary anteriors. ❍ Class III elastics worn from maxillary molars to mandibular anteriors are used to retract the mandibular anteriors. III. According to site of anchorage a. Intraoral b. Extraoral c. Muscular. a. Intraoral anchorage Intraoral anchorage is classified as: i. Intramaxillary ii. Intermaxillary Intraoral anchorage is an anchorage in which all the anchorage units are situated inside the oral cavity. The various sources of intraoral anchorage are: i. Teeth ii. Palate iii. Lingual alveolar bone of the mandible. When all the anchorage units as well as the teeth to be moved are situated within the same jaw, it is described as intramaxillary anchorage. When the anchorage units situated in one jaw are used to bring about tooth movement in the opposing jaw the anchorage is called intermaxillary anchorage. Example: correction of class II and class III malocclusions using intermaxillary elastics. b. Extraoral anchorage Extraoral anchorage is an anchorage situation wherein the anchorage units are situated outside the oral cavity. Various types of extraoral anchorage are: i. Cervical ii. Cranial 12/3/2013 2:49:21 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 144 iii. Occipital iv. Facial. It is also used as a form of reinforced anchorage. Extraoral anchorage is usually used to correct skeletal problems. The various extraoral sources of anchorage are headgear, face mask, chin cup, etc. Various sites of extraoral anchorage with examples: i. Occipital region: Chin cap and high-pull headgear ii. Parietal: Combination headgear iii. Forehead: Reverse-pull headgear iv. Back of neck: Cervical headgear v. Chin: Reverse-pull headgear and chin cap. c. Muscular anchorage Muscular forces can be used for anchorage purpose. Muscular forces when redirected to a favourable action on the teeth serve as a source of anchorage. Example: Vestibular shield and lip bumper. A lip bumper transmits the force of hyperactive lower lip to molars, aiding in its uprighting. iv. According to number of anchorage units a. Single (or) primary anchorage (anchorage involving one tooth) b. Compound anchorage (anchorage involving multiple teeth) c. Reinforced anchorage. a. Single or primary anchorage In primary anchorage, the resistance provided by a single tooth with greater alveolar support is used to move the tooth with less alveolar support. Example: Moving a tooth with smaller root surface area against a tooth with large root surface area, which is called an anchor. b. Compound anchorage In this, the resistance provided by more than one tooth with greater support is used to move teeth with lesser support. c. Reinforced anchorage It is also known as multiple anchorage. The anchorage where more than one resistance unit is utilized is called as reinforced anchorage. When more units are added, resistance units become more effective because reactionary force is distributed over a large area. By distribution of force over a large area and keeping the force light, trauma and pain during treatment are minimized. Orthodontics-Part-I-2013.indd 144 Example: ❍ Use of transpalatal arch, translingual arch and Nance space holding buttons reinforces the anchorage unit ❍ Usage of headgears ❍ In cases with upper anterior bite plane, use of labial bow to prevent flaring of the upper incisors is another example of reinforced anchorage. ❍ Sved-type bite plates. v. Other types of anchorage a. Cortical bone or cortical anchorage Cortical bone offers more resistance to resorption than medullary bone. The response of cortical bone when compared to medullary bone is different. If the roots are torqued lingually or buccally, the resistance to movement is increased; this principle is being used by rickets and is called cortical anchorage. Example: Space closure in old extraction site is difficult as the roots encounter cortical bone along the residual ridge. b. Implants as anchorage Recently implants are being used as anchorage units. They have been designed exclusively for orthodontic purpose. Various orthodontic implants are onplant, orthosystem implant, Aarhus implants and mini implants. Onplant is a disc-like structure that can be placed under local anaesthesia on the posterior aspect of hard palate. Orthosystem implant is a screw-type endosteal implant of about 4–6 mm in length. Aarhus implant is very small in size and early loading is possible, hence are used in multiple sites between roots. Mini implants are very small—1.2 × 6 mm in dimension. Uses of implants: ❍ Implants serve as a source of absolute anchorage. Example: Retromolar implant anchorage for closing of edentulous space in first molar extraction sites. ❍ These are used for anchorage and as abutments for restorations. ❍ Implants are also used in distraction osteogenesis. Q. 2. Define reinforced anchorage. Discuss methods of reinforcing anchorage. Or Classify anchorage. Explain when, why and how would you like to reinforce it. Ans. 12/3/2013 2:49:21 PM
  • Topic wise Solved Questions of Previous Years 145 Reinforced anchorage is also known as multiple anchorage. The anchorage where more than one resistance unit is utilized is called as reinforced anchorage. Reinforced anchorage refers to the augmentation of anchorage by various means like extraoral appliances, upper anterior inclined plane or a transpalatal arch. Extraoral forces, i.e. forces generated from extraoral areas such as cranium, back of the neck and face can be used to reinforce the anchorage. When more units are added, resistance units become more effective because reactionary force is distributed over a large area. By distribution of force over a large area and keeping the force light, trauma and pain during treatment are minimized. Multiple anchorage is the augmentation of anchorage by various methods like fixed appliances, rigid labial bow, Sved-bite planes, intermaxillary anchorage and use of extraoral anchorage. Examples: i. Use of transpalatal arch, translingual arch and Nance space holding buttons reinforce the anchorage unit. a. Transpalatal arch: This is a wire that spans the palate in a transverse direction connecting the permanent upper first molars on either side with an omega loop in the midline. It is used in fixed mechanotherapy to augment anchorage. It is effective as an anchorage maintenance device as well as active orthodontic appliance. b. Translingual arch: It is used in mandible and functions as anchorage device. It is usually made up of 0.036 inch stainless steel wire extending along lingual contour of the mandibular dentition from first molar on one side to the opposite side of the jaw. c. Nance palatal arch: It is used in the upper arch as an anchorage device during levelling and alignment, in molar distalization cases and as a space maintainer. ii. Tissue- and tooth-borne anchorage such as palatal removable appliances with clasps of molar bands. iii. Upper anterior inclined plane: A removable appliance incorporating an upper anterior inclined plane results in forward glide of the mandible during closure of the jaw. This results in stretching of the retractor muscles of the mandible, which subsequently contracts and forces the mandible against the upper inclined plane. Thus, a distal force is applied on the maxillary teeth, thereby reinforcing maxillary anchorage. iv. Usage of headgears to augment the resistance unit. Orthodontics-Part-I-2013.indd 145 v. In cases with upper anterior bite plane, use of rigid labial bow to prevent flaring of the upper incisors is another example of reinforced anchorage. vi. Similarly, instead of a labial bow the acrylic plate is constructed in such a way that it covers the labial incisal aspect of maxillary incisors, which also prevents the labial flaring of the maxillary incisors. This type of reinforced anchorage is called Sved-type bite plates. vii. The anchorage may be reinforced in the case of fixed appliances by designing the appliance so that only bodily movement of the anchorage teeth can occur. Example: Passing a bow wire through the horizontal tube on bands attached to the adjacent teeth. Q. 3. Define and discuss the various anchorage situations in removable and fixed appliances. Ans. Graber defined anchorage as ‘the nature and degree of resistance to displacement offered by an anatomic unit when used for the purpose of effecting tooth movement’. Proffit defines anchorage as resistance to unwanted tooth movement. Anchorage sources for removable appliance: Removable appliances derive their anchorage from oral tissues and teeth in the following manner: Tissue-born anchorage The acrylic base plate, which is the major component of removable appliance, derives anchorage from tissue contact against palate and lingual surface of mandible. The acrylic base plate, which extends into the interdental spaces and embrasures, also secures the plate in situ. The base plate transmits the force all over the dentition as well as to the underlying hard and soft tissues. Modifications of base plate such as bite planes also reinforce anchorage by transmitting muscular forces to the jaws. The removable appliance also derives anchorage from clasps, pin heads, which securely fit on the teeth. These provide retention and help in the distribution of force. Anchorage sources for fixed appliances The major sources of anchorage in the fixed appliances are the teeth themselves. Fixed appliances entail heavy burden on the anchor teeth. Anchor units need to be supported either with incorporation of more teeth or support from cranium using headgears or modification of biomechanics—the so called anchorage savers. 12/3/2013 2:49:21 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 146 SHORT ESSAYS Q. 1. Define anchorage. Write Nanda’s classification of anchorage. Ans. Graber defined anchorage as ‘the nature and degree of resistance to displacement offered by an anatomic unit when used for the purpose of effecting tooth movement’. Proffit defines anchorage as resistance to unwanted tooth movement. Nanda’s classification of anchorage Depending on how much anchorage unit contributes to extraction space closure, Nanda classified the anchorage into three categories: i. Group A ii. Group B iii. Group C. i. Group A space closure 100–75% space closure from anterior retraction and 25% closure from posterior anchorage movement. There is a critical posterior anchorage. ii. Group B space closure It includes more equal amount of anterior and posterior tooth movement for space closure. It is an easy condition to deal with. iii. Group C space closure It includes 75–100% posterior protraction. There is a noncritical anterior anchorage and critical posterior anchorage. Anterior retraction is only 25%. This is a non-critical type of anchorage. Q. 2. Extraoral anchorage Ans. Extraoral anchorage is an anchorage situation wherein the anchorage units are situated outside the oral cavity. It is also used as a form of reinforced anchorage. Extraoral anchorage is usually used to correct skeletal problems. Extraoral anchorage is of following types: i. Cervical ii. Cranial iii. Occipital iv. Facial. The various extraoral sources of anchorage are: headgear, face mask, chin cup, etc. Orthodontics-Part-I-2013.indd 146 Various sites of extraoral anchorage with examples: i. Occipital region: Chin cap and high-pull headgear ii. Parietal: Combination headgear iii. Forehead: Reverse-pull headgear iv. Back of neck: Cervical headgear v. Chin: Reverse-pull headgear and chin cap. Q. 3. Reinforced anchorage Ans. Reinforced anchorage is also called multiple anchorage. This is an anchorage situation where more than one resistance unit is employed. Resistance units become more effective when more units are added because the reactionary force is distributed over a larger area. Distribution of force over a large area means keeping the force light, which minimizes trauma and pain during treatment. Examples: ❍ Use of transpalatal arch, Nance space holding buttons, lingual arch reinforces the anchorage unit. ❍ Usage of headgears to augment the resistance unit. ❍ The use of labial bow to prevent flaring of the upper incisors in cases where upper anterior bite plane is used is another example of reinforced anchorage. ❍ Sved-type bite plates: Instead of a labial bow, the acrylic plate is constructed in such a way that it covers the labial incisal aspect of maxillary incisors. This again prevents the labial flaring of the maxillary incisors. This type of reinforced anchorage is called Sved-type bite plates. Q. 4. Intermaxillary anchorage Ans. It is also known as Baker’s anchorage. When the anchorage units situated in one jaw are used to bring about tooth movement in the opposing jaw, the anchorage is called intermaxillary anchorage. Examples: ❍ Baker’s anchorage is a form of intermaxillary anchorage to adjust the jaw relationship and teeth by using elastics from maxilla to mandible. ❍ Class II elastics worn from mandibular molars to maxillary anteriors, which are used to retract the maxillary anteriors. ❍ Class III elastics worn from maxillary molars to mandibular anteriors are used to retract the mandibular anteriors. 12/3/2013 2:49:21 PM
  • Topic wise Solved Questions of Previous Years 147 Q. 5. Reciprocal anchorage Ans. The reciprocal anchorage is said to exist when two teeth or two sets of teeth move to an equal extent in an opposite direction. In reciprocal anchorage the force applied for tooth movement is dissipated to both active and reactive components and the desired tooth movement occurs by movement of both the units. Teeth may need to be pulled against each other to close the spaces. Examples: ❍ Closure of midline diastema: The midline diastema in the upper arch can be closed by tying them with tight elastic thread. ❍ Use of bite elastics to correct single-tooth crossbite. ❍ Correction of class II malocclusion with intermaxillary elastics. ❍ Dental arch expansion. SHORT NOTES Q. 1. Define anchorage. Or Anchorage in orthodontics. Or Define anchorage in orthodontics. Give White and Gardiner classification. Ans. Graber defined anchorage as ‘the nature and degree of resistance to displacement offered by an anatomic unit when used for the purpose of effecting tooth movement’. Proffit defines anchorage as resistance to unwanted tooth movement. White and Gardener’s classification of anchorage: i. Simple ii. Stationary iii. Reciprocal iv. Reinforced v. Intermaxillary vi. Extraoral. Q. 2. Extraoral anchorage Or Extraoral sources of anchorage Ans. Extraoral anchorage is an anchorage situation wherein the anchorage units are situated outside the oral cavity. It is also used as a form of reinforced anchorage and is usually used to correct skeletal problems. Various sites of extraoral anchorage with examples are: i. Occipital region: Chin cap and high-pull headgear ii. Forehead: Reverse-pull headgear Orthodontics-Part-I-2013.indd 147 iii. Back of neck: Cervical headgear iv. Chin: Reverse-pull headgear and chin cap. Q. 3. Reciprocal anchorage Ans. i. The reciprocal anchorage is said to exist when two teeth or two sets of teeth move to an equal extent in an opposite direction. ii. In reciprocal anchorage the force applied for tooth movement is dissipated to both active and reactive components and the desired tooth movement occurs by movement of both the units. iii. Examples: Closure of midline diastema, dental arch expansion and use of crossbite elastics. Q. 4. Intermaxillary anchorage Or Baker’s anchorage Ans. i. Intermaxillary anchorage is an anchorage situation in which anchorage unit situated in one jaw is used to bring about tooth movement in the opposite jaw. ii. Baker’s anchorage is a form of intermaxillary anchorage to adjust the jaw relationship and teeth by using elastics from maxilla to mandible. iii. Example: Correction of class II and class III malocclusion by using intermaxillary elastics. Q. 5. Stationary anchorage Ans. i. Stationary anchorage is defined as ‘dental anchorage in which the manner and application of force tends to displace the anchorage unit bodily’. 12/3/2013 2:49:21 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 148 ii. An anchor tooth or source that does not move against the forces of teeth to be pulled is stationary anchorage. iii. Examples: ❍ Retraction of maxillary incisors using molars as anchor teeth ❍ Extraoral source of anchorage derived from headgears. Q. 6. Simple anchorage Ans. It is the ‘dental anchorage in which manner and application of force is such that it tends to change the axial inclination of the tooth or teeth that form the anchorage unit’. The simple anchorage is nothing but resistance of the anchorage unit to tipping. The combined root surface area of the teeth forming the anchorage unit must be doubled to that of the teeth to be moved. The simple anchorage has the lowest resistance value. Q. 7. Define anchorage. Classify it with respect to number of teeth used. Ans. Graber defined anchorage as ‘the nature and degree of resistance to displacement offered by an anatomic unit when used for the purpose of effecting tooth movement’. Proffit defines anchorage as resistance to unwanted tooth movement. According to number of anchorage units: i. Single (or) primary anchorage (anchorage involving one tooth) ii. Compound anchorage (multiple teeth) iii. Reinforced anchorage. Q. 8. Define reciprocal anchorage. Give examples of reciprocal anchorage. Ans. In a reciprocal anchorage situation, the force applied for tooth movement is dissipated to both the active and reactive components. The dissipation of equal and opposite forces tends to move both the units toward each other. The desired tooth movement occurs by movement of both the units. Examples: ❍ Closure of median diastema by moving both the central incisors towards each other ❍ Corrections of class II malocclusion with intermaxillary elastics Orthodontics-Part-I-2013.indd 148 ❍ Corrections of single tooth crossbite through the bite elastic. Q. 9. Define anchorage. Enumerate methods of reinforcing anchorage. Or What is reinforced anchorage? Give two examples. Ans. The anchorage where more than one resistance unit is utilized is called as reinforced anchorage. Reinforced anchorage refers to the augmentation of anchorage by various means like extraoral appliances, upper anterior inclined plane or a transpalatal arch. Examples: ❍ Use of transpalatal arch, translingual arch and Nance space holding buttons reinforce the anchorage unit. ❍ Usage of headgears. ❍ In cases with upper anterior bite plane, use of labial bow to prevent flaring of the upper incisors is another example of reinforced anchorage. ❍ Sved-type bite planes. Q. 10. Cortical anchorage Ans. i. Cortical bone offers more resistant to resorption than medullary bone. The response of cortical bone when compared to medullary bone is different. ii. If the roots are torqued lingually or buccally, the resistance to movement is increased; this principle was used by Rickets and is called cortical anchorage. iii. Example: Space closure in old extraction site is difficult as the roots encounter cortical bone along the residual ridge. Q. 11. Factors affecting anchorage Ans. Factors affecting anchorage can be considered under following factors: a. Biological factors b. Mechanical factors. a. Biological factors include: i. Teeth ii. Size of the anchoring unit iii. Axial inclination of teeth iv. Use of optimum force v. Differential force system vi. Persistent habits vii. Anchorage savers. 12/3/2013 2:49:21 PM
