Orthodontic assessment


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Orthodontic assessment

  1. 1. Guy’s, King’s and St Thomas’ Schools of Medicine, Dentistry and Biomedical Sciences GKT Dental Institute University of London BDS GKT Programme Year 4 & 5 2003 / 2004 Orthodontics Course organisers: Professor F McDonald Student Name N.B. A charge of £6 will be levied for replacement of these notes
  2. 2. LIST OF CONTENTS OUTLINE OF THE ORTHODONTI DEPARTMENT COURSE 3 Aims & Objectives of the Undergraduate Orthodontic Course 3 Year 4 3 Year 5 3 GDC REGULATIONS FOR ORTHODONTICS 4 ORTHODONTIC COURSE TIMETABLE 5 Year 4 Spring & Summer 5 Year 5 Summer, Autumn & Spring 5 Internal assessment for Year 5 5 LECTURE LIST (Year 4 and 5) 6 ORTHODONTIC UNDERGRADUATE TEACING TIMETABLE AT GUY’S CAMPUS 7 TEXT BOOKS 7 THE ORTHODONTIC DIAGNOSTIC FORM 8 Initial Details 8 1. Reason for Attendance 8 2. Past Medical History 8 3. Family History 8 4. Past Dental History 9 5. Skeletal Patterns 9 6. Soft Tissue Patterns 9 7. Oral Examination 10 8. Report of Radiographs 12 9. Attitude of Parents 12 10. Conclusions 12 1
  3. 3. INFORMATION HANDOUTS AVAILABLE IN THE DEPARTMENT TO GIVE TO PATIENTS Handout 1 - A Guide to Orthodontic Treatment 14 CEPHALOMETRIC RADIOGRAPHY 16 Basic Cephalometric Analysis 17 Cephalometric Landmarks 21 REVISION NOTES Appendix Pages Classification of Occlusion and Malocclusion 1 Development of Dentition and Occlusion 2 Aetiology of Malocclusion: Skeletal and Soft Tissue Factors 3 Aetiology of Malocclusions: Local Factors 5 Orthodontic Diagnosis and Treatment Planning 8 Class I Malocclusions 10 Class II Division 1 Malocclusions 12 Class II Division 2 Malocclusions 14 Class III Malocclusions 16 Removable Appliances 17 Fixed and Functional Appliances 19 Facial Growth and Orthodontics 20 Tooth Movement and Retention 22 2
  4. 4. Aims of course To provide a comprehensive course giving the undergraduate student a sound foundation in orthodontic diagnosis and treatment planning to enable the qualified student to recognise a developing malocclusion and be confident to deal with it or refer for appropriate specialist treatment at the correct time. Year 4 Each student attends once a fortnight for a clinical teaching session consisting of a tutorial and clinical exercises and a clinical patient session. All patients are seen by the whole group each session and students work in groups of 2 or 3 to carry out diagnosis and treatment planning for patients and appropriate appliance demonstration treatment patients are seen. At the end of the year 4, students should know the basics of aetiology, diagnosis and treatment planning for all malocclusions, and the use and adjustment of specific removable appliances. Requirements for year 4 are:- a) attendance at clinical sessions and participation in diagnosis and treatment planning. b) able to take impressions, insert, adjust and be familiar with specific removable appliance designs. c) obtain pass mark in year 4 written exam. Year 5 Students attend clinical teaching sessions consisting of a tutorial (for which the topic and essay plans have been prepared and reading material is given in advance of each tutorial and full participation is expected) and clinical exercises and a clinical patient session. The clinical patient session will be new patients for diagnosis and treatment planning. Again all patients are seen by the whole group each session and students work in groups of 3 to carryout diagnosis and treatment planning. In addition, during the spring term students should also observe and become familiar with contemporary treatment techniques by observing postgraduate patients undergoing specific fixed appliance treatments under consultant supervision. At the end of year 5, students should have a comprehensive knowledge of aetiology, diagnosis and treatment planning and be aware of the possible range of modern orthodontic techniques available and specifically know what and when to refer for specialist advice and treatment. Requirements for year 5 are:- a) attendance at clinical sessions and participation in diagnosis and treatment planning. b) participation in tutorials for prepared topics. c) observation of fixed appliance techniques, bonding, placement and adjustment of archwires, retainer placement and adjustment, making safe broken appliances. d) obtain pass mark in year 5 written exam and clinical viva. 3
  5. 5. At the completion of the course each student should have fulfilled the current GDC regulations (‘The First Five Years’, second edition 2002) :- 1). ORTHODONTICS a) be competent at carrying out an orthodontic assessment including an indication of treatment need b) be competent at managing appropriately all forms of orthodontic emergency including referral when necessary. c) be competent at making appropriate referrals based on assessment d) have the knowledge to be able to explain and discuss treatments with patients and their parents e) have the knowledge to be able to design, insert and adjust space maintainers f) have the knowledge to design, insert and adjust active removable appliances to move a single tooth or correct a crossbite g) be familiar with contemporary treatment techniques h) be familiar with the limitations of orthodontic treatment 2). ORTHODONTICS Orthodontics is concerned with the development and growth of the face and occlusion the extent of normal variation in the form and function of both the hard and soft tissues of the mouth and face, and particularly the ways in which such variation produces differences in occlusion. The study of these factors should emphasise their inter-relationship with the general and psychosocial development of the individual. Changing patterns of orthodontic care have been influenced by changes in the perception of simple orthodontic treatment by both patients and practitioners. Most orthodontic treatment is now delivered by specialists. Students should be able to:- a) Carry out orthodontic assessment. b) Identify treatment needs. c) Understand the role of orthodontics in overall patient care. d) Recognise and describe developing and manifest malocclusions. e) Understand the appropriate timing of interventions and what these interventions are likely to be. f) See and assist in the delivery of all forms of orthodontic treatment. g) Make safe all forms of orthodontic appliances. h) Know when and how to refer for specialist advice. i) Recognise and manage those problems of the mixed dentition where interceptive treatment is indicated, including space maintenance. 4
  6. 6. Orthodontic Course Timetable Year 4. Clinical timetable. Students attend once a fortnight for a clinical teaching session. Spring term clinical teaching sessions 1) Clinical diagnosis. 2) Radiographic assessment – use of radiographs – lateral ceph. 3) Treatment planning and appliance design exercises. 4 & 5) Treatment planning exercise with models and radiographs for class I. (Crowding and spacing) 6 & 7) Treatment planning exercise with models and radiographs for class II div. 1 and class II div. 2. Summer term clinical teaching sessions 8 & 9) Treatment planning exercise with models and radiographs for class III and crossbite. Internal assessment for year 4. (50% of total internal orthodontic assessment)(10% BDS) 1 hour short question answer paper at end of summer term. Year 5. Summer term clinical teaching sessions. 10) Treatment planning exercises with models and radiographs for anterior open bite. 11) Extra oral traction. – Clinical aspects, theory and uses. 12) Functional appliances. – Clinical aspects theory and uses. Autumn term clinical teaching sessions. 13) Soft tissues. 14) The unerupted maxillary canine. 15) Fixed versus removable appliances. 16) Referral to specialist and I O T N. 17) Timing of treatment, interceptive, adult. 18) Tooth movement, retention and stability. 19) Revision. Spring term 1). Clinical competency diagnostic exam and 2) retake exam if required. (3 sessions attachments to postgraduates) Internal assessment for year 5. (50% of total internal orthodontic assessment)(5% +5% of BDS). 1). 1¼ hours (2 out of 3 essay questions) written exam in December. 2). Clinical competency diagnostic exam. 10 minute viva following a 20 minute examination of a patient with appropriate x-rays in January/February. Lecture list 5