  • Topic wise Solved Questions of Previous Years 149 b. Mechanical factors include: i. Friction ii. Type of tooth movement planned iii. Technique employed in retraction mechanics. Q. 12. Anchorage loss Ans. The undesirable movement of the anchor tooth in excess of that of the planned treatment is known as anchorage loss. Topic 16 Reasons for anchorage loss are: Excessive force Improper treatment planning and anchorage preparation Resistance between arch wires and brackets. Methods to prevent anchorage loss are: Use of anchorage savers like transpalatal arches, lingual arches, etc. Use of optimum and differential force Utilizing muscular forces Reinforcement of anchorage. AGE FACTORS IN ORTHODONTICS SHORT ESSAYS Q. 1. Age factors in orthodontics Or Difference between adult and adolescent patients Ans. Differences in orthodontic treatment for young and adult patients are as follows: Factor Young patients 1. Growth to Orthodontist has growth work with to work with, i.e. using growth potential of the patient most orthodontic and orthopaedic treatments can be efficiently carried out 2. Diagnosis Orthodontics-Part-I-2013.indd 149 Adult patients Due to lack of growth orthodontist merely relies on tooth movement or surgery Routine diagnostic aids Routine diagnoscan be used tic aids can be used and some dormant pathologies like impactions, periodontal problems, decay and loss of teeth can hamper the success of orthodontic treatment 3. Appliance These patients can benselection efited from orthopaedic and myofunctional appliances that help to modulate growth in case of growth abnormalities In these patients, the options are restricted to orthodontic tooth movement and surgery 4. Periodontal Less common problems More common 5. Patient mo- Not well-motivated and We l l - m o t i va te d and cooperate tivation and do not cooperate well well cooperation 6. Tissue vi- Tissue vitality and respon- Due to decreased tality siveness to force is much cellularity and vasgreater in children cularity the tissue vitality and responsiveness to force is not so much in adults 7. Treatment Achieved well objectives The orthodontist has to strike a best possible balance between various treatment objectives like function, stability and aesthetics 8. Treatment Less in young patients appreciation More in adult patients 12/3/2013 2:49:21 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 150 SHORT NOTES Q. 1. List the age factors in orthodontics. Ans. The list of various age factors considered in orthodontics are as follows: i. Utilization of growth potential to work with ii. Various diagnostic methods used iii. Selection of appliance iv. Periodontal problems v. Patient motivation and cooperation vi. Tissue vitality vii. Treatment objectives viii. Treatment appreciation. Q. 2. Ideal age for various orthodontic treatment Ans. The age of the patient influences orthodontic therapeutic interventions and prognosis. The effectiveness of functional appliances like twin block, bionator, Frankel appliance given for class II skeletal correction and orthopaedic appliances like headgears to correct maxillary prognathism are effective during growing stage of the patient. Topic 17 Maxillary expansion procedures are carried out before the fusion of palatal sutures during early adolescence. Orthognathic surgeries are best undertaken in adult patients after growth cessation. Q. 3. Adult orthodontics Ans. Orthodontic treatment of adults is known as adult orthodontics. Orthodontic treatment for adults is broadly classified into two types: 1. Adjunctive orthodontic treatment 2. Comprehensive orthodontic treatment. Adjunctive orthodontic treatment procedures are carried out to facilitate other dental procedures to control disease and restore function, e.g. uprighting of molars, forced eruption, crossbite correction, diastema closure, etc. Comprehensive orthodontic treatment is the essential treatment procedure carried out in children for correction of malocclusion. Response to orthodontic force is slightly slower in adults as compared to children. PREVENTIVE ORTHODONTICS LONG ESSAYS Q. 1. Define preventive orthodontics. Discuss the various treatment plans given under the preventive orthodontics. Ans. Graber defined preventive orthodontics as ‘the action taken to preserve the integrity of what appears to be a normal occlusion at a specific time’. Proffit and Ackerman defined it as ‘the prevention of potential interference with occlusal development’. Procedures undertaken in preventive orthodontics are as follows: A. Preventive procedures without use of appliances i. Predental procedures and parental education Orthodontics-Part-II-2013.indd 150 ii. iii. iv. v. vi. vii. viii. ix. Maintenance of oral hygiene Caries control and restoration of decayed teeth Care of deciduous dentition Management of tooth ankylosis or locked permanent first molar Extraction of supernumerary teeth or retained deciduous tooth Maintenance of quadrant-wise tooth shedding timetable and space maintenance Management of abnormal frenal attachments and check-up for deleterious oral habits Prevention of damage to occlusion or occlusal equilibration. 12/3/2013 2:51:27 PM
  • Topic wise Solved Questions of Previous Years 151 B. Preventive procedures with use of appliances I. Mouth protectors II. Space maintenance. A. Preventive procedures without use of appliances i. Predental procedures and parental education All these preventive procedures ideally should begin before the birth of the child and are instituted before the eruption of teeth. The expecting mothers should be educated on matters like: ❍ Nutrition ❍ Proper nursing and care of the child ❍ Use of physiologic nipples ❍ Detrimental effect of prolonged use of pacifiers on dentition ❍ Correct method of brushing child’s teeth. Overall, the parents should be educated on need for maintaining good oral hygiene of the child. ii. Oral hygiene Parents and children should be taught appropriate oral hygiene measures applicable to that age group as given below: Infants (below 1 year): Brushing should start with the eruption of first primary teeth. Parents should do the gentle massage of gums and cleaning of the teeth. Toddlers (children aged between 1 and 3 years ): Toothbrush should be introduced along with some non-fluoridated pastes. Parents should do the brushing for children. Preschoolers (children aged between 3 and 6 years): Children should start brushing under parental supervision and fluoride tooth paste can be introduced. School aged (children aged between 6 and 12 years): Children should be taught proper brushing technique and regular brushing habits. iii. Caries control and restoration of decayed teeth Unrestored caries or undercontoured restoration of proximal surface of deciduous teeth lead to loss of arch length; to prevent reduction of arch length, proper restoration of affected teeth should be undertaken immediately. All possible caries prevention methods should be followed like proper tooth brushing and fluoride prophylaxis at regular intervals. iv. Care of deciduous dentition: To prevent premature loss of deciduous teeth, simple preventive measures like application of topical fluoride and pit and fissure sealants should be undertaken. v. Management of tooth ankylosis or locked permanent first molar Ankylosed deciduous teeth prevent eruption of permanent teeth or deflect them to erupt in abnormal positions; Orthodontics-Part-II-2013.indd 151 hence, they should be diagnosed and removed surgically at an appropriate time. Sometimes, permanent first molars are deeply locked by a prominent distal bulge on second deciduous molar, which prevents their eruption. It should be assessed and the slicing of distal surface of E E should be undertaken to guide the eruption of 6 6 . vi. Extraction of supernumerary teeth or retained deciduous tooth: Supernumerary teeth should be identified and extracted before they cause displacement of other teeth and interfere with normal eruption pattern and normal occlusion. vii. Maintenance of quadrant-wise tooth shedding timetable and space maintenance a. Maintenance of tooth shedding timetable is important as premature loss of deciduous teeth may cause drifting of the adjacent teeth into the space, which can result in abnormal axial inclination of teeth, spacing between teeth and shift in the midline. b. There should not be more than 3 months of gap between shedding of deciduous teeth and eruption of permanent teeth as compared to one quadrant to other quadrants. c. Space maintenance is a procedure to prevent loss of arch development due to premature loss of deciduous teeth. d. Space maintainer is an appliance or a device that prevents loss of arch length and guides the permanent teeth into correct position in dental arch. viii. Management of abnormal frenal attachments and checkup for deleterious oral habits a. The presence of abnormally thick maxillary labial fraenum produces midline diastema. A blanch test and notching of interdental bone in a periapical radiograph confirms the thick frenal attachment, which should be diagnosed and treated at an early age. b. Presence of ankyloglossia or tongue tie prevents normal functional development and results in abnormal speech and swallowing patterns. This should be treated surgically to prevent full-fledged malocclusions. c. Oral habits like finger and thumb sucking, tongue thrusting, lip biting and nail biting should be identified and stopped to enhance normal functional and deglutitional activity. d. Early correction of habits is easier and helps in elimination of the unfavourable sequelae of habits, which lead to malocclusion. ix. Prevention of damage to occlusion or occlusal equilibration a. Damage to occlusion as well as retardation of mandibular growth and possible deformities caused by orthopaedic appliances used for correction of scoliosis. Example: Milwaukee brace should be prevented by using functional appliances and positioners made of soft materials. b. All functional prematurities leading to deviation of mandibular path of closure and bruxism should be de- 12/3/2013 2:51:28 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 152 tected and selective grinding should be carried out to attain occlusal equilibration. c. Pseudo class III and crossbites caused due to functional shifts should be checked and eliminated. d. Occlusal equilibration is performed as a preventive, interceptive and corrective orthodontic procedure. Q. 2. Define preventive orthodontics and describe in brief about space maintainers and their classification with examples. Or What are the various preventive orthodontic procedures? Explain in detail about the various space maintainers. Or Describe in brief about space maintainers and their classification with examples. Or What are space maintainers? Describe the various types used in orthodontics and their indications. Ans. Graber defined preventive orthodontics as ‘the action taken to preserve the integrity of what appears to be a normal occlusion at a specific time’. Proffit and Ackerman defined it as ‘the prevention of potential interference with occlusal development. The best time to initiate preventive orthodontics is ideally during prenatal counselling’. Procedures undertaken in preventive orthodontics are as follows:A. Preventive procedures without use of appliances i. Predental procedures and parental education ii. Maintenance of oral hygiene iii. Caries control and restoration of decayed teeth iv. Care of deciduous dentition v. Management of tooth ankylosis or locked permanent first molar vi. Extraction of supernumerary teeth or retained deciduous tooth vii. Maintenance of quadrant-wise tooth shedding timetable and space maintenance viii. Management of abnormal frenal attachments and check-up for deleterious oral habits ix. Prevention of damage to occlusion or occlusal equilibration B. Preventive procedures with the use of appliances i. Mouth protectors ii. Space maintenance. Orthodontics-Part-II-2013.indd 152 Space maintainers A device used to maintain the space created by the loss of a deciduous tooth is known as space maintainer. The ideal requirements of a space maintainer are as follows: It should maintain the desired mesiodistal width or space created by premature loss of tooth. It must restore function and should be strong enough to withstand functional forces. It should not interfere with eruption of other permanent teeth. It should not exert excessive stress on adjoining teeth and should prevent supraeruption of opposing teeth. It should be simple in fabrication. It should be easily cleanable and permit good oral hygiene maintenance. CLASSIFICATION OF SPACE MAINTAINERS I. According to Hitchcock i. Removable or fixed or semi-fixed ii. With bands or without bands iii. Functional or non-functional iv. Active or passive v. Certain combinations of the above. II. According to Raymond C Thurow i. Removable ii. Complete arch a. Lingual arch b. Extraoral anchorage. iii. Individual tooth. III. According to Hinrichsen Fixed space maintainers Class I Non-functional i. Bar type ii. Loop type Removable space maintainers Example: Acrylic partial dentures Class II Example: Cantilever type (distal shoe, band and loop) Functional i. Pontic type ii. Lingual arch type Commonly used removable space maintainers Examples: i. Acrylic partial dentures 12/3/2013 2:51:28 PM
  • Topic wise Solved Questions of Previous Years 153 ❍ ii. Full or complete dentures iii. Removable distal shoe space maintainers. Removable space maintainers are mainly indicated: When there are multiple losses of deciduous teeth, which may require functional replacement and restoration of aesthetics. In case of partially erupted permanent teeth, where abutment teeth cannot support a fixed appliance. Example: ❍ Acrylic partial dentures—in cases of multiple extraction. ❍ Full or complete dentures—in cases of extraction of all primary teeth in a preschooler due to rampant caries. ❍ Removable distal shoe space maintainer—in cases of loss of deciduous second molar; shortly before eruption of first permanent molars an immediate acrylic distal shoe extension has been successfully used to guide the permanent first molar into the position. Commonly Used Fixed Space Maintainers Crown and loop: Band is replaced by a stainless steel crown. ii. Crown and loop space maintainer (Fig. 17.2) Loop Crown Fig. 17.2 Crown and loop appliance. Crown and loop space maintainers are similar to band and loop space maintainers in every aspect except that a stainless steel crown is used for abutment tooth in the place of band. It is useful where the tooth used as abutment is highly carious or pulpotomized or markedly hypoplastic. iii. Lingual arch space maintainer (Fig. 17.3) Fixed space maintainers are those that are fixed or fitted onto the teeth and require minimum or no tooth preparation. i. Band and loop space maintainer (Fig. 17.1) Stainless steel lingual arch wire D E Prematurely lost primary teeth E Loop 6 E 6 Band E 6 6 Band Fig. 17.1 Band and loop space maintainer. It is a fixed, semirigid, non-functional type of passive appliance. It is indicated for space maintenance in the posterior segments when a single tooth is lost. Example: Premature loss of deciduous canines, first molars or second molars unilaterally. Advantage: Ease of fabrication. Disadvantages: Supraeruption of opposing tooth and slipping of the loop towards gingiva. Modifications ❍ Mayne’s modification, where loop extends only on buccal side. ❍ Band and loop with vertical projection, where occlusal rest prevents tipping and sliding of the loop gingivally. Orthodontics-Part-II-2013.indd 153 Fig. 17.3 Lingual arch space maintainer. The lower lingual holding arch is a non-functional, passive, fixed appliance. It is the most effective space maintainer in cases of multiple losses of primary molars bilaterally in mandibular arch. It maintains arch perimeter by preventing both mesial drifting of the molars and lingual collapse of anterior teeth. Example: Used in cases of premature loss of deciduous first or second molars bilaterally. iv. Palatal arch appliances Palatal arch space maintainers Nance palatal holding arch Transpalatal arch 12/3/2013 2:51:28 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 154 It is primarily used in cases of premature loss of deciduous second molar prior to eruption of permanent first molars. The distal shoe appliance provides a greater control on path of eruption of unerupted permanent first molar tooth and at the same time prevents its undesirable mesial migration. vi. Aesthetic anterior space maintainer It was introduced and described by Stephen, Miller and Johnson in 1971. It is mainly used for space maintenance in premature loss of deciduous incisors. It consists of plastic teeth fixed onto a lingual arch, which in turn is attached to molar bands. Fig. 17.4 Nance holding arch. vii. Band and bar type or crown and bar space maintainer 3 E E 4 5 Fig. 17.5 Transpalatal arch. Nance holding arch (Fig. 17.4) is a maxillary palatal arch space maintainer mainly used in cases of bilateral loss of deciduous molars in maxilla. It is the appliance of choice. Transpalatal arch (Fig. 17.5) is best indicated when one side of the arch is intact and several primary teeth on other side are missing prematurely. Fig. 17.7 Band and bar space maintainer. v. Distal shoe space maintainer (intra-alveolar appliance) E 6 4 D 5 5 6 Fig. 17.8 Crown and bar space maintainer. Fig. 17.6 Distal shoe space maintainer. Distal shoe appliance (Fig. 17.6) is an intra-alveolar appliance introduced by Willets (1932) and later modified by Roche (1942). Orthodontics-Part-II-2013.indd 154 These are fixed space maintainers where abutment teeth on either side of extraction space are either banded or given stainless steel crowns and connected to each other by a bar (Figs. 17.7 and 17.8). Example: Used in cases of premature loss of deciduous first and second molars. 12/3/2013 2:51:28 PM