  7. 7. Year 4 (Spring and summer term) Introduction to orthodontics, classification of malocclusion Prof. McDonald. Introduction to removable appliance design Dr. Derringer. Treatment planning: choice of extractions and appliance therapy Dr. Derringer. Development of dentition Dr. Derringer. Aetiology of malocclusion – skeletal and soft tissues, habits Dr. Hill. Aetiology of malocclusion – local and dental factors Miss Padhani. Class I malocclusion Prof. McDonald. Class II div. 1 malocclusion Miss Padhani. Class II div. 2 malocclusion Miss Padhani. Class III malocclusion Prof. McDonald. Crossbites Dr. Derringer. Functional appliances Dr. Derringer. Anchorage and extra-oral traction Dr. Hill. Facial growth and timing of treatment Prof. McDonald. Histology of tooth movement, stability and retention Dr. Hill Referral to specialist and IOTN Miss Padhani. Year 5 Cleft lip and palate – topic teaching with OS 6
  8. 8. Orthodontic undergraduate teaching at Guy’s campus:- Monday Tuesday Wednesday Thursday Friday am Year 4 / 5 Year 4 Year 4 / 5 Year 5 Year 4 / 5 Miss Padhani Mr Thom Dr. Derringer Dr. Derringer Mrs Dowsett pm Year 4 / 5 Year 4 Year 4 / 5 Year 5 Year 4 / 5 Mrs Dowsett Miss Gibilaro Dr. Hill Mrs Dowsett Dr. Derringer Text Books F.McD & A.J.I = Diagnosis of the Orthodontic Patient (1998) (Available from Floor 22, Guy’s campus Tower). W.H.O.N. = Walther and Houston's Orthodontic Notes (5th edition) HS&T = Textbook of Orthodontics, Houston, Stephens and Tulley (2nd edition) C.D.S. = Companion to Dental Studies, Volume 3, Clinical Dentistry L.M. = An Introduction to Orthodontics, Laura Mitchell (1996) 7
  9. 9. THE ORTHODONTIC DIAGNOSTIC FORM Introduction (A copy of the form is shown above). This sheet will be used by students with patients presenting for orthodontic diagnosis. The completed form will be discussed at a Teaching Clinic when the assessment is modified as necessary. Although the information as detailed is retained for record purposes, the main purpose of the form is as an aid to learning and teaching, thus students should not hesitate to complete the details to the best of their ability. Any important medical history is normally revealed prior to orthodontic consideration but this is checked and confirmed during this investigation. The following notes indicate the order in which the various points are determined and recorded in each section of the chart. Initial Details These are generally self-evident - Clinic Name and date of Teaching Clinic on which patient is presented. Referred by - The TYPE of practice from which the patient has been referred e.g. G.D.P. - General Dental Practitioner, C.D.S - Community Dental Service or another department in the hospital. 1. Reason for Attendance This is to establish whether the patient and parents know why they have been referred and whether they have engineered the consultation of their own initiative. Replies help in assessing likely co- operation. 2. Past Medical History The medical history should be taken as for all patients seeking general dental treatment with the special aim of establishing any unusual medical history that may provide - a - Contra-indication to prolonged treatment b - Possible difficulties associated with extractions c - High risk patients e.g. Hepatitis B and HIV positive patients 3. Family History a) Note any similar dental irregularities (e.g. diastema) or familial skeletal discrepancy (e.g. Class III tendency). b) History of prior orthodontic treatment for other members of family - will help to assess co-operation. c) Observe if parent(s) possess own teeth or dentures. 4. Past Dental History 8
  10. 10. i. Any information on previous extractions and methods of anaesthesia. Patients rarely give you a clear history of how many teeth have been extracted and when. ii Traumatic incidents to the mouth should be recorded with dates eg. fractured incisors. iii Determine the frequency of previous dental inspections. iv Note nature and length of any previous orthodontic treatment. Habits Note the presence of digit-sucking habits or dates at which such habit ceased (often if stated to be relatively recent, habit may in fact be continuing, though intermittently). For the avid thumb- sucker, determine how many hours a day the digit is in the mouth. 4. Skeletal Patterns Clinical Assessment of the External Facial Appearance a) Antero-posterior Note should be made of the sagittal relationship of the tooth bearing areas of the mandible and maxilla. The 'A' and 'B' points are assessed clinically and any obvious discrepancy noted using the shorthand Skeletal I, II or III. b) Vertical A most important aspect of mandibular form is whether the Mandibular Plane (obtained by placing a straight edge along the lower border of the mandible) subtends a high, median or low angle to the Frankfort Plane (formed by linking the lower border of the orbit and the supra-tragal notch). The average is 27°. A very high angle will mean that the extended mandibular plane passes through the occipital bone; a low angle occurs when the two planes are near to parallel. c) Lateral A general appraisal of the child in full face should be made, noting any gross asymmetry. (Most children have slightly asymmetrical faces and this should only be noted when there is obvious asymmetry). It is also important to note the maxillary and mandibular form, deciding whether they vary from their expected widths. This may be shown by a high vault to the palate, posterior lateral crossbite or fanning of the incisors. 6. Soft Tissue Patterns A - LIPS a) At rest - A general appraisal should be made of the shape of the lips and their posture at rest. Note particularly whether the upper lip is really short from the columella to the vermilion border (red margin). It should almost cover the upper incisor teeth. Note the thickness of the lips. If the lips do not form an anterior oral seal at rest they are described as 'incompetent' unless they are merely separated by proclined upper incisors and are of sufficient length to come together when the dental interference is removed. Such lips are described as 'potentially competent'. Only rarely are lips which are sufficiently long to be competent, habitually apart through enforced mouth-breathing due to nasal congestion. It is most important to note at rest the position of the inner border of the lower lip in relation to the labial surface of the maxillary incisors. This will affect the prognosis for stability of the upper labial segment following overjet reduction. 9
  11. 11. b) The lips in function - Note should be made of any excessive circumoral contraction during swallowing and any particular habit. If the lower lip is very taut in expressive behaviour in Class II cases, special note should be made of this. It is useful to run a finger round the labial sulci to get some idea of the tautness of the labial musculature. c) The type of anterior oral seal should be determined i.e. lip to lip with or without circumoral contraction, lower lip to palate, lower lip to tongue, lips together and mandibular posture. B - TONGUE a) At rest - It is difficult to make an accurate description of tongue size but an obvious disparity in size of mouth and size of tongue should be noted. It is again difficult to assess tongue resting posture but special note should be made if it is constantly resting forward against the lower lip between the teeth. b) Function - Special note should be made if the tongue not only rests forward but thrusts forwards to contribute to the anterior oral seal in swallowing and is placed interdentally during 's' sounds. C - MANDIBULAR PATH OF CLOSURE Normally this should be from its resting position by a simple hinge movement with a rotation of the condylar head in the glenoid cavity to a position of maximal cuspal interdigitation. Certain Class II division 1 and division 2 cases habitually posture their mandibles in a forward position - thus closure initially appears to require an upward and back movement (mandibular 'deviation'). True distal 'displacement' of the mandible following an initial contact is rarely seen. In patients showing lateral narrowness of the maxillary arch and in Class III type incisor relationships, it may be possible to demonstrate an initial contact of the cheek or incisor teeth followed by a lateral and/or forward mandibular ‘displacement’. This must be excluded or noted in all cases where teeth are in crossbite. D - SPEECH It may be possible to demonstrate an anterior air escape as with some lisping speech (anterior sigmatism) especially during the 's' sound. In Class II division 1 types a lateral air escape may be noted. 