  • Topic wise Solved Questions of Previous Years 155 SHORT ESSAYS Q. 1. Procedures under preventive orthodontia Ans. Graber defined preventive orthodontics as ‘the action taken to preserve the integrity of what appears to be a normal occlusion at a specific time’. Proffit and Ackerman defined it as ‘the prevention of potential interference with occlusal development’. Procedures undertaken in preventive orthodontics are as follows:A. Preventive procedures without use of appliances i. Parental education ii. Caries control and restoration of decayed teeth iii. Care of deciduous dentition iv. Management of tooth ankylosis or locked permanent first molar v. Extraction of supernumerary teeth or retained deciduous tooth vi. Maintenance of quadrant-wise tooth shedding timetable and space maintenance vii. Management of abnormal frenal attachments and check-up for deleterious oral habits viii. Prevention of damage to occlusion or occlusal equilibration B. Preventive procedures with use of appliances i. Mouth protectors ii. Space maintenance. i. Parent education Ideally this should begin before the birth of the child. The expecting mothers should be educated on matters like nutrition, proper nursing and care of the child, use of physiologic nipples, ill effects of prolonged use of pacifiers on dentition and correct method of brushing the child’s teeth. Overall, the parents should be educated on need for maintaining good oral hygiene of the child. ii. Caries control and restoration of decayed teeth Unrestored caries or undercontoured restoration of proximal surface of deciduous teeth leads to loss of arch length to prevent reduction of arch length; proper restoration of affected teeth should be undertaken immediately. All possible caries prevention methods should be followed. iii. Care of deciduous dentition: To prevent premature loss of deciduous teeth, simple preventive measures like application of topical fluoride and pit and fissure sealants should be undertaken. Orthodontics-Part-II-2013.indd 155 iv. Management of tooth ankylosis or locked permanent first molar Ankylosed deciduous teeth prevent eruption of permanent teeth or deflect them to erupt at abnormal positions; hence they should be removed surgically at an appropriate time. Sometimes permanent first molars are deeply locked by a prominent distal bulge on second deciduous molar, which prevents their eruption. It should be assessed and the slicing of distal surface of E E should be undertaken to guide the eruption of 6 6 . v. Extraction of supernumerary teeth or retained deciduous tooth: Supernumerary teeth should be identified and extracted before they cause displacement of other teeth and interfere with normal eruption pattern and normal occlusion. vi. Maintenance of quadrant-wise tooth shedding timetable and space maintenance: Maintenance of tooth shedding timetable is important as premature loss of deciduous teeth may cause drifting of the adjacent teeth into the space, which can result in abnormal axial inclination of teeth, spacing between teeth and shift in the midline. Space maintenance is a procedure to prevent loss of arch development due to premature loss of deciduous teeth. vii. Management of abnormal frenal attachments and checkup for deleterious oral habits: The presence of abnormally thick maxillary labial fraenum produces midline diastema. It should be diagnosed and treated at an early age. Deleterious oral habits like finger and thumb sucking, tongue thrusting, lip biting and nail biting should be identified and stopped. Early correction of habits is easier and helps in elimination of the unfavourable sequelae of habits, which lead to malocclusion. viii. Prevention of damage to occlusion or occlusal equilibration Damage to occlusion as well as retardation of mandibular growth and possible deformities caused by orthopaedic appliances used for correction of scoliosis. Example: Milwaukee brace should be prevented. All functional prematurities leading to deviation of mandibular path of closure and bruxism should be detected and treated to attain occlusal equilibration. Occlusal equilibration is performed as preventive, interceptive and corrective orthodontic procedure. 12/3/2013 2:51:28 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 156 Q. 2. Define space maintainer. Mention its indications and contraindications. Ans. A device used to maintain the space created by the loss of a deciduous tooth is known as a space maintainer. Indications of space maintainers Space maintainers are indicated in the following conditions: Early loss of primary anterior teeth. When a second primary molar is lost before the eruption of permanent first molars and before the second premolars are ready to take its place. Early loss of the primary first molar. In cases of congenitally missing second premolars where a prosthesis is planned later. Loss of permanent first molar after eruption of second permanent molar. Active space maintainers or space regainers are used when there is minor amount of loss of space that has to be gained. Contraindications to space maintainers When there is only soft-tissue covering or very minimal amount of bone overlying the crown of erupting permanent tooth. When the space available is in excess of the mesiodistal dimension of the erupting succedaneous tooth. When the minor arch length discrepancy exists, which can be corrected with the amount of space available. Congenitally missing permanent successor. Space maintainer may not be necessary when a small period of gap exists between shedding of deciduous tooth and eruption of succedaneous tooth. Q. 3. Features of an ideal space maintainer Ans. Space maintainer is a device used to maintain the space created by the loss of a deciduous tooth. The ideal requirements of a space maintainer are as follows: It should maintain the desired mesiodistal width or space created by premature loss of tooth. It must restore function and should be strong enough to withstand functional forces. It should not get deformed, distorted or break. It should not interfere with the eruption of other permanent teeth. It should not exert excessive stress on adjoining teeth and should prevent supraeruption of opposing teeth. It should not impede the vertical eruption of adjacent tooth. It should maintain individual functional movements of the teeth. Orthodontics-Part-II-2013.indd 156 It should not interfere with normal development of occlusion. It should be able to provide mesiodistal space opening, if required. It should be simple in fabrication. It should be easily cleanable and should permit good oral hygiene maintenance. Q. 4. Preventive orthodontics Or Describe the rationale or principle of preventive orthodontic practice. Ans. Graber defined preventive orthodontics as ‘the action taken to preserve the integrity of what appears to be a normal occlusion at a specific time’. Proffit and Ackerman defined it as ‘the prevention of potential interference with occlusal development’. Preventive orthodontics is a dynamic, constant vigilance to prevent malocclusion by both the dentist and the patient or his/her parents. The rationale of preventive orthodontics is as follows: Requirements i. Establishment of a good rapport between the patient and dental surgeon: The patient should be educated about periodical check-ups in identifying the problems at an early stage and advantages of its prevention by appropriate measures. ii. Need for diagnostic records For a 2-year-old child: Clinical examination, intraoral radiographs and panoramic radiographs. For a 5-year-old child longitudinal records are required. If there are any signs of developing malocclusion, periapical radiographs should be taken once in a year. iii. Study casts Between 6 and 12 years of age study casts make up invaluable records. In required cases, study casts should be prepared every year to compare and evaluate potential problems. Identification of future orthodontic problems The critical step in preventive orthodontics is the recognition of future problem. The possible future problems can be detected by two ways: (i) clinical and (ii) radiographic indicators. i. Clinical indicators A thorough visual examination will reveal potential problems. Differentiation of potential problems from self-correcting malocclusions is essential. 12/3/2013 2:51:28 PM
  • Topic wise Solved Questions of Previous Years 157 Example: Identification of proximal caries, planning for space maintenance. ii. Radiographic indicators: Most important radiographic indicators are resorption and eruption patterns of primary and permanent dentitions, respectively. Benefits of preventive orthodontics Psychological benefits due to prevention of malocclusion. Preventive measures eliminate aetiologic factors and make it possible to restore normal growth and possibility of achieving better results. Early treatment of deleterious habits eliminates problems of malocclusion. It makes the treatment economical. SHORT NOTES Q. 1. Define preventive orthodontics. Or Enumerate preventive orthodontic procedures. Or Procedures under preventive orthodontics Ans. Graber defined preventive orthodontics as ‘the action taken to preserve the integrity of what appears to be a normal occlusion at a specific time’. Proffit and Ackerman defined it as ‘the prevention of potential interference with occlusal development’. Procedures undertaken in preventive orthodontics are as follows: i. Parental education ii. Caries control and restoration of decayed teeth iii. Care of deciduous dentition iv. Management of tooth ankylosis or locked permanent first molar v. Extraction of supernumerary teeth or retained deciduous tooth vi. Maintenance of quadrant-wise tooth shedding timetable and space maintenance vii. Management of abnormal frenal attachments and check-up for deleterious oral habits viii. Prevention of damage to occlusion or occlusal equilibration. Q. 2. Define space maintainers. Or Classification of space maintainers I. According to Hitchcock i. Removable or fixed or semifixed ii. With bands or without bands iii. Functional or non-functional iv. Active or passive v. Certain combinations of the above. II. According to Raymond C Thurow i. Removable ii. Complete arch a. Lingual arch b. Extra-oral anchorage. iii. Individual tooth III. According to Hinrichsen. Space maintainers Space maintainers Fixed space maintainers Class I Non-functional i. Bar type ii. Loop type Removable space maintainers Example: Acrylic partial dentures Class II Example: Cantilever type (distal shoe, band and loop) Functional i. Pontic type ii. Lingual arch type Classification of space maintainers Ans. Q. 3. Fixed space maintainers Definition Or Advantages of fixed space maintainers. Give an example. A device used to maintain the space created by the loss of a deciduous tooth is known as a space maintainer. Orthodontics-Part-II-2013.indd 157 12/3/2013 2:51:28 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 158 Ans. Fixed space maintainers are fixed onto the teeth either with bands or crowns. Advantages of fixed space maintainers are as follows: i. These can be used in uncooperative patients. ii. Minimum or no tooth preparation is required to fix bands and crowns. iii. Jaw growth is not affected. iv. These permit eruption of succedaneous permanent teeth and passive eruption of abutment teeth without any interference. v. If pontics are placed, masticatory function is restored. Q. 4. Oral hygiene measures during orthodontic treatment Ans. Proper oral hygiene measures throughout the orthodontic treatment are essential. Various devices and methods to maintain good oral hygiene during orthodontic treatment are as follows: i. Special orthodontic brushes wherein the middle row is shortened are used for home care. ii. Electronic tooth brushes—for patients lacking good motor control. iii. Interdental stimulation with special unitufted brushes helps to prevent soft-tissue proliferation. iv. Digital gum massage for about 5 minutes a day controls gingival proliferation. v. Waterpik is very effective in removing the debris. tooth and at the same time prevents its undesirable mesial migration. Q. 6. What are the requirements of space maintainers? Ans. Space maintainer is a device used to maintain the space created by the loss of a deciduous tooth. The ideal requirements of a space maintainer are as follows: It should maintain the desired mesiodistal width or space created by premature loss of tooth. It must restore function and should be strong enough to withstand functional forces. It should not interfere with the eruption of other permanent teeth. It should not interfere with the normal development of occlusion. It should be simple in fabrication. It should be easily cleanable and should permit good oral hygiene maintenance. Q. 7. Nance appliance Ans. i. Nance appliance (Fig. 17.9) is a type of fixed palatal arch space maintainer. Q. 5. Distal shoe space maintainer Or Willet’s appliance Ans. Distal shoe space maintainer (Fig. 17.6) is also known as eruption guidance appliance, Willet’s appliance or Roche’s appliance. Distal shoe appliance is an intra-alveolar appliance introduced by Willet’s (1932) and later modified by Roche (1942). It is primarily used in cases of premature loss of deciduous second molar prior to eruption of permanent first molars. It is of following types: i. Fixed a. Functional b. Non-functional. ii. Removable. The distal shoe appliance provides a greater control on path of eruption of unerupted permanent first molar Orthodontics-Part-II-2013.indd 158 Fig. 17.9 Nance appliance. ii. It is an appliance of choice in cases of bilateral loss of deciduous molars in maxillary arch. iii. It incorporates an acrylic button in the anterior region that contacts palatal tissue in the anterior palate without contacting the anterior maxillary teeth. iii. Advantages a. Economical b. Allows transverse growth in intercanine and permanent intermolar areas. iv. Disadvantages a. Requires good clinical skills b. Inflammation of soft tissues in anterior palatal region. 12/3/2013 2:51:28 PM
  • Topic wise Solved Questions of Previous Years 159 Topic 18 INTERCEPTIVE ORTHODONTICS LONG ESSAYS Q. 1. Define interceptive orthodontics. Enumerate the various interceptive orthodontic procedures and describe in detail about serial extraction procedure. Or, Define interceptive orthodontics. Discuss serial extraction procedure. Or Describe the indications, contraindications and technique of serial extraction. Or Define serial extraction. Discuss in detail the indications and procedure of serial extraction. Or Define serial extraction. Discuss indications and contraindications, advantages and disadvantages of serial extraction. Ans. Interceptive orthodontics has been defined as a phase of the science and art of orthodontics employed to recognize and eliminate potential irregularities and malpositions of the developing dentofacial complex. Interceptive orthodontics basically refers to measures undertaken to prevent a potential malocclusion from progressing into a more severe one. The procedures undertaken in interceptive orthodontics include the following: Serial extractions Correction of developing crossbite—anterior and posterior Control of abnormal habits Space regaining Muscle exercises Interception of skeletal malrelation Removal of soft-tissue or bony barrier to enable eruption of teeth Extraction of supernumerary and ankylosed teeth. Orthodontics-Part-II-2013.indd 159 Serial extraction Serial extraction is defined by Tweed as the planned and sequential removal of the primary and permanent teeth to intercept and reduce dental crowding problems. This procedure is usually initiated in the early mixed dentition period. It includes the planned extraction of certain deciduous teeth and later specific permanent teeth in an orderly sequence and predetermined pattern to guide the erupting permanent teeth into a more favourable position. History Kjellgren in 1929 used the term ‘serial extraction’. Nance in 1940 termed it as ‘planned and progressive extraction’ and popularized the technique in the United States. Hotz in 1970 termed it as ‘active supervision of teeth by extraction’. Rationale Serial extraction is based on mainly three principles: i. Arch length–tooth material discrepancy is corrected by reducing the tooth material. ii. Physiologic tooth movement is being utilized in serial extraction for self-correction. iii. Result of serial extraction is influenced by normal growth of dental, skeletal and soft tissues. Indications Class I malocclusion with an arch length tooth size deficiency of 10 mm or more per quadrant showing harmony between skeletal and muscular systems. As compared to tooth material, the arch length–deficiency is the most important indication for serial extraction. In patients where growth is not enough to overcome the discrepancy between tooth material and basal bone. Patients with straight profile and pleasing appearance. The arch length deficiency either unilateral or bilateral due to non-pathological causes like premature loss of canines with midline shift, malpositioned or impacted lateral incisors erupting out of the arch, bimaxillary protrusion, ectopic eruption of teeth and localized gingival recession in the lower anterior region. The arch length deficiency due to pathologic causes like extensive proximal caries and subsequent mesial migra- 12/3/2013 2:51:28 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 160 tion of buccal segment, ankylosis of tooth, premature loss of deciduous teeth, deleterious oral habits and improper proximal restorations. Contraindications Mild class I malocclusions with minimum space deficiency and skeletal class II or III malocclusion. Congenital absence of teeth—anodontia or oligodontia. Open bite and deep bite. Spaced dentition and midline diastema. Unerupted malformed teeth, e.g. dilaceration. Extensive caries or heavily filled first permanent molars. Diagnosis Study model analysis ❍ Carey’s analysis for lower arch. ❍ Arch perimeter analysis for upper arch OPG—for evaluation of eruption status of dentition ❍ Cephalometrics—assessment of skeletal tissues to study underlying skeletal relationship ❍ Clinical examination and cephalograms—for soft tissue assessment. Procedure There are three popular methods: i. Dewel’s method ii. Tweed’s method iii. Nance method. i. Dewel’s method Dewel proposed a three-step serial extraction procedure as follows: The sequence of proposed extractions: CD4 i. Step 1: Extraction of ‘C’—between 8 and 9 years to create space for alignment of incisors. ii. Step 2: Extraction of ‘D’—1 year later, i.e. at 10 years of age to accelerate eruption of first premolars. iii. Step 3: Extraction of ‘4’ (first premolar)—to permit the eruption of permanent canines in their place. The sequence of proposed extractions: D4C i. Step 1: Extraction of ‘D’ (deciduous first molars)—at 8 years of age. ii. Step 2: Extraction of ‘4’ (first premolars) and ‘C’ (deciduous canines) simultaneously. Postserial extraction therapy Most cases of serial extraction need fixed orthodontic appliance therapy for correction of axial inclination and detailing of occlusion. Advantages Treatment is more physiologic. As the treatment is carried out at an early age, psychological trauma can be avoided. It reduces duration of multibanded fixed treatment as well as retention period. Reduced risk of caries due to better oral hygiene. More stable results—as tooth material and arch length are in harmony. Disadvantages Prolong treatment time and follow-up. Regular patient visits: Cooperation of patient is needed. Tendency to develop tongue thrust due to created extraction spaces. Serial extraction requires good clinical judgement. Extraction of buccal teeth results in deepening of bite. It is not a definitive treatment; the axial inclination of teeth at the end of serial extraction procedure requires short-term fixed appliance therapy. Poorly executed serial extraction programme can be worse than none at all. Q. 2. Define interceptive orthodontics. Discuss about various procedures involved in detail. Or Modified Dewel’s technique Define interceptive orthodontics and describe various methods of interceptive orthodontics. Wherein first premolars are enucleated at the time of extraction of first deciduous molar, especially in mandibular arch where canines erupt before first premolars. Ans. ii. Tweed’s method The sequence of proposed extractions: DC4 i. Step 1: Extraction of ‘D’ (deciduous first molar)—at 8 year of age. ii. Step 2: Deciduous canines are maintained till premolars are in advanced eruptive stage. Then both ‘C’ along with first premolars ‘4’ are extracted simultaneously. iii. Nance method This method is basically modified Tweed’s method. Orthodontics-Part-II-2013.indd 160 Interceptive orthodontics has been defined as ‘the phase of science and art of orthodontics employed to recognize and eliminate potential irregularities and malpositions of the developing dentofacial complex’. Interceptive orthodontics basically refers to measures undertaken to prevent a potential malocclusion from progressing into a more severe one. The procedures undertaken in interceptive orthodontics include: i. Serial extractions ii. Correction of developing crossbite—anterior and posterior iii. Control of abnormal habits 12/3/2013 2:51:28 PM
  • Topic wise Solved Questions of Previous Years 161 iv. v. vi. vii. Space regaining Muscle exercises Interception of skeletal malrelation Removal of soft-tissue or bony barrier to enable eruption of teeth viii. Extraction of supernumerary and ankylosed teeth. i. Serial extraction Serial extraction is an interceptive orthodontic procedure that includes the planned extraction of certain deciduous teeth and later specific permanent teeth in an orderly sequence and predetermined pattern to guide the erupting permanent teeth into a more favourable position. There are three popular methods in serial extraction procedure: i. Dewel’s method ii. Tweed’s method iii. Nance method. Dewel’s method of serial extraction is the most popular method, where the sequence of proposed extractions is ‘CD4’. Extraction of deciduous canines creates the space for alignment of the incisors, whereas eruption of first premolars is accelerated by extraction of deciduous first molars. Finally, permanent first premolars are extracted to permit permanent canines to erupt into their place and achieve harmonious occlusion. ii. Correction of developing crossbite The developing crossbite should be corrected before it becomes established. The tongue blade therapy can be used to correct developing anterior crossbite in the cooperative children with adequate space for tooth in the crossbite to be moved. iii. Control of abnormal habits Habit can be defined as the tendency towards an act that has become a repeated performance, relatively fixed, consistent and easy to perform by an individual. Example: Thumb sucking, tongue thrusting, mouth breathing, etc. Due to their repetitive nature and longer duration, the deleterious orofacial habits influence the form of orofacial structures. The various modalities of treatment to control these abnormal oral habits are as follows: ❍ Elimination of cause ❍ Reminder therapy or interception of habit ❍ Corrective therapy. Interception and treatment of abnormal habits is age and severity dependent. In children aged below 3 years, no active intervention is instituted whereas children aged between 4 and 8 years need only reassurance, positive reinforcement and friendly Orthodontics-Part-II-2013.indd 161 reminders to divert the child’s attention to other things like play and toys. Screening patients for underlying psychological disturbances or any anatomical obstructions and referring to concerned professionals for appropriate treatment. Teaching correct method of swallowing to child, removal of obstruction, tongue exercises, lip exercises, etc. Use of habit-breaking appliances, both fixed and removable, are basically reminding appliances that assist to quit the habit. Some of the commonly used removable appliances include upper Hawley’s plate with tongue cribs, roller balls for tongue exercise, etc. Correction of malocclusion. iv. Space regaining Space regaining is one of the interceptive orthodontic procedures. This procedure is preferably undertaken at an early age prior to eruption of second molar. Two types of space regainers are: i. Removable space regainer ❍ Removable appliance with finger spring ❍ Removable lingual arch ❍ Expansion screws ❍ Split saddle regainer. ii. Fixed space regainers ❍ Gerber space regainer ❍ Lip bumpers ❍ Lingual arch. Commonly used space regainers are: Gerber space regainer, jack screws and cantilever spring. In case of Gerber space regainer, the forces generated by compressed coil springs bring about a distalization of first molar. In case of cantilever springs, distalization of molars can be achieved by using removable appliance incorporating simple finger springs. v. Muscle exercises The presence of normal orofacial muscle function is essential for development of normal occlusion. The aberrant muscle functions can be improved by certain muscle exercises as follows: a. Exercises for masseter muscle strengthening: The patient is asked to clench the teeth and count till 10, and then relax and repeat this over some period of time. b. Exercise for the lips and cheeks (circumoral muscles): The patient is asked to hold a piece of paper between lips, which maintains lip seal by stretching the upper lip, holding and swishing the water behind the lips, and button pull exercise, etc. c. Exercises for the tongue: One-elastic and two-elastic swallow, tongue hold exercise, etc. 12/3/2013 2:51:28 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 162 Limitations of muscle exercises are that they are not a substitute for corrective orthodontic treatment, and; if not done correctly, they can be counterproductive also. vii. Removal of soft-tissue or bony barrier: Soft tissue or any bony barrier should be removed to enable proper eruption of teeth. vi. Interception of skeletal malrelation Skeletal malrelations can be treated by taking advantage of growth potential of an individual and using myofuntional and orthopaedic appliances like headgears, chin cups, etc. viii. Extraction of supernumerary and ankylosed teeth Supernumerary teeth or any teeth that is ankylosed should be extracted so that the path of eruption of permanent teeth is not obstructed by them. SHORT ESSAYS Q. 1. Muscle exercises Ans. The presence of normal orofacial muscle function is essential for development of normal occlusion. The aberrant muscle functions can be improved by certain muscle exercises as follows: i. Exercises for masseter muscle strengthening: The patient is asked to clench the teeth and count till 10, and then relax and repeat this over some period of time. ii. Exercise for the lips and cheeks (circumoral muscles): The patient is asked to: a. Hold a piece of paper between lips which maintains lip seal by stretching the upper lip. b. Stretch the upper lip in a downward direction towards the chin. c. Holding and swishing the water behind the lips. d. Button pull exercise. e. Tug-of-war exercise with two buttons. iii. Exercises for the tongue: a. One-elastic or two-elastic swallow b. Tongue hold exercise c. Hold pull exercise. Limitations of muscle exercises are that they are not a substitute for corrective orthodontic treatment; and, if not done correctly, they can be counterproductive also. Q. 2. Interceptive orthodontics Ans. Interceptive orthodontics is defined as ‘the phase of the science and art of orthodontics employed to recognize and eliminate potential irregularities and malpositions of the developing dentofacial complex’. Interceptive orthodontics basically refers to measures undertaken to prevent a potential malocclusion from progressing into a more severe one. The procedures undertaken in interceptive orthodontics include: Orthodontics-Part-II-2013.indd 162 Serial extractions Correction of developing crossbite Control of abnormal habits Space regaining Muscle exercises Interception of skeletal malrelation Removal of soft-tissue or bony barrier to enable eruption of teeth Extraction of supernumerary and ankylosed teeth. Many of the interceptive orthodontic procedures are nothing but extension of preventive orthodontic procedures; only the difference is timing of treatment. Q. 3. Serial extractions Or Indications and contraindications for serial extraction procedures Or Indications for serial extraction Ans. Serial extraction is defined by Tweed as ‘the planned and sequential removal of the primary and permanent teeth to intercept and reduce dental crowding problems’. Indications Class I malocclusion with an arch length–tooth size deficiency of 10 mm or more per quadrant showing harmony between skeletal and muscular system. As compared to tooth material, the arch length deficiency is the most important indication for serial extraction. In patients where growth is not enough to overcome the discrepancy between tooth material and basal bone. Patients with straight profile and pleasing appearance. The arch length deficiency either unilateral or bilateral due to non-pathological causes. 12/3/2013 2:51:28 PM
  • Topic wise Solved Questions of Previous Years 163 Example: Premature loss of canines with midline shift, malpositioned or impacted lateral incisors, bimaxillary protrusion, ectopic eruption of teeth and localized gingival recession in the lower anterior region, etc. The arch length deficiency due to pathologic causes like extensive proximal caries and improper proximal restorations, ankylosis of tooth, premature loss of deciduous teeth and deleterious oral habits, etc. Contraindications Mild class I malocclusions with minimum space deficiency and skeletal class II or class III malocclusion Congenital absence of teeth—anodontia or oligodontia Open bite and deep bite Spaced dentition and midline diastema Unerupted malformed teeth, e.g. dilaceration Extensive caries or heavily filled first permanent molars. An orthodontic band or a crown is selected for tooth to be distalized. This space regainer consists of ‘U’-shaped hollow tubing soldered or welded to mesial aspect of first molar, which is to be moved distally. ‘U’-shaped rods with open coil springs of adequate length are fitted into the above tubing so that they contact mesial aspect of first molar to be moved distally. The forces generated by compressed coil springs bring about a distal movement of first molar. Space regainer using jack screws (Fig. 18.2) This appliance consists of split acrylic plate with jack screw in relation to edentulous space, and is retained using Adams clasp. Q. 4. Classify space regainers. Write briefly about any one type of space regainer. Ans. Space regaining is one of the interceptive orthodontic procedures. Space regaining procedure is preferably undertaken at an early age prior to eruption of second molar. In such patients, space lost by mesial movement of the molars can be regained by distal movement of the first molar. Commonly used space regainers are: i. Gerber space regainer ii. Jack screws iii. Cantilever spring. Gerber space regainer (Fig. 18.1) Adams clasp Jack screws Split acrylic plate Fig. 18.2 Space regainer using jack screw. Space regainer using cantilever spring (Fig. 18.3) Distalization of molar can be achieved by using removable appliance incorporating simple finger springs. Adams clasp 1st Premolar Gerber space regainer E Finger springs 1st Molar Fig. 18.1 Gerber space regainer. Orthodontics-Part-II-2013.indd 163 Fig. 18.3 Space regainer using cantilever spring. 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 164 Q. 5. Developing anterior crossbite correction. Ans. It can be treated by tongue blades, Catalans appliance, double cantilever springs. The correction of developing anterior crossbite is an interceptive orthodontic procedure. Anterior crossbites are classified as follows: Dentoalveolar Skeletal It is caused due to one or It is caused due to more maxillary teeth posi- skeletal discrepantioned in lingual relation to cies. mandibular anterior teeth. Functional (pseudo class III) It is caused due to occlusal prematurities. It can be treated by growth modification procedures using myofunctional or orthopaedic appliances. Treated by elimination of occlusal prematurities. Anterior crossbite is a condition characterized by reverse overjet. ‘The best time to treat a crossbite is the first time it is seen’. Because it is self-perpetuating and if not treated early develops into skeletal malocclusion, which requires complicated orthodontic as well as surgical procedures later for its correction. SHORT NOTES Q.1. Define serial extraction. Add a note on it. Or Define serial extraction. Or Write few indications of serial extractions. Ans. Serial extraction is defined by Tweed as ‘the planned and sequential removal of the primary and permanent teeth to intercept and reduce dental crowding problems’. Indications Class I malocclusion with an arch length tooth size discrepancy (≥10 mm). Patients with straight profile and pleasing appearance. The arch length deficiency either unilateral or bilateral due to non-pathological causes. Example: Premature loss of canines with midline shift, bimaxillary protrusion, ectopic eruption of teeth, etc. The arch length deficiency due to pathologic causes. Example: Extensive proximal caries, ankylosis of tooth and deleterious oral habits, etc. Q. 2. Muscle exercise which maintains lip seal by stretching the upper lip, holding and swishing the water behind the lips, button pull exercise, etc. Exercises for the tongue: One-elastic or two-elastic swallow, tongue hold exercise, hold pull exercise, etc. The muscle exercises are not a substitute for corrective orthodontic treatment; and, if not done correctly, they can be counterproductive also. Q. 3. Interceptive orthodontics Ans. Interceptive orthodontics is defined as ‘the phase of science and art of orthodontics employed to recognize and eliminate potential irregularities and malpositions of the developing dentofacial complex’. Interceptive orthodontics basically refers to measures undertaken to prevent a potential malocclusion from progressing into a more severe one. A few procedures undertaken in interceptive orthodontics include: serial extractions, correction of developing crossbites, control of abnormal habits, muscle exercises, etc. Many of the interceptive orthodontic procedures are nothing but extension of preventive orthodontic procedures; only the difference is timing of treatment. Ans. The aberrant muscle functions can be improved by certain muscle exercises as follows: Exercises for masseter muscle strengthening: Ask the patient to clench the teeth and count till 10 and then relax and repeat this over some period of time. Exercise for the lips and cheeks (circumoral muscles): The patient is asked to hold a piece of paper between the lips, Orthodontics-Part-II-2013.indd 164 Q. 4. Advantages of serial extraction Ans. Advantages of serial extraction are as follows: Treatment is more physiologic. As the treatment is carried out at an early age, psychological trauma can be avoided. 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 165 It reduces duration of multibanded fixed treatment as well as retention period. Reduced risk of caries due to better oral hygiene. More stable results—as tooth material and arch length are in harmony. Q. 5. Disadvantages of serial extraction Ans. Disadvantages of serial extraction are as follows: Prolong treatment time and follow-up. Cooperation of patient is needed for regular visits. Tendency to develop tongue thrust due to created extraction spaces. A good clinical judgement is required. Deepening of bite. It is not a definitive treatment, and should be followed by short-term fixed appliance therapy. Poorly executed serial extraction programme can be worse than none at all. Q. 6. Define serial extraction. Give its contraindications. Ans. Serial extraction is an interceptive orthodontic procedure that includes the planned extraction of certain deciduous teeth and later specific permanent teeth in an orderly sequence and predetermined pattern to guide the erupting permanent teeth into a more favourable position. Contraindications Mild class I malocclusions with minimum space deficiency and skeletal class II or class III malocclusion. Congenital absence of teeth—anodontia or oligodontia. Open bite and deep bite. Spaced dentition and midline diastema. Unerupted malformed teeth, e.g. dilaceration. b. Tweed’s method c. Nance method. Dewel’s method of serial extraction is the most popular method. The sequence of proposed extractions is—CD4. There are three steps: a. Extraction of ‘C’—between 8 and 9 years b. Extraction of ‘D’—at 10 years c. Extraction of ‘4’—subsequently. Extraction of deciduous canines creates the space for alignment of the incisors, whereas eruption of first premolars is accelerated by extraction of deciduous first molars. Finally, permanent first premolars are extracted to permit permanent canines to erupt into their place and achieve harmonious occlusion. Q. 8. Space regainers Ans. Space regaining is one of the interceptive orthodontic procedures. This procedure is preferably undertaken at an early age prior to eruption of second molar. Two types of space regainers are: 1. Removable space regainers a. Removable appliance with finger spring b. Removable lingual arch c. Expansion screws d. Split saddle regainer. 2. Fixed space regainers a. Gerber space regainer b. Lip bumpers c. Lingual arch. Commonly used space regainers are: Gerber space regainer, jack screws and cantilever spring. Q. 9. Developing anterior crossbite correction Q. 7. Enumerate various serial extractions procedures. Or Define serial extraction and discuss any one method of serial extraction. Ans. Serial extraction is an interceptive orthodontic procedure that includes the planned extraction of certain deciduous teeth and later specific permanent teeth in an orderly sequence and predetermined pattern to guide the erupting permanent teeth into a more favourable position. There are three popular methods in serial extraction procedure: a. Dewel’s method Orthodontics-Part-II-2013.indd 165 Or Classification of anterior crossbites Ans. The correction of developing anterior crossbite is an interceptive orthodontic procedure. Anterior crossbites are classified as follows: Dentoalveolar Skeletal Functional (pseudo class III) It is caused due to one or more It is caused due to It is caused due maxillary teeth positioned in skeletal discrep- to occlusal prematurities. lingual relation to mandibular ancies. anterior teeth 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 166 It is treated by tongue blades, It is treated by Catalans appliance, double growth modification procedures cantilever springs. using myofunctional or orthopaedic appliances. Topic 19 It is treated by elimination of occlusal prematurities. Anterior crossbite is a condition characterized by reverse overjet. ‘The best time to treat a crossbite is the first time it is seen’. Because it is self-perpetuating and if not treated early develops into skeletal malocclusion, which requires complicated orthodontic as well as surgical procedures later for its correction. METHODS OF SPACE GAINING LONG ESSAYS Q.1. Enumerate the various methods of gaining space and discuss extractions in orthodontics. Or Describe various methods to gain space in orthodontics. Give their indications and contraindications. Or What is arch length discrepancy? How will you assess the total discrepancy in a given adult patient? What methods can be used to correct arch length discrepancy? Ans. Planning space is an important aspect of the treatment planning in orthodontics. Some of the methods of gaining space include: i. Proximal stripping ii. Expansion iii. Extraction iv. Distalization v. Uprighting of molars vi. Derotation of posterior teeth vii. Proclination of anteriors. i. Proximal stripping Reproximation, slenderization, disking and proximal slicing. It is a method by which the proximal surfaces of the teeth are sliced to ↓ M–D width of the teeth. Indications When space required is minimum, i.e. 0–2.5 mm. If the Bolton’s analysis shows mild tooth material excess in either of the arches. It can be undertaken as an aid to retention in the lower anterior region. Orthodontics-Part-II-2013.indd 166 Contraindications Young patients with large pulp chamber ↑risk of pulp exposure. Patients susceptible to caries or those with high caries index. Diagnostic aids/investigations Carey’s/arch perimeter analysis (tooth material excess of 0–2.5 mm over arch length in diagnosis). Bolton analysis (reveals excess tooth material in either of arches). Diagnostic setup (helps to localize the problem and discloses amount of enamel reduction). IOPA (it gives an idea of enamel thickness and extent of pulp horns, thereby helps in estimating amount of enamel that can be removed). Procedure of proximal stripping Armamentarium Use of metallic abrasive strips Safe-sided carborundum discs Safe-sided diamond discs Very long, thin tapered fissure burs. Procedure Proximal stripping is of two types: (i) localized and (ii) generalized. Localized reduction is usually carried out in mandibular or maxillary anterior regions. In the moderate space discrepancy cases, a generalized interproximal reduction is carried out. Contact points are converted into contact areas taking care to establish proper contact between the teeth. Amount of proximal stripping Not more than 50% of enamel thickness should be reduced by proximal stripping and should be equally distributed over all teeth. 