7. Oral Examination A thorough examination is made of the teeth and intra-oral soft tissues. It is particularly important to estimate the prognosis of teeth which have been heavily restored or which require restoration. This will perhaps point to the most desirable teeth to be extracted where extractions are required as part of the plan of treatment. Any dubious teeth must be checked for vitality. Using the dental chart: - a) Note teeth present in the mouth (watch for supplemental maxillary laterals and missing lower incisors). b) Caries - Mention when necessary the quality of the previous conservation and identify the rate of onset of caries. c) Report on oral hygiene and periodontal condition, noting areas of plaque retention or any excessive mobility or pocketing. d) Lower arch Labial Segment. L.L.S. - Lower Labial Segment 10
  12. 12. Note the inclinations of the upper incisors to the Frankfort Plane (approx. 108º ideal) and the lowers to the Mandibular Plane (approx. 90° ideal). Crowding/Spacing and rotations should be identified. For rotations, describe the direction e.g. mesio-palatal, disto-buccal etc. and the degrees that the tooth is rotated from the line of the arch. (Rotations are described by the approximal surface that is furthest from the line of the arch). e) Upper arch ULS - Upper Labial Segments UBS - Upper Buccal Segments Note individual rotations, tilting or drifting. Observe the presence of crowding or spacing. Relationships of Labial Segments f) O.J. - Overjet It is necessary to assess whether the antero-posterior incisor overjet is within normal limits (2-4 mm), increased, decreased, edge-to-edge or reversed (which is also described as an anterior crossbite). g) O.B. - Overbite Note should be taken as to whether the vertical incisor overbite is normal (normal being that the upper incisors overlap the lowers by one-third to one-half of their clinical crowns). The overbite may be increased, decreased, edge-to-edge or there may be a frank anterior open bite. When a positive overbite exists but there is no contact by the lower incisors onto teeth or palate, this is an incomplete overbite - contact produces a complete overbite. With a greatly increased overbite there may be contact of the lower incisors with the palatal gingivae or the upper incisors with the lower labial gingivae (traumatic overbite). h) C.L. - Centre Lines Note should be made as to whether the upper and lower centrelines are coincident with each other and whether this is in the centre of face or off to one side. If the centrelines are not coincident then record which one is incorrect and in which direction it is incorrect. i) 6s - (Buccal Segment Relationships) 6's - Classify the relationship of the first permanent molars in occlusion. If these are missing, or when the malocclusion is complex, then use the premolar or refer to the canine relationship. Angles classification of Class I, II or III is used. Intermediate occlusal positions may be referred to as half way towards the next 'full' relationship (e.g. half-unit Class II first molar relationship - one unit equals width of a premolar). j) B.S. OCCLUSION Buccal Segment Occlusion. The bucco-lingual relationship of the cheek teeth may be disturbed. Crossbites will be noted where one or all of the teeth in the lower buccal segment occlude buccal to the buccal cusps of the upper counterparts. The condition may be unilateral or bilateral. In rare instances the lower buccal segments may occlude completely palatal or buccal to their antagonists (scissor bite). Always check for a mandibular displacement (see note 3C) whenever a posterior crossbite is present. Special In-course assessments 11
  13. 13. a) Dental - Vitality tests and further procedures to determine the prognosis for the long-term retention of decayed or well filled teeth (may need further information from patient's dental practitioner for this). b) Advisability of reference for opinion of Speech Therapist, Physician, ENT Surgeon. 8 Report of Radiographs As a routine, radiographs should be taken of all areas where teeth are unerupted, together with an occlusal view of the anterior part of the upper arch. The main objective of radiographs taken prior to the formulation of a treatment plan are to ascertain - a) Whether the full complement of permanent teeth is developing (especially looking for missing 5's, 2/2 and 8's). b) The position, angulation and form of unerupted teeth e.g. upper canines, lateral incisors having deep cingulum pits and dilacerated teeth. c) Presence of a wide maxillary midline sutural space and possible patent interpremaxillary suture. d) Presence of active or recurrent caries and/or any periapical lesions. e) Other conditions - with special reference to unerupted supernumeraries in the maxillary incisor region. f) Cephalometric analysis. At present the routine is to take a DPT though in general dental practice, with a routine dental x-ray machine, it is possible to produce a standard occlusal of the upper incisor region and rotated oblique lateral jaw films (bimolars) which should show the 8 - 4 in each quadrant. 9 Attitude of Parents a) To establish whether parents comprehend the nature of orthodontic treatment and whether they want it for their child and are likely to see it through. b) Attitude of patient and whether he/she wants orthodontic treatment. 10 Conclusions A Case Description or SUMMARY - A short description of the case type, mentioning - i Angles incisor classification - Class I, Class II division 1, Class II division 2, Class III - If these are not suitable then describe more fully in terms of overjet and overbite. ii Skeletal pattern - Skeletal I, II or III - Include the vertical dimension if this varies greatly from the average figures. iii Crowding if present and site. iv Any obvious local factors e.g. missing teeth etc. B Aetiology or FACTORS - which have contributed to the malocclusion; i.e. a) Dental Base Relationships - In any of the three spatial planes. 12
  14. 14. b) Soft Tissues - Noting to what extent these have either contributed to or compensated for the malocclusion. c) Dento-alveolar disproportion (Disproportion between arch sizes and number of teeth) - It is important to assess whether there is potential crowding or spacing. Few patients are able to accommodate all 32 teeth in good alignment. Assessment of potential crowding can be helped by deciding whether there is good length of jaw. Crowding is primarily due to anterior-posterior shortness of the jaw. If there has been any premature loss of deciduous teeth the degree of space closure by mesial movement of posterior teeth and some migration round the arch of anterior teeth, will give any indication of the degree of potential crowding present. Although it may be helpful to measure spaces against the width of successional teeth, such is the variation in tooth size that this is of dubious value. d) Local Factors - e.g. supernumeraries, habits etc. C Aims of Treatment (Theoretical) - Main objectives of treatment such as - a) Limit treatment to deal with crowding only b) Retraction of maxillary incisors within lower lip activity c) Tilting of proclined incisors to compensate for a skeletal discrepancy. d) Tilting of normally inclined teeth would be unacceptable. D Treatment 1 Decide if an extraction or non-extraction case. 2 Enumerate stages of treatment - if necessary give the various lines of treatment that may be considered. 3 Give details of types of appliances. E Prognosis As accurate as possible a forecast of the ultimate effects of treatment and some opinion as to the final stability of the case and factors which might affect it e.g. upper incisors within control of the lower lip following reduction of the overjet. 13
  15. 15. INFORMATION HANDOUTS AVAILABLE IN THE DEPARTMENT TO GIVE TO PATIENTS Handout 1 - A GUIDE TO ORTHODONTIC TREATMENT Ref:HOT/UGO/STO/90/5 When necessary, orthodontics aims to improve the position and appearance of the teeth and face. The treatment also helps to ensure the long-term health of the teeth and gums. The treatment is rarely very simple or quick and perfectly straight teeth are not necessarily obtainable, though considerable improvement is the usual outcome of the treatment. The following notes will help to give you some idea of what is involved in a course of orthodontic treatment. They are general and if you need further details, please do not hesitate to ask. N.B. Due to current NHS arrangements, not all referred patients can be accepted for Hospital orthodontic treatment. Treatment Timing Active treatment is usually first considered at about the ages of 10 to 12, since by then most of the adult teeth are present. In some cases earlier treatment may be needed. Adults can also have treatment although the objectives will be different and progress may be slower. Planning Treatment Consideration of possible orthodontic treatment cannot begin without first obtaining detailed information. At an initial appointment we generally take radiographs, photographs and dental impressions (to make a mould of the teeth). A further appointment will be made to be seen on a 'Consultant Clinic' when the full assessment is completed and any necessary treatment will be explained to you. Duration of Treatment The time taken for orthodontic treatment is variable. Although some very simple treatment may last only a short while, routine treatment could take between one to three years. During treatment you will generally be required to attend appointments regularly once a month, and return between appointments if the brace breaks or cannot be worn. At the end of treatment it is likely that simple 'retaining' appliances will be inserted, to allow the teeth to settle well in their new positions. The necessary check appointments at that stage are not as frequent as during active treatment. Requirements Success of orthodontic treatment does not depend solely on the skill of the dentist, but also on the parents, and especially the patient who has to carry out the dentist's instructions. Without both encouragement and enthusiastic co-operation, a good result is unlikely. The requirements of routine orthodontic visits will involve loss of time from school or work. Before deciding on treatment you will need to make arrangements for regular leave of absence from school or work throughout the full course of treatment. Bear in mind that the appointments will occur each month, on the same day of the week, during normal working hours, Monday to Friday. Waiting Lists Once you decide to accept treatment, the commencement will be delayed until your name reaches the top of our treatment waiting lists. 14
  16. 16. Extraction of Permanent Teeth It may be necessary to have certain permanent teeth extracted as part of the treatment. This is usually because the jaws are not large enough to hold all the teeth. The space created by their loss will allow the remaining teeth to be straightened. Usually the extractions are carried out by your own dentist, but in certain cases an overnight stay in hospital may be needed. Appliances Treatment will usually involve the wearing of an orthodontic appliance (brace) inside the mouth. The brace may be fixed to the teeth and only removed by the dentist at the end of treatment. Alternatively a removable brace is provided, which is worn day and night but only removed for cleaning. When wearing an appliance it will be important to carry out all instructions, particularly those concerning cleaning of the teeth and gums. As well as needing to attend by appointment for the regular visits when the brace is adjusted, you will also have to return swiftly between appointments, during the working hours of 9.30 - 12 or 2 - 4, Monday to Friday, should the brace break or cause serious discomfort. Treatment is generally provided free of charge. If, however, an appliance is carelessly damaged or lost, a charge may be made for its replacement. Appointments It is necessary to be on time for your appointments as the dentist carrying out your treatment works to a close appointment system. On our part, we shall do our best not to keep you waiting. When under Treatment At each visit a further appointment will be given to you. This will represent the appropriate period of time that the appliance may be left safely, before further adjustments must be made. When it is not possible to keep an appointment you will need to contact and inform your orthodontist, as soon as possible, to re-arrange the next visit. Remember it is most important, if problems occur, to return between appointments for corrections to be carried out. General Dental Treatment If you have been sent by your dentist for orthodontic treatment, it is essential that you continue to attend your own dentist at regular intervals for routine inspections and any necessary fillings, etc. Alternatively, please remind us regularly, if your general dental care is also under our supervision. ORTHODONTIC DEPARTMENT FLOOR 22, GUY’S CAMPUS TOWER LONDON BRIDGE SE1 9RT 0207 955 4037 15
  17. 17. CEPHALOMETRIC RADIOGRAPHY Cephalometric radiography is one of the standard diagnostic tools in orthodontics, it is used:- 1) To help PLAN certain treatments 2) To EVALUATE treatment changes 3) As a tool for RESEARCH AND COMMUNICATION between clinicians. Clinically, cephalometric analysis is of value in:- (a) helping to assess facial form (especially the dental base relationships), (b) as an aid to treatment planning, (c) to evaluate the extent to which any changes that occur are due to growth or treatment. Cephalometric radiography was described in simultaneous publications by Broadbent and Hofrath in 1931. It involves radiographs being taken under standardised conditions, so that the measurements recorded can be compared between different patients and between the same patient at different times. The patient's head is held in position with specially constructed ‘ear posts’ in apparatus termed a 'Cephalostat'. Each time a patient is seated in the apparatus, the x-ray tube, the mid- sagittal plane of the patient's head and the film are held at fixed distances. The central ray from the x-ray tube is through the ear posts, which have been constructed to incorporate two radio-opaque circles of different diameter. If the patient's head is correctly positioned within the Cephalostat, on the resulting radiograph the ear posts will show as concentric circles. There is no manufacturer's agreement on the exact distances between x-ray tube, mid-sagittal plane and film. Thus the degree to which the image has been magnified during this type of radiographic process must be determined if there is a need to compare films taken on different machines. When the patient is positioned within the cephalostat, it is therefore important that:- 1) The ear posts are not deflected and lie completely within the ear canals. 2) The patient's Frankfort plane is viewed as being horizontal i.e. parallel to the floor. 3) The teeth are generally held in the intercuspal position. [Where a mandibular displacement has been previously recorded, a request can be made for the mandible to be also positioned in centric relation, to record the teeth in their initial contact position.] 4) The lips should be in a relaxed, habitual position. Figure 1 shows the general relationship of film, patient's head and tube for cephalometric radiography. Cephalostat Figure 1 Tube Central Ray Film 5ft 1ft BASIC CEPHALOMETRIC ANALYSIS 16