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 167 Advantages Extractions are avoided in the borderline cases where space requirement is minimal. In the patients with Bolton discrepancy a normal interarch relationship (favourable overbite and overjet relation) can be established by eliminating tooth material excess in either of the arches. More stable results can be established by broadening the contact area, which prevents slipping of contact. Disadvantages It causes roughened proximal surface that attracts plaque and calculus resulting in gingivitis. Increased caries susceptibility (proximal caries). Hypersensitivity of teeth may develop. Alteration of teeth morphology (altered aesthetics due to improper procedure/inexperienced hands). Food impaction (because of loss of normal contact between adjacent teeth). Comprehensive fluoride programme should follow this proximal stripping procedure. ii. Expansion as a method of gaining space It is a non-invasive method. Types of expansions There are three types of expansions: i. Orthodontic/dentoalveolar: Produces dental expansion with no skeletal change. ii. Passive: Results from intrinsic forces exerted by the tongue. iii. Skeletal/orthopaedic: Results from splitting of mid-palatal suture. iii. Extractions as a method of gaining space In clinical orthodontics extractions form a main part among all space gaining procedures. Extractions are indicated for correction of crowding, anteroposterior dental arch relations, vertical problems, skeletal jaw deformities and presence of supernumerary teeth. Therapeutic extractions are extractions that are undertaken as a part of orthodontic treatment. Choice of teeth for extraction depends on various factors like condition of teeth, position of teeth and position of crowding, etc. Premolars (most frequently extracted teeth) utilized for correction of anteroposterior segments. Molars or lower incisors are also preferred. iv. Distalization Moving the molars in a distal direction to gain the space is known as distalization. It has become a popular technique in recent times. Ideal timing for distalization is during mixed dentition 7 7 period prior to eruption of 7 7 . Distalization has two methods: i. Maxillary molar distalization ii. Mandibular molar distalization. Distalization Maxillary molar distalization Indications of arch expansion Crossbite (unilateral/bilateral) Constricted arches Types of expansion appliances These are broadly of two types: (i) maxillary and (ii) mandibular. Expansion appliances Maxillary Slow Removable (E.g: i. Coffin spring ii. Active plate with screws or Z springs) Orthodontics-Part-II-2013.indd 167 Fixed (E.g: i. W-arch ii. Quad helix iii. Fixed appliance with expansion screws) Mandibular (e.g. lower Schwarz plate) Rapid Banded RME (E.g: i. Haas ii. Isaacson iii. Derichsweiler Bonded RME (E.g: i. Cast metal /acrylic splints) Extraoral (e.g. headgears) Disadvantages: i. Patient cooperation is essential for timely wear of appliance. i. Appliance not worn continuously. Intermittent in action and prolonged treatment time. Mandibular molar distalization Eg: lip bumper Intraoral (removable and fixed) i. Sagittal appliance: split acrylic plate joined by jack screw. It can be used to distalize one tooth at a time. ii. Intraoral magnets: consist of repelling magnet placed on molar and a tooth anterior to it. iii. Use of open-coil springs: open-coil NiTi spring compressed between molar and anterior segment. iv. Pendulum appliance: incorporates a modified Nance button— anchorage and an SS wire with a helix, which is inserted into a sleeve on palatal aspect of molar to be distalized. v. Uprighting of molars Uprighting springs or coil springs are used. 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 168 By uprighting of mesially or distally tipped molar certain amount of space can be recovered. vi. Derotation of posterior teeth A little amount of space can be gained by correcting rotated teeth. This is best achieved by fixed appliances incorporating springs or elastics using a force couple. vii. Proclination anterior teeth Slight proclination of anterior teeth results in gaining of arch length. Indications Retroclined anteriors or cases where protracting anteriors do not affect soft-tissue profile. In patients with obtuse nasolabial angle. SHORT ESSAYS Q. 1. What are the methods of gaining space in orthodontics? Or Methods of space gaining in dental arch Ans. Various space-gaining methods are implemented in orthodontic treatment. Some of the methods of gaining space include: i. Proximal stripping ii. Expansion iii. Extraction iv. Distalization v. Uprighting of molars vi. Derotation of posterior teeth vii. Proclination of anteriors. i. Proximal stripping (reproximation, slenderization, disking and proximal slicing) It is a method by which the proximal surfaces of the teeth are sliced in order to ↓ M–D width of the teeth. It is indicated when space required is minimum, i.e. 0–2.5 mm. It is contraindicated in young patients with large pulp chambers and patients with high caries index. Not more than 50% of enamel thickness should be reduced by proximal stripping and equally distributed overall teeth. ii. Expansion as a method of gaining space It is a non-invasive method. Three types of expansions: i. Orthodontic/dentoalveolar ii. Passive expansion iii. Skeletal/orthopaedic. Arch expansion is indicated in cases with crossbite (unilateral/bilateral) and constricted arches. Types of expansion appliances: Orthodontics-Part-II-2013.indd 168 i. Maxillary, e.g. coffin spring, W-arch, quad helix, Isaacson, etc. ii. Mandibular, e.g. lower Schwarz plate. iii. Extractions as a method of gaining space In clinical orthodontics extractions form a main part among all space-gaining procedures. Extractions are indicated for correction of crowding, anteroposterior dental arch relations, vertical problems, skeletal jaw deformities and presence of supernumerary teeth, etc. Choice of teeth for extraction depends on various factors like condition of teeth, position of teeth etc. Examples: Premolars (most frequently extracted teeth) utilized for correction of anteroposterior segments. iv. Distalization Moving the molars in a distal direction to gain the space is known as distalization. It has become a popular technique in recent times. Ideal timing for distalization—during mixed dentition 7 7 period prior to eruption of 7 7 . v. Uprighting of molars Uprighting springs or coil springs are used. By uprighting of mesially or distally tipped molar, certain amount of space can be recovered. vi. Derotation of posterior teeth A little amount of space can be gained by correcting rotated teeth. This is best achieved by fixed appliances incorporating springs or elastics using a force couple. vii. Proclination anterior teeth Slight proclination of anterior teeth results in gaining of arch length. It is indicated in the cases of retroclined anteriors or cases where protracting anteriors will not affect soft-tissue profile. 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 169 Q. 2. Distal driving of molars is inserted into a sleeve on palatal aspect of molar to be distalized. Ans. Moving the molars in a distal direction to gain the space is known as distal driving or distalization of molars. It has become a popular technique in recent times. Ideal timing for distalization is during mixed dentition 7 7 period prior to eruption of 7 7 . Indications Class II cases due to maxillary prognathism. Mild to moderate protrusion/crowding in maxillary arch with normal mandible. Mild-arch discrepancy in mandibular arch. In cases of anchorage loss during orthodontic treatment. Contraindications Dental class I or class III molar relation. Bimax protrusion. Both skeletal and dental open bite cases. Cases with concave soft-tissue profile. Methods of distalization Two methods Maxillary molar distalization Extraoral (e.g. headgears) Removable (e.g. finger springs, expansion plate) Mandibular molar distalization (e.g. lip bumper) Intraoral Fixed (e.g. open-coil springs, pendulum appliance, Jones jig) Disadvantages of extraoral method Patient cooperation is essential for timely wear of appliance. Appliance not worn continuously, intermittent in action and prolonged treatment time. Intraoral method (removable and fixed appliances) Sagittal appliance A split acrylic plate joined by Jack screw can be used to distalize one tooth at a time. Intraoral magnets: consist of repelling magnet placed on molar and a tooth anterior to it. Use of open-coil springs: open-coil NiTi spring compressed between molar and anterior segments. Pendulum appliance: Incorporates a modified Nance button—anchorage and an SS wire with a helix, which Orthodontics-Part-II-2013.indd 169 Q. 3. Proximal stripping Or Slenderization Ans. Proximal stripping is also known as reproximation, slenderization, disking and proximal slicing. It is a method by which the proximal surfaces of the teeth are sliced to ↓ M–D width of the teeth. Indications When space required is minimum, i.e. 0–2.5 mm. If the Bolton analysis shows mild tooth material excess in either of the arches. It can be undertaken as an aid to retention in the lower anterior region. Contraindications Young patients with large pulp chamber ↑risk of pulp exposure. Patients susceptible to caries or those with high caries index. Diagnostic aids/investigations Carey’s/Arch perimeter analysis (tooth material excess of 0–2.5 mm over arch length in diagnosis). Bolton analysis (reveals excess tooth material in either of arches). Diagnostic setup (helps to localize the problem and discloses amount of enamel reduction). IOPA (it gives an idea of enamel thickness and extent of pulp horns; thereby helps in estimating the amount of enamel that can be removed). Procedure of proximal stripping Armamentarium Use of metallic abrasive strips Safe-sided carborundum discs Safe-sided diamond discs Very long, thin, tapered fissure burs. Procedure Proximal stripping is of two types: (i) localized and (ii) generalized. Localized reduction is usually carried out in mandibular or maxillary anterior regions. In the moderate space discrepancy cases, a generalized interproximal reduction is carried out. Contact points are converted into contact areas taking care to establish proper contact between the teeth. 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 170 Amount of proximal stripping Not more than 50% of enamel thickness should be reduced by proximal stripping and equally distributed overall teeth. Advantages Extractions are avoided in the borderline cases where space requirement is minimal. In the patients with Bolton discrepancy, a normal interarch relationship (favourable overbite and overjet relation) can be established by eliminating tooth material excess in either of the arches. More stable results can be established by broadening the contact area, which prevents slipping of contact. Disadvantages It causes roughened proximal surface that attracts plaque and calculus, resulting in gingivitis. ↑ caries susceptibility (proximal caries). Hypersensitivity of teeth may develop. Alteration of teeth morphology (altered aesthetics due to improper procedure or inexperienced hands). Food impaction (because of loss of normal contact between adjacent teeth). Comprehensive fluoride programme should follow this proximal stripping procedure. SHORT NOTES Q. 1. Molar distalization—indications Ans. Moving the molars in a distal direction to gain the space is known as distal driving or distalization of molars. It has become a popular technique in recent times. Indications Class II cases due to maxillary prognathism. Mild-to-moderate protrusion or crowding in maxillary arch with normal mandible. Mild arch discrepancy in mandibular arch. In cases of anchorage loss during orthodontic treatment. It is also used as a space-regaining procedure. To correct midline discrepancy. Q. 2. Mention few advantages of proximal stripping. Or Reproximation of teeth Or Slenderization Proximal stripping is also known as reproximation, slenderization, disking and proximal slicing. It is a method by which the proximal surfaces of the teeth are sliced to decrease M–D width of the teeth. It is indicated when space required is minimum, i.e. 0–2.5 mm. Not more than 50% of enamel thickness should be reduced by proximal stripping and is equally distributed over all teeth. Orthodontics-Part-II-2013.indd 170 Advantages Extractions are avoided in the borderline cases where space requirement is minimal. In the patients with Bolton discrepancy a normal interarch relationship (favourable overbite and overjet relation) can be established by eliminating tooth material excess in either of the arches. More stable results can be established by broadening the contact area, which prevents slipping of contact. Q. 3. What are the methods of gaining space in orthodontics? Or Enlist methods of gaining space. Ans. Various space-gaining methods are implemented in orthodontic treatment. Some of the methods of gaining space include: i. Proximal stripping ii. Expansion iii. Extraction iv. Distalization v. Uprighting of molars vi. Derotation of posterior teeth vii. Proclination of anteriors. Q. 4. Uprighting of molars Ans. 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 171 Uprighting of molars is a method gaining space in orthodontics without reducing any tooth material. Uprighting of molars is required when they are tipped either mesially or distally, occupying more space in the arch. Topic Uprighting springs or coil springs are commonly used for uprighting the molars. By uprighting of mesially or distally tipped molar certain amount of space can be recovered. 20 ARCH EXPANSION LONG ESSAYS Q. 1. Enumerate various methods to gain space in orthodontics and write in detail about rapid maxillary expansion. Or Classify expansion in orthodontics. Discuss your line of treatment for a case of 12 years with bilateral buccal crossbite. Indications of arch expansion Crossbite (unilateral/bilateral) Constricted arches. Types of expansion appliances These are broadly of two types: i. Maxillary ii. Mandibular. Expansion appliances Or Enumerate various methods to gain space in orthodontics. Discuss rapid palatine expansion. Maxillary Or Mandibular Example: lower Schwarz plate Explain rapid maxillary expansion in detail. Slow Ans. Various methods to gain the space in orthodontics include: i. Proximal stripping ii. Expansion iii. Extraction iv. Distalization v. Uprighting of molars vi. Derotation of posterior teeth vii. Proclination of anteriors. Expansion as a Method of Gaining Space Expansion is a non-invasive method of gaining the space. Removable Examples: i. Coffin spring ii. Active plate with screws or Z-springs Rapid Fixed Examples: i. W-arch ii. Quad helix iii. Fixed appliance with expansion screws Banded RME Bonded RME Examples: i. Haas ii. Isaacson iii. Derichsweiler Examples: i. Cast metal/ acrylic ii. Splints Types of expansions Rapid Maxillary Expansion (RME) There are three types of expansions: i. Orthodontic or dentoalveolar: produces dental expansion with no skeletal change. ii. Passive: results from intrinsic forces exerted by the tongue. iii. Skeletal/orthopaedic: results from splitting of mid-palatal suture. Emerson C Angell (1860) is the pioneer of rapid maxillary expansions. Nowadays, it is an important form of the orthopaedic therapy. Orthodontics-Part-II-2013.indd 171 Indications of RME Indications of rapid maxillary expansion can be considered under the following two headings: 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 172 Orthodontic indications Medical indications i. Unilateral or bilateral posterior skeletal crossbite i. Poor nasal airway ii. Narrow maxilla in certain class ii. Recurrent ear, nasal or sinus II cases infections iii. Class III malocclusion iii. Allergic rhinitis and asthma iv. Collapsed maxillary arch due to cleft palate iv. Before correction of septal deformities v. Treatment along with reversepull headgear to loosen the sutures vi. To gain space in anterior crossbite vii. High-angle cases (bonded type of RME) Principle of RME Force applied to widen the maxilla causes opening of the mid-palatal suture and induces new bone formation. The space created in the midline is initially filled with tissue fluids and blood; later, after 3–4 months, new bone fills in the space. Classification of RME appliances 1. Removable 2. Fixed a. Bonded or banded type b. Tooth-borne or tooth and tissue-borne type. 1. Removable appliances These are not effective for rapid maxillary expansion as these are not rigid enough to produce skeletal expansion. A removable appliance consists of split acrylic plate with a midline screw. Appreciable skeletal effects are produced with these appliances when treatment is performed during deciduous or early mixed dentition period. 