  18. 18. It is conventional to trace the lateral cephalogram with the patient's head facing to the right. The radiograph should show both hard tissue detail and the soft tissue profile. (The shadows of the metal rings within the ear posts should appear as concentric circles.) TRACING The film is placed on a viewing box and, once satisfactorily orientated, it is secured with sellotape. The film is then covered with tracing paper which is also secured with sellotape. Various hard tissue structures and the soft tissue profile are traced. These include:- 1) The outlines of the mandible and maxilla 2) The outlines of the most prominent upper and lower incisors and first permanent molars 3) The base of the skull (sella turcica, nasal and frontal bones) 4) The lower border of the orbit and external auditory meatus (or the porion as identified from the position of the ear posts) The face is often not perfectly symmetrical and there is usually some discrepancy in the magnification between the two sides of the head, producing two sets of outlines for the mandibular border and orbit. When two shadows of a structure are seen, (such as the left and right aspects of the lower border of the mandible) then both are traced, and any landmark, (e.g. gonion) is taken as midway between the two points. The cephalometric landmarks to be used later in an analysis of the radiograph are identified on the tracing. It is bad practice to mark these locations on a radiograph since this will bias any subsequent repeat measurements. The commonly used landmarks that have been agreed are a compromise between the tracer's ability to reproduce them repeatedly and accurately, and the validity of the anatomical sites chosen. However, rigid definition of the landmarks are essential if the results are to be validly reproducible between different tracers. Commonly used landmarks are shown with their definitions printed in Appendix I at the end of these notes. There are many different cephalometric analyses, some of which have received international acknowledgement. Such an analysis is a collection of measurements, ideally associated with a set of normal values, which aims to compress the cephalogram information into a form that can be used for evaluating clinical assessment and treatment planning. It is not meant to provide a set of figures as an objective for treatment. ANALYSIS 1. Antero-Posterior Dental Base Relationship (Skeletal Pattern) There are many ways of determining the skeletal pattern. One of the simplest is to measure the angles SNA/SNB. SNA/SNB Difference (sometimes referred to incorrectly as Down's Analysis) 17
  19. 19. Points A and B have been taken as the anterior limit of the dental bases. The relationship of these to the anterior cranial base (S-N line) can be determined. Thus the angles SNA and SNB will measure the position of the maxilla and mandible relative to the anterior cranial base. The difference between these angles (ANB) indicates the jaw relationship: Angle ANB 5º or > Skeletal base II 2-4º Skeletal base I 1º or < Skeletal base III N S Figure 3 SNA/SNB A B The ANB assessment is quick and simple but has the disadvantage that the angle ANB can vary with vertical or horizontal positioning of sella or nasion in the skull. Thus the further that the patient's SNA angles varies from 82º (+ 3º) the more inaccurate becomes the interpretation of the values of the ANB angle! As a crude rule of thumb, if SNA departs from 82º, a correction (termed the Eastman correction) can be applied. [N.B. For every degree that SNA is above 82º, subtract ½º from the angle ANB. For every degree below 82º add ½º to ANB. This compensation becomes less valid as SNA departs greatly from 82º.] The mandibular plane is drawn between menton and gonion. The lines of the maxillary and mandibular planes should be extended on the tracing paper until they meet, and the angle between them (MMPA) measured. The average is 27º ± 4º. It is interesting to note that if this angle is significantly greater than 32º, the anterior lower facial height is usually increased. Similarly if the angle is reduced below 23º, the lower facial height is often also reduced. 2) Dental Relations: If the lateral cephalogram has been taken correctly then the incisors will be in their habitual intercuspal position. The relationship between the upper and lower incisors is noted. 18
  20. 20. The incisor relationship is defined as the relationship between the incisal edge of the lower incisors and the cingulum plateau of the upper. If the lower incisor edge lies on the cingulum plateau of the upper incisors it is Class I. If it lies posterior to the cingulum, it is Class II and if anterior, Class III. (Figure 3) Figure 3 11 1 111 The degree of overjet and overbite present is assessed clinically, but can be corroborated from the lateral cephalogram. In a normal or Class I malocclusion - THE OVERJET should be between 2-4mm (as measured from the incisal edge of the most prominent upper incisor to the labial surface of the corresponding lower incisor ) and the OVERBITE between 30-50% (as measured by the amount of vertical overlap of the lower incisors by the upper incisors. The next step is to assess the angulation of the incisors to their dental bases. This is done by measuring the angles between the long axes of the most prominent upper and lower incisors and their respective maxillary or mandibular planes. The upper incisors should make an angle of 109º± 5º to the maxillary plane and the lower incisors 92º ± 4º to the mandibular plane. If the angles are greatly increased, the teeth are proclined. If reduced, retroclined. When the incisors are in a Class I relationship the interincisal angle formed by the intersection of the long axes of the upper and lower incisors should be 130º ± 5º. BALLARD'S CONVERSION Another method of determining the skeletal pattern involves a geometrical formula and is termed a Ballard "Conversion Tracing”. This uses the maxillary plane, the mandibular plane and the shadows of the most prominent upper and lower central incisors. Lines are drawn through the long axes of these incisors and extended to their respective basal planes (Maxillary and Mandibular planes). The angles made by these teeth are noted. On a superimposed second tracing the upper incisor is then tipped to its ideal inclination of 109º, by moving this tooth about a point on its long axis, that is one-third of its length from the root apex. The lower incisor is similarly tipped about a point one-third of its length from the root apex. [Its exact angulation will vary inversely with the value of the maxillary-mandibular planes angle (MMPA). The lower incisor to mandibular plane and the MMPA need to total 120º and knowing this one can calculate the value for the angle of the lower incisor to the mandibular plane]. The long axis of the lower incisor in its new 'ideal' position is adjusted as discussed and then projected until it meets the upper incisor. These theoretical geometrical procedures have removed any dental compensatory inclination from the teeth. The relationship of the line through the lower incisors and precisely where it meets the upper incisor long axis indicates the skeletal relationship (see Figures 2 and 3). 19
  21. 21. Figure 4 Ballard’s conversion tracing showing a Class II division 1 incisor relationship on a Skeletal I dental base (The shaded teeth have been “corrected” to their ideal angle - shown by the dotted lines) 3) Vertical Dental Base Relationship: The Frankfort plane is taken as a line through orbitale and porion (porion is often identified by the ear post position!) Since both orbitale and porion can be difficult to identify, the maxillary plane (ANS-PNS) is commonly used instead to represent the inclination of the maxilla. [The Frankfort and maxillary planes were assumed to be approximately parallel but there is in fact a marked individual variation and the maxillary-mandibular planes angle needs to be measured accurately each time] INTERPRETATION OF THE ANALYSIS As a result of the above, we have established: SNA 82º ± 3º ] SNB 78º ± 3º ] This gives the anterior/posterior skeletal base relationship ANB 3º ± 2º ] MMPA 27º ± 4º ] Maxillary/Mandibular Planes Angle gives the vertical skeletal relationship 1 Mx Pl 109º ± 6º ] The degree of proclination / retroclination will indicate the type of tooth 1Md Pl 92º ± 6º ] movement that treatment should involve 1 to 1 130º ± 5º ] The interincisal angle should ideally be around 130º ± 5º at the end of treatment for stability of the incisor relationship. 20
  22. 22. Cephalometric Landmarks S - Sella turcica. The midpoint of the pituitary fossa as determined by inspection. N - Nasion. The most antero-inferior point on the frontal bone at the nasofrontal suture. ANS - Anterior nasal spine. The tip of the anterior nasal spine as seen in the lateral skull radiograph. A - A point (sub-spinale). The deepest point on the curvature of the surface of the maxillary bone between ANS and the alveolar crest of the upper central incisor. B - B point (supra-mentale). The deepest point on the curvature of the anterior border of the mandible between pogonion and the alveolar crest of the lower central incisor. Po - Pogonion. The most anterior point on the bony chin in the midline. Me - Menton. The most inferior point on the mandible at the symphysis. Go - Gonion. The lowest point on the curvature of the angle of the mandible where the body of the mandible meets the ramus. Where bilateral images of the mandible occur, a mid-point between the right and left images should be constructed. PNS - Posterior nasal spine. The tip of the posterior spine of the palatine bone in the hard palate. P - or Porion. The highest point on the bony external auditory meatus. If both sides are visible, the midpoint is taken. Or - Orbitale. The most inferior point on the margin of the orbit. If two orbital shadows are visible, the midpoint is taken. Frankfort Plane (Porion-Orbitale). This plane is described as being horizontal when the head is in a free postural position. There is, in fact, considerable individual variation and its defining points are difficult to identify. For this reason it is more conventional to use the: Maxillary Plane. This plane is constructed by drawing a line from the anterior to posterior nasal spines. This plane is not usually parallel to the Frankfort plane. Mandibular Plane (Gonion-Menton). A variety of mandibular planes have been described but one of the most commonly used is the line from gonion to menton. It requires the construction of gonion. Functional Occlusal Plane (FOP). A line passing through the occlusion of the premolars (or deciduous molars) and the first permanent molars. The cuspal outlines of these teeth may be unclear and this plane may be difficult to define, particularly in the mixed dentition. 21
  23. 23. Classification of Occlusion and Malocclusion IDEAL OCCLUSION Rarely exists in contemporary populations. However for the purposes of diagnosis, defining treatment goals and for evaluating treatment outcome, an appreciation of the features of ideal occlusion is required. 1. The line of occlusion passes through the central fossae and along the cingulae of the maxillary teeth and through the buccal cusps and incisal edges of the lower teeth. 2. Approximal tooth contacts are tight, with level marginal ridges, and there are no rotations. 3. The distobuccal cusp of the maxillary first permanent molar occludes with embrasure between the mandibular first and second permanent molars. 4. There is a flat occlusal plane or slight curve of Spee. 5. The long axes of the teeth, except the mandibular incisors, have a slight mesial inclination (i.e. the crowns are more mesial than the roots). 6. The crowns of the posterior teeth (canine to molars) have a lingual inclination). COMMONLY USED CLASSIFICATIONS AND INDICES Angle’s classification • Only internationally recognised classification of malocclusion • Based on the premise that the first permanent molars erupted into a constant position with the facial skeleton. This is incorrect. • 3 groups according to the anteroposterior relationship of the dental arches. Vertical and transverse malrelationships not included. Angle’s Classification: Class I or neutrocclusion - the mesiobuccal cusp of the upper first molar occludes with the mesiobuccal groove of the lower first molar. Class II or distocclusion - the lower first molar occludes distal to the Class I position. Postnormal relationship. Class III or mesiocclusion - the lower first molar occludes mesial to the Class I position. Prenormal relationship. British Standards Institute classification Based upon the incisor relationship Class I. The lower incisor edges occlude with or lie immediately below the cingulum plateau of the upper central incisors. Overjet = 2- 4 mm. Class II. The lower incisor edges lie posteriorly to the cingulum plateau of the upper central incisors. There are 2 subdivisions. Division 1. The upper incisors are proclined or of an average inclination and there is an increase in overjet. i.e. 5 mm or more. Division 2. The upper central incisors are retroclined. There may or may not be an increase in overjet. i.e. maybe 2-4 mm or 5 mm or more. Class III. The incisal edges of the lower incisor lie anterior to the cingulum plateau of the upper incisors. The overjet is reduced or reversed. i.e. 1 mm or less including negative values. INDICES OF MALOCCLUSION Neither Angle’s nor the incisor classification provide a measure of the severity of malocclusion. Different methods are required for estimating (i) prevalence of malocclusion in a population, (ii) treatment priority (iii) treatment success and (iv) investigating the relationship between malocclusion and various aspects of dental health. The World Health Organisation (1977) proposed requirements for an ideal index: (i) reliable and reproducible, i.e. does the index give the same result when recorded on two different occasions and by different examiners? (ii) valid, does it measure what it is supposed to measure? (iii) Should be acceptable to professionals and public. (iv) Should require a minimum of judgement to apply it successfully (v) Should be administratively simple. However few orthodontic indices have been thoroughly tested. Quantitative Assessment of Malocclusion Indices are used and two separate approaches can be employed. Either 1) Each feature of the malocclusion is given a score, or 2) The worst feature of a malocclusion is recorded (e.g. the Index of Orthodontic Treatment Need). Indices of Malocclusion Summers occlusal Index- develop in 1960s for research. Good reproducibility The index scores 9 parameters including overbite overjet, posterior crossbite, median diastema, absent upper incisors, tooth displacement. Index of Orthodontic Treatment Need (IOTN) - used to determine the impact of a malocclusion on an individual’s dental health and psychosocial well being It comprises 2 elements. Dental health component and Aesthetic component. Indices of Treatment Need Aim is to rank occlusal disharmonies according to their severity. The index can be used for epidemiological purposes and to establish priorities of treatment. Examples are the Handicapping Malocclusion Assessment Record (HMAR; Salzmann, 1968), and the Occlusal Index (OI; Summers, 1971). The HMAR allocates points for dental irregularities and arch malrelationships, which are multiplied by a weighting factor before the total score is assigned. This can be done either from orthodontic models or clinically with the patient. The OI scores dental age, molar relationships, overbite, overjet, posterior crossbite, tooth displacement, missing upper lateral incisors. More complicated than HMAR but more reliable. Index of Orthodontic Treatment Need Dental Health Component- The single worst feature of a malocclusion is noted (the index is not cumulative) and categorised into one of five grades reflecting need for treatment. Grade 1-no need, Grade 2- little need, Grade 3 -moderate need, Grade 4 -great need, Grade 5 - very great need. Aesthetic component- developed in an attempt to assess the aesthetic handicap posed by a malocclusion and thus the likely psychosocial impact upon the patient. The aesthetic component comprises a set of ten standard photographs which also grade from score 1, the most aesthetically pleasing to score 10, the least aesthetically pleasing. Score 1 or 2-none, 3 or 4 slight, 5,6, or 7 moderate, 8,9,10 - definite. Disadvantage- subjective and no Class III or open bite photographs. Indices of Treatment Change To evaluate the quality of treatment provided. The OI has been used and gives reliable and valid results. The Peer Assessment Rating Index (PAR) was developed for use in the British National Health Service (Richmond et al., 1990). Scores are listed for a number of parameters before and at the end of treatment, using study models. Unlike IOTN, the scores are cumulative and a weighting is applied to each component to reflect current opinion in the UK as to their relative importance. By applying pre and post treatment scores to a nomogram three categories of judgement can be obtained for all types of malocclusion (i) great improvement; (ii) moderate improvement; (iii) no change. Appendix Page 1