2. Fixed rapid maxillary expansion appliances Different types of banded RMEs: The difference in appliance design of various banded RME appliances is based on various types of screws and mode of attachment. They are as follows: i. HAAS type In this type of banded RME a heavy stainless steel wire (0.045 inch or 1.15 mm) is welded and soldered along the palatal aspects of the band. The free ends are turned back to be embedded in acrylic. The screw used in this type of RME is similar to Derichsweiller type. ii. Isaacson type It is a tooth-born appliance without any palatal acrylic covering. The drawback of expansion screw is the build-up of pressure, which is hazardous to the tissue. A special spring-loaded screw called a ‘MINNE’ expander is used in this design soldered directly to the bands to overcome the pressure build up and to make the force application smooth and constant. iii. Hyrax or Biedermann type Biedermann type RME uses Hyrax (hygienic rapid expander) screw. Hyrax screws have heavy gauge wire extensions, which are adapted to the palatal contour, welded and soldered to the palatal aspect of the bands on premolars and molars. iv. Derichsweiller type In this type of appliance the screw is connected to the bands by means of wire tags that are welded and soldered to the palatal aspect of band on one side and embedded in acrylic on the palatal aspects of all non-banded teeth except the incisors. Acrylic adapts to the palate and is in two halves to permit activation of screw. b. Bonded RME appliance In bonded RME, instead of bands, metallic cap splints or acrylic covering is used. These can be bonded or banded or tooth borne, tooth and tissue borne. i. Cast metal cap splints: Cast cap splints to which screws are soldered are prepared for all the teeth and the entire assembly is cemented or bonded. a. Banded RME appliances In these usually the first premolars or deciduous molars and first permanent molars are banded. These are joined labially and palatally by soldering with heavier gauge wire. The basic RME appliance is the screw, which is placed in the midline. ii. Acrylic splints Thick gauge stainless steel wire is closely adapted buccally and palatally around the posterior teeth from premolars to molars, and a screw is soldered to the wire. Acrylic is covered over the occlusal, buccal and palatal occlusal-third of all the posterior teeth and the assembly is cemented or bonded. Orthodontics-Part-II-2013.indd 172 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 173 Advantages of bonded RME Bonded appliances are useful in high-angle cases. The occlusal acrylic covering acts as a splint and prevents the increase in mandibular angle. Appliance management in children below 15 years of age Activated twice a day. 90° activation each time, with a total of 180° activation per day. 0.5 mm per day. Review after 1 week. Pain is felt in patients who are in late adolescence and adults due to build up of force. Slight discomfort may be felt during expansion. Persistent pain is noticed in patients whose suture is fused. In such cases, activation should be stopped. SARPE( surgically assisted rapid palatal expansion) In adults, palatal osteotomies lateral to mid-palatal suture is done to assist rapid expansion. Clinical implications of expansion Mid-palatal suture does not open evenly, but opens in a ‘V’ fashion with the broad end of the ‘V’ in anterior region and apex at the posterior region. Occlusal and frontal cephalometric radiographs will reveal the suture opening. Force recorded during rapid expansion is in the range of 10 –20 lb. Usual treatment period is 2 weeks and the relapse is higher after RME; hence overcorrection is advised. Tissue changes observed with RME Tissue changes can be observed in bone, sutures and dental structures. Bone changes Maxilla moves laterally due to expansion and also rotates with the fulcrum at frontonasal suture. Downward and backward rotation of the mandible with increase in mandibular angle. Increase in nasal airway, reduction in airway resistance. Sutural changes Space created by sutural opening is filled with tissue fluid and haemorrhage; and later the area is invaded by osteoblasts. New bone is deposited at the edges of palatal process and the space is gradually filled with the bone. Dental changes Initially teeth move labially by translation and later there is an increased buccal inclination of the posterior teeth with slight extrusion. Appearance of median diastema, which later closes due to the pull of trans-septal fibres. Tissue reaction after expansion At the end of active expansion, 80% skeletal and 20% dental expansion occurs. After 4 months, 50% skeletal and 50% dental changes are observed. Relapse is highest during the first 6 weeks after expansion; there is more skeletal relapse while dental correction is retained. Retention schedule after RME The objective of retention is to hold the expansion while the forces generated have decayed. The same fixed RME appliance is used as retainer for first 3 months, with the hole of the screw filled with self-cure acrylic. From the fourth month onwards removable retainers are given and are worn full time for about 9 months after expansion; and later, half time wear is advised. SHORT ESSAYS Q. 1. Arch expansion Ans. Arch expansion is a non-invasive method of gaining the space. Types of expansions: There are three types of expansions. i. Orthodontic or dentoalveolar expansion: produces dental expansion with no skeletal change. Orthodontics-Part-II-2013.indd 173 ii. Passive expansion: results from intrinsic forces exerted by the tongue. iii. Skeletal or orthopaedic expansion: results from splitting of mid-palatal suture. Indications of arch expansion i. Crossbite (unilateral/bilateral) ii. Constricted arches. Types of expansion appliances: These are broadly of two types: (i) maxillary and (ii) mandibular. 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 174 Expansion appliances Q. 3. Indications of rapid maxillary expansion Or Maxillary Slow Removable Examples: i. Coffin spring ii. Active plate with screws or Z-springs Mandibular Example: lower Schwarz plate Rapid Fixed Examples: i. W-arch ii. Quad helix iii. Fixed appliance with expansion screws Banded RME Bonded RME Examples: i. Haas ii. Isaacson iii. Derichsweiler Examples: i. Cast metal/ acrylic ii. Splints Q. 2. Expansion screws Ans. A typical expansion screw consists of an oblong body divided into two halves, with each half consisting of threaded inner side that receives one end of a doubleended screw. The screw has a central basing with four holes, which receive a key used to turn the screw. The turning of screw to 90° brings about linear movement of 0.18 mm. Various types of expansion screws used in removable and fixed appliances are: Jack screws, coffin springs, quad helix, Isacson, Hyrax and Derischweiler, etc. Activation schedule: To achieve desired results, different activation schedules have been advocated by different authors. The most popular ones are: i. Schedule by Timms ii. Schedule by Zimring and Isaacson. According to Timms: ❍ In patients up to 15 years old: 90° rotation in the morning and evening. ❍ In patients over 15 years old: 45° activation 4 times a day. According to Zimring and Isaacson: ❍ In growing individuals: Two turns each day for 4–5 days and later one turn per day till the desired expansion is achieved. ❍ In non-growing adults: Two turns each day for first 2 days and later one turn per day for next 5–7 days and one turn every alternate day till the desired expansion is achieved. Orthodontics-Part-II-2013.indd 174 Rapid palatine expansion Ans. The rapid maxillary expansion is also called as rapid palatal expansion. It is a skeletal type of expansion that involves separation of mid-palatal suture and movement of the maxillary shelves away from each other. Emerson C Angell (1860) is the pioneer of rapid maxillary expansions. Nowadays, it is an important form of the orthopaedic therapy. Indications of RME: Indications of rapid maxillary expansion can be considered under following two headings: Orthodontic indications Medical indications i. Unilateral or bilateral posterior skeletal crossbite i. Poor nasal airway ii. Narrow maxilla in certain class ii. Recurrent ear, nasal or sinus II cases infections iii. Class III malocclusion iii. Allergic rhinitis and asthma iv. Collapsed maxillary arch due to cleft palate iv. Before correction of septal deformities v. Treatment along with reversepull headgear to loosen the sutures vi. To gain space in anterior crossbite vii. High-angle cases (bonded type of RME) Types of appliances used for rapid maxillary expansion are as follows: i. Removable appliances ii. Fixed appliances a. Tooth bone, e.g. Isacson type and Hyrax type b. Tooth and tissue born, e.g. Derischweiler type and Hass type. Q. 4. Compare rapid and slow palatal expansions. Or Dental versus skeletal expansion Ans. The comparable features between rapid and slow palatal expansion are as follows: 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 175 Features Rapid expansion Any age iii. Rate of expansion Rapid Slow iv. Indication Skeletal crossbite cases in class II and III Cases of minor space discrepancy vi. Type of tissue reaction Traumatic Physiologic Mostly fixed appliance Either fixed or removable More frequent 0.5–1 mm/day Less frequent 1 mm/month ix. Duration of treatment Short duration about 2–3 weeks Long duration around 2–3 months x. Retention Before fusion of mid-palatal suture (young growing individuals) ii. Age Milder forces around 2–4 pounds viii. Frequency of activation i. Nature of expan- Mostly skeletal and Mainly dental sion even dental v. Force level used Greater forces around 10–20 lb vii. Type of appliance used Slow expansion 9 months 3 months SHORT NOTES Q. 1. Slow-expansion appliance Q. 3. Coffins spring Ans. Ans. Slow expansion is traditionally known as dentoalveolar expansion, although some minute skeletal changes can also be seen. Expansion is done slowly at the rate of 0.5–1 mm/week. The forces generated by slow expansion are much less, around 2–4 lb. As compared to rapid expansion the slow expansion produces more stable results and less relapse. Coffins spring is a slow-expansion appliance introduced by Walter Coffin. RME Design The spring is made up of a 1.25 mm heavy stainless steel wire. It consists of a ‘U’ or omega-shaped loop positioned in the mid-palatal region. The distal ends of the U-loop are limited to the distal of first permanent molar. It is a continuous type of spring where both ends are fixed to the base plate. The appliance is activated by expanding the appliance manually by pulling the sides apart—first in the anterior region and then in the posterior region. An expansion of 2–3 mm is made during activation. Ans. Indications Q. 2. Rapid maxillary expansion Or The rapid maxillary expansion is also called as rapid palatal expansion and is a skeletal type of expansion. Emerson C Angell (1860) is the pioneer of rapid maxillary expansions. Nowadays, it is an important form of the orthopaedic therapy. It is indicated in the cases of unilateral or bilateral posterior skeletal crossbite, narrow maxilla in certain class II and III cases of malocclusion, and collapsed maxillary arch due to cleft palate. It is also indicated in certain medical conditions like poor nasal airway, allergic rhinitis and asthma. Recurrent ear, nasal or sinus infections. Both removable and fixed types of appliances used for rapid maxillary expansion. Examples: Isacson type, Hyrax type, Derischweiler type and Hass type. Orthodontics-Part-II-2013.indd 175 Expansion of constricted maxillary arch and correction of crossbite. Conditions requiring differential expansion. Advantages Economical. Differential expansion of arch is possible. Less bulky. Disadvantage It is unstable, if not made precisely. Q. 4. Expansion screws Or Expansion devices 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 176 Ans. A typical expansion screw consists of an oblong body divided into two halves, with each half consisting of threaded inner side that receives one end of a doubleended screw. The screw has a central basing with four holes, which receive a key used to turn the screw. Various types of expansion screws used in removable and fixed appliances are: Jack screws, Coffin springs, quad helix, Isacson, Hyrax and Derichsweiler, etc. To achieve desired results, different activation schedules have been advocated by different authors. The most popular ones are scheduled by Timms and Zimring and Isaacson. Q. 5. Role of expansion as a method of gaining space Ans. Expansion has a unique place among various methods to gain the space in orthodontics like proximal stripping, extractions, distalization and uprighting of molars, proclination of anteriors. Types of expansions: There are three types of expansions as follows: i. Orthodontic or dentoalveolar expansion: Produces dental expansion with no skeletal change ii. Passive expansion: Results from intrinsic forces exerted by the tongue. iii. Skeletal or orthopaedic expansion: results from splitting of mid-palatal suture. Arch expansion is indicated in crossbite (unilateral/bilateral) cases and constricted arches. There are broadly of two types of expansion appliances: (i) maxillary and (ii) mandibular. Q. 6. Give indications for rapid palatine expansion. Ans. Indications of rapid maxillary expansion can be considered as follows: Orthodontic indications Medical indications i. Unilateral or bilateral posterior i. Poor nasal airway skeletal crossbite ii. Narrow maxilla in certain class ii. Recurrent ear, nasal or sinus II cases infections iii. Class III malocclusion iii. Allergic rhinitis and asthma iv. Collapsed maxillary arch due to cleft palate iv. Before correction of septal deformities Orthodontics-Part-II-2013.indd 176 v. Treatment along with reversepull headgear to loosen the sutures vi. To gain space in anterior crossbite vii. High-angle cases (bonded type of RME) Q. 7. Derichsweiler appliance Ans. Derichsweiler type of appliance is a type of banded RME appliance. In this type of appliance, the screw is connected to the bands by means of wire tags that are welded and soldered to the palatal aspect of bands on first premolars and first molars on one side and embedded in acrylic on the palatal aspects of all non-banded teeth except the incisors. Acrylic adapts to the palate and is in two halves to permit activation of screw. Q. 8. Hyrax screw Ans. Hyrax screw is a type of screw used in fixed rapid maxillary banded RME expansion appliance. Hyrax or Biedermann type of RME uses Hyrax (hygienic rapid expander) screw. Hyrax screws have heavy gauge wire extensions, which are adapted to the palatal contour, and welded and soldered to the palatal aspect of the bands on premolars and molars. Q. 9. Quad helix appliance Ans. Quad helix is one of the appliances used to expand a narrow maxilla. The quad helix incorporates four helices that increase the wire length; therefore the flexibility and range of action of this appliance is more. The appliance is constructed using a 0.038 inch wire and is soldered to bands on the first molars. The quad helix can be used to expand a narrow arch as well as to bring about rotation of molars and a slow dentoalveolar expansion. It can be preactivated by stretching the two molar bands apart prior to cementation or by using three prong pliers after cementation. When it is used in children during deciduous and early mixed dentition periods, a skeletal mid-palatal splitting can be achieved. 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 177 Topic 21 EXTRACTIONS LONG ESSAYS Q. 1. Describe in detail about extractions in orthodontics. Or What are the reasons for extractions in orthodontics? Discuss the choice of teeth for extractions. Or How will you plan extractions in orthodontic treatment? Or Classify extractions in orthodontics. Write about therapeutic extractions in detail. Ans. In clinical orthodontics, extractions form a main part among all space-gaining procedures. Calvin S Case was the pioneer of extraction philosophy in orthodontics, which was later supported by Charles Tweed. Reasons for extraction Extractions are indicated for correction of crowding, anteroposterior dental arch relations, vertical problems, skeletal jaw deformities and presence of supernumerary teeth, etc. as described below. i. Correction of crowding Crowding usually results from arch length and tooth material discrepancy; hence prior to extraction a careful analysis of tooth size–arch length discrepancy should be performed. In many cases the tooth material–arch length disproportion cannot be treated by ↑ the arch length. Hence, ↓ of tooth material is the only alternative. In case of severe tooth material–arch length discrepancy extraction of one or more teeth is undertaken to correct the malocclusion. ii. Correction of sagittal interarch relationship The cases of abnormal sagittal malrelationships like class II or class III malocclusion may require extraction of teeth to achieve normal sagittal interarch relationships. In Angle’s class I cases: It is preferable to carry out extractions in both arches. Orthodontics-Part-II-2013.indd 177 In Angle’s class II: In most class II cases, it is possible to reduce the abnormal maxillary proclination by extracting only first premolars in the upper arch. In Angle’s class III: It is beneficial to avoid extraction in upper arch. These are preferably treated by extraction only in the lower arch or by extraction in both arches. iii. Abnormal size and form of teeth Deformed teeth, which interfere with normal occlusion, necessitate their extraction to achieve satisfactory occlusion. Examples: Macrodontia, severe hypoplastic teeth, dilacerations and abnormal crown morphology. iv. Skeletal jaw malrelations: Respective surgical procedures along with extractions may be required in the correction of severe skeletal malrelationship of the jaws that may not be satisfactorily treated using orthodontic appliances alone. v. Preservation of symmetry: Extractions may be undertaken to correct any asymmetry in dental arches. Choice of teeth for extraction or indications for extraction Choice of teeth for extraction depends on various factors like condition of teeth, position of teeth and position of crowding, etc. Teeth Indications for extraction i. Maxillary incisors (rarely extracted) i. Grossly carious and unrestorable incisors. ii. Unfavourably impacted or totally blocked buccally or lingually. iii. In cases where one lateral is congenitally missing, the other may be extracted to maintain arch symmetry. iv. Malformations of incisor crowns or teeth with dilacerated root. v. Trauma or irreparable damage to incisors by fracture. ii. Mandibular incisors i. Totally locked buccally or lingually. ii. Severe trauma, gingival recession or bone loss. iii. Severe arch length deficiency with fanning of lower anteriors. iv. For correction of lower incisor crowding in mild class II cases. iii. Canines i. Ectopically erupted or unfavourably impacted. (seldom ii. Totally blocked buccally or lingually. extracted) iii. Deciduous canine extracted as part of serial extraction. iv. Premature shedding of a deciduous canine usually indicates the extraction of its fellow on the opposite side of the arch to restore symmetry. 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 178 v. In class II cases, if the lower deciduous canines are shed early; the upper deciduous canines should also be removed to avoid worsening of the postnormalcy (class II tendency). vi. In class III cases, if the upper deciduous canines are shed early, it may necessitate the extraction of lower deciduous canines to avoid worsening of prenormalcy (class III tendency). iv. First premolars (teeth of choice for extraction) i. To relieve moderate-to-severe crowding U/L arch and proclination, in class II division I or class I bidental protrusion. Reasons for the extraction of first premolars are: • Their location in the arch is such that the space gained by their extraction can be utilized for correction both in the anterior as well as posterior region. • The contact that results between the canine and second premolar is satisfactory. v. Second premolars i. To relieve mild discrepancy of crowding and proclination. ii. Unfavourably impacted. iii. In open bite cases. iv. If grossly decayed or have a questionable prognosis. vi. First molars i. To correct mild crowding or proclination. ii. Grossly decayed with poor prognosis. iii. In open bites cases to encourage deepening of the bite. viii. Second i. To prevent third molar impaction. molars ii. To enable distalization of first molar. viii. Third molars No extraction for orthodontic purposes. Various extraction techniques are as follows: i. Wilkinson’s extractions ii. Balancing extractions iii. Compensating extractions iv. Serial extractions v. Extractions in camouflage treatment vi. Driftodontics. i. Wilkinson’s extraction technique Wilkinson advocated extraction of all 6 6 between the 66 age of 8½ and 9½ years. Basis for this extraction is of the fact that the first permanent molars in children are highly susceptible to caries. Advantages Impaction of third molars can be avoided by making the space available for their eruption. In general, crowding of arch is minimized, thereby lowering the risk of caries. Orthodontics-Part-II-2013.indd 178 Extraction technique makes it possible to maintain oral hygiene effectively. Drawbacks The extraction of first molars offers limited space for alleviation of crowding. The second bicuspids and second molars rotate and may tip into the extraction space. Deprivation of adequate anchorage for any orthodontic tooth movement. Improper contacts lead to accumulation of plaque and calculus, resulting in periodontal problems. ii. Balancing extractions Removal of teeth symmetrically on either side of the arch is known as balanced extraction. Removal of teeth on one side of the arch results in asymmetry; to prevent these extractions have to be balanced to allow equal movement of remaining teeth towards extraction site on both the sides of the arch. iii. Compensating extractions Extraction of teeth in opposing jaws or arches is known as compensating extractions. This type of extractions preserve interarch relationship and maintain lateral symmetry. iv. Serial extractions Robert Bunon introduced the concept of serial extraction. The name ‘serial extraction’ was coined by Kjellgren. Extraction of certain deciduous and permanent teeth in a sequence to alleviate crowding is known as serial extraction. Usual sequence of extraction is first primary canines followed by primary first molars and then permanent first premolars (C, D, 4). v. Driftodontics or extractions of permanent teeth without appliance therapy Extraction of the lower first premolars 44 is often asso- ciated with spontaneous decrowding of lower anteriors. It is referred to as driftodontics and is less frequent in the upper arch. These may be the instances when the extraction of a permanent tooth is not followed by orthodontic treatment for varied reasons such as non-availability of specialist or point unsuitable for fixed appliance therapy. These types of extractions are preferable. 