  24. 24. Development of the Dentition and Occlusion Normal Dental Development - normal means average rather than ideal. A knowledge of what constitutes the range of normal dental development is essential. A knowledge of both calcification and eruption times is essential for determining (i) dental as opposed to chronological age and (ii) whether a tooth not present on radiographic examination can be considered absent. Development of the deciduous dentition The neonate is without teeth for 6 months and at birth the lower gum pad lies distal to the upper to a variable degree. During the first year the gum pads and dental arches widen to accommodate all the teeth. Deciduous incisors are smaller and whiter than their successors. They erupt upright and spaced - a lack of spacing indicates that the permanent successors will be crowded. The overbite is increased but reduces over the next 4 years until the incisors are edge to edge which may result in marked attrition. Deciduous dentition is complete by ~3 yrs. No increase in lateral or anteroposterior arch dimensions over the next 3 yrs. Absence of lower arch crowding in the permanent dentition can only be assured if the deciduous dentition is spaced by more than 6 mm. Transition from the deciduous to the mixed dentition Classically the mixed dentition begins with the eruption of either the first permanent molars or the lower central incisors at ~ 6yrs. The first permanent molars may be guided into a cusp-to-cusp relationship by the distal surfaces of the deciduous second molars if they are flush at this stage or into full intercuspation if the lower arch has moved forwards. Growth in maxillary length is necessary to allow eruption of the first permanent molars which develop in the maxillary tuberosity and face buccally, distally and occlusally. The mandibular molars develop under the anterior border of the ascending ramus of the mandible and growth in mandibular length is required for these teeth to erupt. The replacement of deciduous teeth by their successors in the buccal segments may commence as early as 7 yrs of age and is not always complete by 12 yrs. There is a discrepancy in the total space occupied by the deciduous cheek teeth compared with that required for their successors (permanent canine, first and second premolars). The combined width of the deciduous canine, first molar, and second molar is greater than that of their permanent successors, The surplus space or leeway space as it is known, is greater in the lower arch. On average this space is 1-1.5 mm in the maxilla and 2- 2.5 mm in the mandible. This means that if the deciduous buccal segment teeth are retained until their normal exfoliation time, there will be sufficient space for the permanent canine and premolars. Teeth in the upper labial segment develop on the palatal aspect of the roots of their predecessors and erupt down, out and forwards. Except in crowded cases, when the upper central incisors erupt, a midline diastema is normally present. The upper lateral incisors develop in a more palatal position than the central incisors. Treatment is not indicated for the diastema which will gradually close as the upper lateral incisors and canines erupt. The lateral incisors are distally inclined due to pressure from the crowns of the unerupted canines. As development proceeds, the canines move buccally and should be palpable high in the buccal sulcus and this allows the lateral incisors to become more upright. The upper labial frenum should no longer be attached to the crest of the alveolar process but to its labial surface. A low attachment will interfere with space closure. The lower permanent incisors erupt before their counterparts in the upper arch. The permanent incisors are larger than their predecessors. Space is made available by: Deciduous incisors are spaced. Permanent incisors erupt more proclined. Increase in the intercanine width at this time ~ 3 mm. Lower incisors in particular, may erupt rotated and crowded as but will spontaneously align if space is made available. The permanent incisors develop behind the roots of their predecessors with the lateral incisors more lingually placed. Transition from the mixed to the permanent dentition The second deciduous molars usually erupt with their distal surfaces flush anteroposteriorly. The transition to the stepped Class I molar relationship occurs when all the deciduous teeth have been replaced and the upper first permanent molar moves mesially to a lesser extent than the lower first permanent molar. Sequence of eruption is variable. In the lower buccal segment the first tooth to erupt is either the canine or first premolar. The second premolar sometimes erupts after the second permanent molar. In the upper arch the first premolar usually erupts before the canine. The upper canine erupts into a wider arc in the same manner as the upper incisors and any remaining space between the incisors should close at this time. The second molars erupt at 12-14 yrs and third molars at 16-20 yrs. Development of the Dental Arches Intercanine width is measured across the cusps of the canines. During the primary dentition an increase of about 1-2 mm is seen. In the mixed dentition an increase of about 3 mm occurs which is complete by 9 yrs. A small decrease in labial segment crowding may occur before 9 yrs. Arch width is measured across the arch between the lingual cusps of the second deciduous molars or second premolars. An increase of 2-3 mm occurs between 3 an 14 yrs of age. Arch circumference is determined by measuring around the buccal cusps and incisal edges of the teeth to the distal aspect of the second deciduous molars or second premolars. In the maxilla there is little change but in the mandibular arch, the circumference decreases ~ 4mm because of the leeway space. Late changes in the permanent dentition Maybe an increase in incisor crowding particularly in the lower arch. Increase in the interincisal angle. Slight increase in mandibular prognathism. Factors contributing to late incisor crowding Prognathism. Mandibular growth rotations. Soft tissue influences. Mesial migration of the buccal teeth Appendix Page 2
  25. 25. AETIOLOGY OF MALOCCLUSION SKELETAL AND SOFT TISSUE FACTORS INTRODUCTION Malocclusion can occur as a result of genetically determined factors which are inherited, or environmental factors, or more commonly a combination of both. ! Studies from twins indicate that skeletal pattern and tooth size and number are largely genetically determined. ! General factors affecting occlusal development include: Skeletal factors. The size, shape and relative positions of the upper and lower jaws. Soft tissue or muscle factors. The form and function of the muscles which surround the teeth, i.e. the muscles of the lips, cheek and tongue. Dental factors. Size of the dentition in relation to the jaw size. SKELETAL FACTORS AND OCCLUSAL DEVELOPMENT Any pathological condition affecting growth of the jaws is likely to affect the occlusion of the teeth. e.g. Inherited and acquired congenital malformation, trauma or infection. Uncommon. ! Concerned primarily with normal variation, which is frequent and wide ranging. ! As the teeth are set in the jaws, the relationship of the jaws to each other will have a large influence on the dental arches. ! Skeletal relationship can be considered under 3 headings: (1) Jaws in relation to the Anterior Cranial Base (2) Jaws in relation to each other (3) Alveolar bone in relation to basal bone Jaws in relation to the anterior cranial base: The jaws are part of the total structure of the head, and it is possible for each jaw to vary in its positional relationship to other structures of the head i.e.vertical, sagittal, and transverse. • Should relate the jaw positions to the anterior cranial base. Jaws in relation to each other: This can occur in all 3 planes. • Sagittal skeletal relationship: The antero-posterior relationship (APR) of the basal parts of the jaws