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 179 SHORT ESSAYS Q. 1. Describe the factors that justify extraction of teeth for treating malocclusion. Ans. The factors that justify the extraction of teeth for treatment of malocclusion are as follows: In clinical orthodontics extractions form a main part among all space-gaining procedures. Extractions are indicated for: i. Correction of crowding: Crowding usually results from arch length and tooth material discrepancy. In case of severe tooth material–arch length discrepancy extraction of one or more teeth is undertaken to correct the malocclusion. ii. Correction of sagittal interarch relationship: The cases of abnormal sagittal malrelationships like class II or class III malocclusion may require extraction of teeth either in one arch or both the arches to achieve normal sagittal interarch relation. iii. Abnormal size and form of teeth: Deformed teeth that interfere with normal occlusion necessitate their extraction to achieve satisfactory occlusion. Examples: Macrodontia, dilacerations and abnormal crown morphology. iv. Skeletal malrelations of jaws: In the correction of severe skeletal malrelationship of the jaws, respective surgical procedures along with extractions may be required. v. Preservation of symmetry: Extractions may be undertaken to correct any asymmetry in dental arches. Q. 2. Wilkinson’s extractions Ans. Wilkinson advocated extraction of all first permanent molars 6 6 between the age of 8½ and 9½ years, which is 66 known as Wilkinson’s extraction technique. Basis for this extraction is the fact that the first permanent molars in children are highly susceptible to caries. Advantages Impaction of third molars can be avoided by making the space available for their eruption. In general, crowding of the arch is minimized, thereby lowering the risk of caries. Extraction makes it possible to maintain oral hygiene effectively. Orthodontics-Part-II-2013.indd 179 Drawbacks The extraction of first molars offers limited space for alleviation of crowding. The second bicuspids and second molars rotate and may tip into the extraction space. Deprivation of adequate anchorage for any orthodontic tooth movement. Improper contacts lead to accumulation of plaque and calculus, resulting in periodontal problems. Q. 3. Serial extractions Ans. Robert Bunon introduced the concept of serial extraction. The name ‘serial extraction’ was coined by Kjellgren. Extraction of certain deciduous and permanent teeth in a sequence to alleviate crowding is known as serial extraction. Three popular methods of serial extraction are as follows: i. Dewel’s method ii. Tweed’s method iii. Nance method. i. Dewel’s method: Dewel proposed a three-step serial extraction procedure. The sequence of proposed extractions is CD4. Step 1: Extraction of ‘C’—between 8 and 9 years to create space for alignment of incisors. Step 2: Extraction of ‘D’—one year later, i.e. at 10 years of age to accelerate eruption of first premolars. Step 3: Extraction of ‘4’ (first premolar)—to permit the eruption of permanent canines in their place. Modified Dewel’s technique: In this technique first premolars are enucleated at the time of extraction of first deciduous molar, especially in the mandibular arch where canines erupt before first premolars. ii. Tweed’s method The sequence of proposed extractions—DC4 Step 1: Extraction of ‘D’ (deciduous first molar)—at 8 years of age. Step 2: Deciduous canines are maintained till premolars are in advanced eruptive stage. Then both ‘C’ (deciduous canines) along with first premolars ‘4’ are extracted simultaneously. 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 180 iii. Nance method: This method is basically modified Tweed’s method. Step 2: Extraction of ‘4’ (first premolars) and ‘C’ (deciduous canines) simultaneously. The sequence of proposed extractions—D4C Postserial extraction therapy Step 1: Extraction of ‘D’ (deciduous first molars) — at 8 years of age. Most cases of serial extraction need fixed orthodontic appliance therapy for correction of axial inclination and detailing of occlusion. SHORT NOTES Q. 1. Extraction in orthodontics Ans. In clinical orthodontics extractions form a main part among all space-gaining procedures. Extractions are indicated for correction of crowding, anteroposterior dental arch relations, vertical problems, skeletal jaw deformities and presence of supernumerary teeth. Therapeutic extractions are extractions that are undertaken as a part of orthodontic treatment. Choice of teeth for extraction depends on various factors like condition of teeth, position of teeth and position of crowding, etc. Premolars (most frequently extracted teeth) utilized for correction of anterior and posterior segments. Molars or lower incisors are also preferred. Q. 2. Therapeutic extraction in orthodontics Ans. When teeth are extracted for orthodontic correction, it is called therapeutic extraction. In orthodontics, extractions are indicated for correction of crowding, anteroposterior dental arch relations, vertical problems, skeletal jaw deformities and presence of supernumerary teeth, etc. as per the need of the situation. Q. 3. Wilkinson’s extraction Ans. Wilkinson advocated extraction of all first permanent molars 6 6 between the age of 8½ and 9½ years, which is 66 known as Wilkinson’s extraction technique. Basis for this extraction is the fact that the first permanent molars in children are highly susceptible to caries. By this technique of extraction, impaction of third molars can be avoided; crowding of arch is minimized, thereby lowering the risk of caries and maintaining good oral hygiene. Orthodontics-Part-II-2013.indd 180 The drawbacks of this extraction technique are that the adjacent teeth rotate and may tip into the extraction space; deprivation of adequate anchorage for any orthodontic tooth movement and improper contacts lead to accumulation of plaque and calculus, resulting in periodontal problems. Q. 4. Planning extractions Ans. In clinical orthodontics extractions form a main part among all space-gaining procedures. Calvin S Case was the pioneer of extraction philosophy in orthodontics, which was later supported by Charles Tweed. In planning extractions, ‘think organized’, i.e. malocclusion should be analysed first in the anteroposterior, then vertical and finally in transverse plane. Extractions are indicated for correction of crowding, anteroposterior dental arch relations, vertical problems, skeletal jaw deformities and presence of supernumerary teeth, etc. as the situation exists. Extractions should not be done if they affect soft-tissue balance. Q. 5. Impacted tooth and its orthodontic correction Or Impacted canines Ans. Teeth are impacted due to a variety of reasons like arch length discrepancy, abnormal developmental position, deflection in the path of eruption, etc. The possible methods of treatment for an impacted tooth are: i. Leave as it is ii. Extraction iii. Surgical exposure only iv. Surgical exposure and orthodontic alignment. If the impacted tooth or canine is asymptomatic and wellaligned, it can be left as it is with periodic follow-up. 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 181 If the teeth is unfavourably positioned, or shows signs of pathology or causes resorption of adjacent teeth then it should be extracted. If the impacted tooth is favourably positioned with unobstructed path of eruption and is well within the eruptive period then only surgical exposure is enough. Topic 22 If impacted tooth is malpositioned, having insufficient space available in arch on eruption or associated with orthodontic problems, then it should be exposed surgically and mechanical approaches should be used, e.g. nitinol wires, auxiliary arrangement springs like PG springs, magnets, etc. should be utilized to align the tooth in the arch. ORTHODONTIC APPLIANCES: GENERAL PRINCIPLES LONG ESSAYS Q. 1. What are the advantages and disadvantages of removable and fixed appliances? Or What are the indications and contraindications of removable and fixed orthodontic appliances? Or Define orthodontic appliances. Classify them. State the advantages of fixed and removable appliances. Or Compare the merits and demerits of removable and fixed orthodontic appliance. Ans. Orthodontic appliances are devices by which mild pressure may be applied to a tooth or a group of teeth and their supporting structures to bring about necessary changes within the bone, which will allow the tooth movement. Orthodontic appliances are broadly classified into two groups: 1. Mechanical appliances a. Removable b. Fixed. 2. Myofunctional appliances a. Removable b. Fixed. Mechanical appliances: These exert mild pressure on a tooth or a group of teeth and their supporting structures in a predetermined direction with the help of active components like springs, elastics, screws, etc., which are part of the appliance itself. Myofunctional appliances: These are loose-fitting or passive appliances that harness the natural forces of the orofacial Orthodontics-Part-II-2013.indd 181 musculature, which are transmitted to the teeth and alveolar bone through the medium of the appliance. These either transmit, or eliminate or guide the natural perioral muscle forces onto the dentition. These do not contain active components and are used for growth modification procedures. Removable appliances Advantages Disadvantages i. Ability to maintain oral hygiene. i. Patient cooperation is needed. ii. Usually, used for simple ii. Inability to perform complex tooth movements that can be tooth movements. brought about by tipping. iii. Less chair side time of orthodontist to fabricate them so they can handle more number of patients. iii. The treatment duration is prolonged in case of severe malocclusion, as whenever multiple tooth movements are to be carried out it should be done one at a time. iv. Simple movements like tip- iv. Complex tooth movements ping, overbite reduction can like multiple rotations are difficult to treat using removable be undertaken. appliances. v. Lesser forces are used. So v. It is very difficult to close the strain on anchor teeth is residual space by forward lesser than fixed. movement of posterior teeth in cases of extraction. vi. These can be used by gen- vi. There is a great chance of eral dental practitioners who patient misplacing or damhave received basic training. aging the removable appliances. vii. Relatively is economical vii. These cannot be used in compared to fixed appliances. severe cases of class II and III malocclusions with unfavourable growth pattern. viii. Damaged appliances that apply undesirable forces can be removed by the patient. 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 182 Fixed appliances Advantages iii. Aesthetic requirements iv. Hygienic requirements. Disadvantages i. Fixed appliances offer bet- i. Oral hygiene maintenance is ter control and to a large extent more difficult. lessen the need for patient cooperation. ii. It is easy to bring about various ii. These take up more chairside types of tooth movements, e.g. time as these are time consuming tipping, bodily movement, rota- to fix and adjust. tion, intrusion and extrusion. iii. As multiple tooth movements are possible simultaneously, the treatment duration is considerably reduced. iii. Aesthetically unpleasing, unless modern tooth-coloured appliances or lingual orthodontics are used. iv. More precise tooth movements iv. These require special training and correction of occlusion is of the operator and are invariably possible using fixed appliances. handled by specialized orthodontists. v. Fixed appliances are used to v. Damaged appliances that apply treat most malocclusions, includ- misdirected forces cannot be reing very complicated ones. moved by the patient. vi. These appliances offer better vi. More expensive. control over anchorage. Q. 2. What are the basic requirements of an orthodontic appliance? Ans. Ideal requirements of an orthodontic appliance are categorized under the following headings: i. Biologic requirements ii. Mechanical requirements i. Biologic requirements The appliance should bring about desired tooth movements. The appliance should not interfere with normal growth and function. The appliance should not produce pathologic changes such as root resorption, periodontal damage or nonvitality of the teeth. The appliance should not bring about sudden and unwanted tooth movements. The materials used in fabrication should be biocompatible and should not produce toxic effects. ii. Mechanical requirements The appliance should be: i. Simple to fabricate. ii. Strong enough to withstand masticatory forces. iii. Able to deliver controlled force of desired intensity, duration and direction. iv. Universally applicable, i.e. must be able to handle various malocclusions. The appliance should not be bulky and should be comfortable to the patient in using it. iii. Hygienic requirement The appliance should be self-cleansing, or easy to clean or should not interfere with oral hygiene maintenance. iv. Aesthetic requirements The appliance should be aesthetically acceptable and should be inconspicuous as possible. SHORT ESSAYS Q. 1. Compare fixed and removable appliances Ans. Fixed appliances Removable appliances i. Fixed appliances offer better control and to a large extent lessen the i. Patient cooperation is needed to a large extent. need for patient cooperation. ii. Oral hygiene maintenance is more difficult. ii. Oral hygiene maintenance is easy. iii. As multiple tooth movements are possible simultaneously, the treat- iii. The treatment duration is prolonged in case of severe malocclusion ment duration is considerably reduced. as whenever multiple tooth movements are to be carried out it should be done one at a time. iv. These take up more chairside time as these are time consuming to iv. Less chairside time of orthodontist to fabricate them so these can fix and adjust them. handle more number of patients. v. More expensive. v. Relatively economical compared to fixed appliances. vi. These require special training of the operator and are invariably han- vi. These require no special training and can be used by general dental dled by specialized orthodontists. practitioners who have received basic training. Orthodontics-Part-II-2013.indd 182 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 183 SHORT NOTES Q. 1. Mention three ideal requisites of an orthodontic appliance. Ans. Ideal requirements of an orthodontic appliance are as follows: i. The appliance should bring about only desired tooth movements. Topic 23 ii. It should not interfere with normal growth and function. iii. It should be simple to fabricate but strong enough to withstand masticatory forces. iv. It should not be bulky and should be comfortable to the patient in using it. v. It should be self-cleansing or easy to clean. vi. It should be aesthetically acceptable. REMOVABLE ORTHODONTIC APPLIANCES LONG ESSAYS Q. 1. Discuss the advantages, disadvantages and indications for using removable orthodontic appliance. Ans. The advantages and disadvantages of removable orthodontic appliances are as follows: Advantages Disadvantages i. Ability to maintain oral i. The need for patient cooperation hygiene ii. Usually used for simple ii. Inability to perform complex tooth tooth movements that can movements be brought about by tipping iii. Less chair side time of orthodontist to fabricate them so they can handle more number of patients iii. In case of severe malocclusions the treatment duration is prolonged, as whenever multiple tooth movements are to be carried out it should be done one at a time iv. Various movements like iv. It is difficult to treat multiple rotatipping, overbite reduction tions using removable appliances can be undertaken v. Lesser forces are used. So v. In cases requiring extraction, it is the strain on anchor teeth is very difficult to close residual space by lesser than fixed forward movement of posterior teeth vi. General dental practi- vi. The chances of patient misplacing tioners who have received or damaging the removable appliances adequate training can use are more them vii. Less inventory is re- vii. Patients should have enough skill quired for fabrication to remove and replace the appliance without distorting them Orthodontics-Part-II-2013.indd 183 viii. Relatively more eco- viii. Severe cases of class II and III nomical than fixed appli- malocclusions with unfavourable ances growth pattern cannot be treated using removable appliances ix. As they take less chair ix. These require more regular moniside time and are more toring economical, they can be used in community-based programmes wherein large number of patients are treated x. These are less conspicuous and aesthetically more pleasing when compared to fixed appliance xi. The patient can remove damaged appliances that apply undesirable forces by himself Various types of malocclusions that can be treated by removable mechanical appliances are as follows: i. Mild and moderate proclination ii. Anterior and posterior crossbite iii. Median diastema iv. Generalized anterior spacing v. Buccally placed canines and premolars vi. Palatally placed canines vii. Deep overbite viii. Anterior open bite. 12/3/2013 2:51:29 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 184 Q. 2. Define and classify orthodontic appliances. Discuss how the various types of tooth movement are achieved using removable appliances. Or Discuss the treatment of different types of malocclusion with removable appliances. Ans. Orthodontic appliances are defined as devices by means of which mild pressure may be applied to a tooth or a group of teeth and their supporting structures so as to bring about necessary changes within the bone which will allow the tooth movement. Orthodontic appliances are broadly classified into two groups: 1. Mechanical appliances a. Removable b. Fixed. 2. Myofunctional appliances a. Removable b. Fixed. Mechanical appliances They exert mild pressure on a tooth or a group of teeth and their supporting structures in a predetermined direction with the help of active components, which are part of the appliance itself. The treatment of different types of malocclusions by removable mechanical appliances are as follows: i. Mild proclination Hawley’s appliance Hawley’s appliance with long labial bow if there is space distal to canine. ii. Moderate proclination Roberts’ retractor iii. Median diastema Upper Hawley’s appliance with two-finger springs to move both the central incisors mesially towards each other Upper plate with split-type labial bow Simple Hawley’s appliance if the median diastema is due to proclination. iv. Generalized anterior spacing High labial bow with apron spring Hawley’s appliance with the base plate trimmed on the palatal aspect. v. Anterior crossbite Hawley’s appliance with posterior bite plane and ‘Z’spring to correct the tooth in crossbite Upper anterior expansion (Schwarz appliance) with posterior bite plane Orthodontics-Part-II-2013.indd 184 Inclined plane if the bite is deep. vi. Posterior crossbite Schwarz-type lateral expansion with posterior bite plane for occlusal clearance Hawley’s appliance with posterior bite plane and ‘T’springs or ‘Z’-springs to correct the tooth in crossbite vii. Buccally placed canine Buccal canine retractor when palatal and distal movement is required Helical loop canine retractor when the sulcus depth is shallow viii. Buccally placed premolar Spring for palatal movement of premolars. ix. Palatally placed canine Hawley’s appliance with ‘Z’-spring and posterior bite plane when only buccal movement is required Palatal canine retractor with posterior bite plane when both distal and buccal movement of canine is required. x. Deep over bite Upper Hawley’s appliance with flat anterior bite plane. xi. Anterior open bite In cases of open bite caused due to habits, upper Hawley’s appliance with tongue spikes is advised and posterior bite planes to intrude molar. Q. 3. Enumerate ideal properties of an orthodontic appliance and describe various types of canine retractors. Ans. Ideal requirements of an orthodontic appliances are categorized as follows: a. Biologic requirements The appliance should bring about only desired tooth movements without any sudden and unwanted tooth movements. The appliance should not interfere with normal growth and function. The appliance should not produce pathologic changes such as root resorption, periodontal damage or non-vitality of the teeth. The material used in fabrication should be biocompatible and should not produce toxic effects. b. Mechanical requirements The appliance should be simple to fabricate and strong enough to withstand masticatory forces. It should be able to deliver controlled force of desired intensity, duration and direction. The appliance should not be bulky and should be comfortable to the patient. 12/3/2013 2:51:29 PM
  • Topic wise Solved Questions of Previous Years 185 c. Hygienic requirement Appliance should be self-cleansing, or easy to clean or should not interfere with oral hygiene maintenance. d. Aesthetic requirements Appliance should be aesthetically acceptable. With more number of adults seeking orthodontic treatment, the appliance should be acceptable aesthetically. It should be less visible. e. Cost factor Appliance should be economical for the patient. It should not be expensive. CANINE RETRACTORS Canine retractors are springs that are used for distal movement of canines. The canine retractors can be classified as follows: 1. Based on location a. Buccal—buccally placed b. Palatal—palatally placed. 2. Based on presence of helix or loop a. Canine retractor with helix b. Canine retractor with loop. 3. Based on the mode of action a. Push type b. Pull type. 4. Based on placement position a. Buccally placed i. Buccal canine retractor ii. Helical-loop canine retractor iii. U-loop canine retractor. b. Palatally placed i. Palatal canine retractor. 1. Buccal canine retractor Indications It is indicated in cases of buccally placed canines and canines placed high in the vestibule. They are used where a buccally placed canine has to be moved both palatally and distally. Spring design It is made up of 0.7 mm or 21 gauge SS wire. It consists of a coil of 3 mm diameter, an active arm and a retentive arm. Coil is placed as high as possible in between the present and future positions of canine, i.e. distal to long axis of canine. The end of the spring is bent at right angle to the canine to be moved and then shaped to the tooth. Tag should cross over the mesial side of second premolar. Modifications There are two modifications of buccal canine retractor: Orthodontics-Part-II-2013.indd 185 a. Supported or sleeved b. Self-supported or stabilized. The supported canine retractors are made of thinner gauge wire (0.5 mm). Thus, they are more flexible and therefore mechanically efficient. As they lack the stability, they are enclosed in a stainless steel tubing. The self-supported canine retractors are made of thicker gauge wire (0.7 mm) so that the spring can support itself. Activation of buccal canine retractor It is one of the few springs where the coil is closed for activation. The self-supported canine retractors are activated by closing the helix 1 mm at a time, while the supported canine retractors can be activated up to 2 mm at a time. Activation is done by using ‘hollow chop’ pliers like Mathews or Andresen’s. 2. Reverse-loop canine retractor or helical-loop canine retractor Indications It is indicated in patients with shallow sulcus and especially in the mandibular arch. Spring design It is made up of 0.7 mm or 21 guage SS wire. It consists of a helix or coil of 3 mm diameter, an active arm and a retentive arm. The mesial arm or retentive arm is adapted between the premolars. The distal arm is active and bent at right angles to engage the canine below the height of contour. The coil is placed 3–4 mm below the gingival margin. The height of the coil can be adjusted based on the vestibular height. Drawbacks It is stiff in the horizontal plane and unstable vertically. Activation There are two methods of activation. It is activated either by opening the helix by 1 mm or by cutting 1 mm of the free end and readapting it around the canine. 3. ‘U’-loop canine retractor It is made up of 0.7 mm or 21 gauge SS wire. Indications Mechanically, it is least effective and indicated when minimal distal retraction of 1–2 mm of canine is required. Spring design It consists of a ‘U’ loop, an active arm and a retentive arm, which is distal. The base of the ‘U’ loop should be 2–3 mm below the cervical margin. The mesial arm of the ‘U’ loop is bent at right angles and adapted around the canine below its mesial contact point. 12/3/2013 2:51:30 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 186 Advantages Ease in fabrication, simple in design and less bulky. Disadvantage This is the least efficient of all the canine retractors. Activation It is activated by closing the loops by 1–2 mm, or cutting the free end of the active arm by 2 mm and readapting it. 4. Palatal canine retractors which are part of the appliance itself. The active components may include springs, elastics, screws, etc. Myofunctional appliances: They are loose-fitting or passive appliances that harness the natural forces of the orofacial musculature, which are transmitted to the teeth and alveolar bone through the medium of the appliance. They either transmit, eliminate or guide the natural perioral muscle forces onto the dentition. They do not contain active components and are mainly used for growth modification procedures. This is similar to finger springs and is made up of 0.6 mm stainless steel wire. COMPONENTS OF REMOVABLE ORTHODONTIC APPLIANCE Indication There are three basic components in a removable orthodontic appliance: 1. Retentive components 2. Active components 3. Base plate. 1. Fixation or retention components a. Clasps b. Bows 2. Active components a. Springs b. Labial bows c. Screws d. Elastics. 3. Anchorage a. Clasps b. Contact of base plate with non-moving part c. Headgears d. Intermaxillary elastics. 4. Base plate forms the framework. It is indicated in retraction or distalization of palatally placed canines. Spring design It consists of an active arm, a guide arm or retentive tag, and a coil of 3 mm diameter. The active arm is placed mesial to canine. The helix or coil is placed along the long axis of the canine and as far away as possible to have retractor a good range of action. Retentive tag gets embedded in the acrylic plate. Activation It is done by either of the following: Opening the coil/helix by 2–3 mm at a time. Pulling the free arm of the spring slightly away from the point of emergence from coil. Tension can be given to the spring by squeezing the coil with the tip of the pliers. Q. 4. Classify orthodontic appliances and name the basic components of a removable appliance. Or Classify orthodontic appliances and explain the retentive components of removable orthodontic appliances and Adams clasp in detail. Ans. CLASSIFICATION OF ORTHODONTIC APPLIANCES Broadly two groups Mechanical appliances Myofunctional appliances i. Removable ii. Fixed Mechanical appliances: Exert mild pressure on a tooth or a group of teeth and their supporting structures in a predetermined direction with the help of active components, Orthodontics-Part-II-2013.indd 186 RETENTIVE COMPONENTS The retentive components help in keeping the appliance in place and resist displacement of the appliance. The success of a removable appliance is to a large extent dependent upon good retention of the appliance. The wire components that aid in retention of a removable appliance are called clasps. Mode of action of clasps: They act by engaging the undercuts of the teeth. The various clasps can be classified under two broad headings: 1. Free-ended clasps in which one end of the clasp is embedded in acrylic. For example: ❍ C-clasp ❍ Triangular clasp ❍ Ball end clasp ❍ Duyzing clasp ❍ Crozat clasp ❍ Arrow pin clasp 12/3/2013 2:51:30 PM
  • Topic wise Solved Questions of Previous Years 187 ❍ Wrought Roach clasp ❍ Visick’s clasp ❍ Lingual extension clasps. 2. Continuous clasp in which both ends of the clasp are embedded in acrylic. 2. Jackson’s clasp (Fig. 23.2) Requirements of an ideal clasp Offer adequate retention Offer adequate retention even in the presence of shallow undercuts It should 3. South end clasp (Fig. 23.3) This clasp is used when retention in anterior region is required. Fig. 23.3 South end clasp. 4. Triangular clasp (Fig. 23.4) i. It is used between two adjacent posterior teeth. ii. Indicated when additional retention is needed. Fig. 23.4 Triangular clasp. 5. Ball end i. Preformed wires with ball at one end are available. clasp Or (Fig. 23.5) Ball can be made at the end of the wire with silver solder. ii. Indicated when additional retention is required. Permit usage in both fully-erupted and partial erupted teeth Fig. 23.5 Ball end clasp. Be easy to fabricate By itself apply any active force that would bring about undesirable tooth movements of an old age tooth It should not Impinge on soft tissues 6. Schwarz clasp (Fig. 23.6) Interfere with normal occlusion CLASPS 1. Circumferential clasp (Fig. 23.1) Fig. 23.2 Jackson’s clasp. ii. It engages all undercuts, i.e. buccal, cervical, mesial and distal. iii. Wire is adapted along the buccocervical margin and both the proximal undercuts, then carried over the occlusal embrasures to end as retentive arms on both sides of the molar. iv. Advantage: It is simple to construct and offers adequate retention. v. Disadvantage: It offers inadequate retention in partially erupted teeth. For example: ❍ Jackson’s clasp ❍ Arrowhead clasp ❍ Eyelet clasp ❍ Adams clasp ❍ Delta clasp ❍ South end clasp. Types of clasps based on the undercuts used: 1. Clasps using mesial/distal undercuts ❍ Adams clasp ❍ Triangular clasp ❍ Ball end clasps ❍ Arrowhead/Schwarz clasp ❍ Crozat clasp. 2. Using buccal/lingual undercuts ❍ Jackson’s clasp ❍ South end clasp ❍ Duyzing’s clasp. 3. Using both the proximal and buccal lingual undercuts ‘C’-clasp. i. It is also called full clasp or ‘U’ clasp. Predecessor of Adams clasp: Number of arrowheads engage interproximal undercuts between molars and premolars. Drawbacks i. Special pliers are required. ii. Difficult and time consuming to fabricate. iii. Large amount of space in buccal vestibule. iv. Injures interdental soft tissue. i. It is also known as three-quarter clasp or ‘C’clasp. Fig. 23.6 Schwarz clasp. Fig. 23.1 ‘C’-clasp. ii. It is a simple clasp designed to engage the buccocervical undercut. iii. Advantage: Simplicity of design and fabrication. iv. Disadvantage: It cannot be used in partially erupted teeth wherein the cervical undercut is not available for clasp fabrication. Orthodontics-Part-II-2013.indd 187 7. Crozat It resembles full clasp with additional piece of clasp (Fig. soldered wire which engages mesial and distal 23.7) undercuts. Fig. 23.7 Crozat clasp. 8. Adams clasp i. It is also known as Liverpool clasp, universal clasp or modified arrowhead clasp. 12/3/2013 2:51:30 PM
  • Quick Review Series for BDS 4th Year: Orthodontics 188 ADAMS CLASP It is described by Professor Philip Adams. It is also known as Liverpool clasp, universal clasp and modified arrowhead clasp. It is constructed using 0.7 mm round SS wire. Parts of Adams clasp are: ❍ Two arrowheads—(i) engage mesial and (ii) distal undercuts; ❍ Bridge—connects to arrowheads and is at 45° to long axis of tooth; and ❍ Two retentive arms. Advantages It is rigid and offers excellent retention. It can be fabricated on both deciduous and permanent teeth. It can be used on partially or fully erupted teeth. It can be used on molars, premolars and incisors. No specialized instrument is needed to fabricate the clasp. It is small and occupies minimum space. The clasp can be modified in a number of ways. Modifications of Adams clasp are as follows: i. Adams clasp with single arrowhead ii. Adams clasp with ‘J’-hook iii. Adams clasp with incorporated helix iv. Adams clasp with additional buccal tube v. Adams clasp with soldered buccal tube vi. Adams clasp with distal extention. Adams clasp on incisors and premolars. i. Adams clasp with single arrowhead (Fig. 23.8). A helix can be incorporated in the bridge of the Adams clasp to help in engaging elastics. iv. Adams clasp with additional arrowhead (Fig. 23.11). Fig. 23.11 Adams clasp with additional arrowhead. This additional arrowhead engages the proximal undercut of adjacent tooth and is soldered onto the bridge of the Adams clasp. This type of clasp offers additional retention. v. Adams clasp with soldered buccal tube (Fig. 23.12). Fig. 23.12 Adams clasp with soldered buccal tube. Buccal tube soldered to bridge of the Adams clasp. It permits the use of extraoral anchorage using face bow head area assembly. vi. Adams clasp with distal extension (Fig. 23.13). Fig. 23.13 Adams clasp with distal extension. Distal arrowhead of Adams clasp has a small extension incorporated distally, which helps in engaging elastics. vii. Adams clasp on incisors and premolars (Fig. 23.14). Fig. 23.14 Adams clasp on incisors and premolars. Fig. 23.8 Adams clasp with single arrowhead. Usually indicated in partially erupted tooth. In last erupted molar single arrowhead is made to engage the mesioproximal undercut of tooth. Bridge is modified to encircle the tooth distally and ends on palatal aspect as a retentive arm. ii. Adams clasp with ‘J’-hook (Fig. 23.9). Adams clasp can be fabricated in the incisors and PMs when retention in those areas is required. These may span over single tooth or two teeth. Q. 5. What are the various active components of removable orthodontic appliances? Write about springs. Ans. Fig. 23.9 Adams clasp with ‘J’-hook. ‘J’-hook can be soldered onto bridge of the Adams clasp, which is useful in engaging elastics. iii. Adams clasp with incorporated helix (Fig. 23.10). Fig. 23.10 Adams clasp with incorporated helix. Orthodontics-Part-II-2013.indd 188 The active components of removable orthodontic appliances are: 1. Bows 2. Screws 3. Elastics 4. Springs. 1. Bows Bows are active components of removable orthodontic appliances, which are mostly used for incisor retraction. 12/3/2013 2:51:30 PM
  • Topic wise Solved Questions of Previous Years 189 There are various types of bows routinely used in orthodontics, e.g., short labial bow, long labial bow, split labial bow, reverse labial bow, Robert’s retractor, Mill’s retractor, etc. 2. Screws Screws are active components that can be incorporated in a removable appliance. The removable appliances that make use of screws can bring about three types of tooth movements: a. Arch expansion. b. Movement of a group of teeth in a buccal or labial direction. c. Movement of one or more teeth in a distal or mesial direction. 3. Elastics Elastics as active components are rarely used along with removable appliances. Removable appliances using elastics for anterior retraction generally make use of a labial bow with hooks placed distal to the canines. 4. Springs Springs are active components of removable appliances. There are various methods of classification of springs. SPRINGS Classification of Springs 1. Based on their ability to withstand forces of distortion a. Self-supported springs i. Buccal canine retractor ii. U-loop canine retractor iii. Helical-loop canine retractor iv. Coffin springs. b. Guided springs i. Cantilever springs ii. Finger springs iii. Palatal canine retractor iv. ‘T’-springs. c. Auxiliary springs i. Apron springs. 2. Based on their point of attachment a. Free-ended springs i. Cantilever springs ii. Finger springs iii. Canine retractors iv. ‘T’-springs. b. Springs attached at both ends i. Labial bows ii. Coffin springs. c. Accessory springs attached to arches i. Apron springs. Orthodontics-Part-II-2013.indd 189 3. Based on presence of loops or helix i. Helical springs ii. Looped springs. The detail description of some commonly used springs is as follows: A. Self-supported springs The springs that can resist on their own the distortion forces are known as self-supported springs. These are made of 0.7 mm or 0.9 mm hard SS wire. These usually have a stability ratio of 1. The various springs that fall under the category of selfsupported springs are: 1. Canine retractors a. Buccal canine retractor b. Helical-loop canine retractor c. ‘U’-loop canine retractor. 2. Coffin springs. 1. Canine retractors a. Buccal canine retractor It is indicated in cases of buccally placed canines and canines placed high in the vestibule. It made up of 0.7 mm or 21 gauge SS wire. It consists of a coil of 3 mm diameter, an active arm and a retentive arm. It is one of the few springs where the coil is closed for activation. Activation is done by using ‘hollowchop’ pliers like Mathews or Andresen’s. b. Helical loop canine retractor or reverse loop canine retractor It is indicated in patients with shallow sulcus and especially in the mandibular arch. It is made up of 0.7 mm or 21 gauge SS wire. It consists of a helix or coil of 3 mm diameter, an active arm and a retentive arm. The coil is placed 3–4 mm below the gingival margin. The height of the coil can be adjusted based on the vestibular height. It is stiff in the horizontal plane and unstable vertically. It is activated either by opening the helix by 1 mm, or by cutting 1 mm of the free end and readapting it around the canine. c. ‘U‘-loop canine retractor It is made up of 0.7 mm or 21 gauge SS wire. It consists of a ‘U’-loop, an active arm and a retentive arm, which is distal. The base of the ‘U’-loop should be 2–3 mm below the cervical ma