to each other with the teeth in occlusion is known as the or skeletal pattern. In common use, viz. Skeletal Class I - The jaws are in their ideal APR in occlusion. Skeletal Class II - The lower jaw in occlusion is positioned more posteriorly than in SkCl I. Skeletal Class III -The lower jaw in occlusion is forward of SkCl I There is a range of severity of Sk CL II & CL III. Variation in SK relationship can be due to: (a) variation in size of jaws; (b) variation in the position of jaws in relation to the cranial base • Transverse skeletal relationship: The relative sizes of the jaws in the lateral dimension also has an effect on occlusion. If the lower jaw is wider, buccal crossbite arises. If the upper jaw is too wide, lingual occlusion of the lower teeth arises. Crossbites may be unilateral or bilateral. • Vertical skeletal relationship: The vertical relationships of the upper and lower jaws also affects occlusion. The mandible with a high gonial angle tends to produce a longer vertical dimension of the face, and in severe cases an anterior open bite. The mandible with a low gonial angle tends to produce a shorter vertical dimension of the face. Alveolar bone in relation to basal bone. The term SK relationship refers to the basal bone of the jaws. The relationship between the upper and lower alveolar bones may not necessarily be the same as that between the upper and lower basal bones. Alveolar bone supports teeth and will match tooth position rather than basal bone position. However the alveolar bone and tooth positions can only differ from the basal relationship within a limited range. This is a very important factor in orthodontic treatment. The reason for the possibility of difference between alveolar and basal bone is that tooth position is not governed entirely by jaw position (see later). However it the basal bone relationship or the skeletal pattern that is the most important in occlusal development. Skeletal Relationship in Orthodontic Treatment • SK rel. is important in occlusal development and orthodontic treatment. Orthodontic treatment which is confined to tooth movement has little effect on the size, shape or relative positions of the basal parts of the jaws. Its only direct effect is on tooth position and alveolar bone position and form. As teeth must be positioned on basal bones, the SK relationship limits the amount of orthodontic tooth movement in all 3 planes of space. It may not be possible to correct CL II or CL III incisor relationships if they are based on severe SK II or SK III bases. • In practical terms, it is easy to alter the inclination of incisor teeth producing little change in their apical positions. Treatment techniques are also available which can produce apical tooth movement but because they are limited in their scope, severe SK discrepancy remains a limiting factor to orthodontic treatment. For example it would be difficult to reduce an overjet of 8mm where the teeth are in the correct inclination. The aetiology of the OJ is the severity of SK II relationship. Soft Tissues and Occlusal Development • The muscles of the tongue, lips and cheeks are of importance in guiding teeth into their final positions. • Variation in muscle form and function can affect the position and occlusion of the teeth. • These muscles have their main origin on the basal parts of the jaws and so the position of the jaws will influence muscle action. Therefore the muscles should not be considered in isolation to the jaws. • The Lips and occlusal development: consider their size, form and function. The form and function can be considered in two planes, vertical and sagittal (AP). Lip contour or form: If the lips are everted, the underlying teeth may be proclined and if the lips are vertical with no outward curve at the red margin the underlying teeth may be retroclined. The average lies between these two extremes. Lip seal: In the vertical dimension considerable variation occurs in the resting lip form. In many individuals the lips do not meet in the rest position, referred to as “labial incompetence”. The reason may be due to the shape of the jaws e.g. when a high mandibular gonial angle places the origin of the lower lip too far down in relation to the upper lip. In most cases the source of the discrepancy lies in the lips themselves which are too short in the vertical dimension or the wrong shape to meet at rest. Patients with mild lip incompetence unconsciously hold their lips together by slight circumoral contraction for a significant part of the time. Appendix Page 3
  26. 26. Lip incompetence is of greatest significance in Cl II Div 1 mal., because the ultimate stability of the corrected incisor overjet depends on a lip seal being achieved. The desire to maintain a lip seal increases until the late teens. However cases with marked lip incompetence should be given a guarded prognosis. The importance of discrepancies in vertical size of the lips lies in the fact that the lips are usually brought together during swallowing and speech movements. If they are of sufficient size then lip closure will not place extra forces on the teeth. If the lips at rest are apart then muscular contraction will be required to bring them together during speech and swallowing, which will impose extra forces on the underlying teeth. Some people whose lips don’t meet at rest, maintain a conscious lip closure, again imposing muscular forces on the teeth. The effect depends on the sagittal relationship of the lips (see below). LIP LINE: The level at which the lips meet together in normal function is usually called the ‘lip line’. It is applied only to the relationship of the lower lip to the upper central incisors. In ideal incisor occlusion the resting lower lip covers between a third and a half of the labial surface of the upper central incisors. In CL II Div 1 incisor relationship the lip line will be lower and often fail to control the upper incisors whilst in a CL II Div 2 incisor relationship the lower lip may cover the entire labial surface of the crown. In SK II relationships the lower lip may function partly or completely behind the upper incisors. If the skeletal discrepancy is not severe, the lip may procline the upper incisors so that the occlusal relationship is more severely CL II than the SK relationship. If the SK relationship is severe the lower lip may function behind the upper incisors without causing them to be proclined. In other cases of SK II the lower lip functions entirely in front of the upper incisors causing them to be retroclined into CL II Div 2. It is equally possible for lip activity to produce CL II or CL III incisal relationships on a SK I base. It is also possible for lip activity to produce either a CL I incisal relationship on either a SK II or SK III base. The sagittal relationship of the lips is determined by the relationship of the basal bone of the jaws to which they are attached. The lower lip is further back in Sk Class II and further forward in SK Class III. This may cause the lower lip to modify the eruptive path of the incisors and alter the primary effect of the SK relationship on the occlusal relationship, either increasing or decreasing the effect of any skeletal discrepancy. Tongue position and size are important in determining the occlusion of the teeth. Where the lips are incompetent the tongue will be used to produce an anterior oral seal during swallowing. This adaptive lip-tongue-alveolar process seal is used because it requires less effort. It tends to disappear as dental development proceeds. Not to much importance should be attached to an adaptive tongue thrust, however it may produce an incomplete overbite, or more severely an anterior open bite. It is seen more commonly in CL II Div 1 where the upper incisors make a lip seal more difficult. Unfortunately about 1% of individuals have a swallowing activity accompanied by tongue thrusting (endogenous tongue thrust). These individuals should be identified as orthodontic treatment will relapse. Signs: lisp, reverse curve of Spee in both arches, presence of tongue between the anterior teeth, proclined U/L incisors, tongue thrust associated with lip competence. If the tongue is too large it may prevent the full eruption of the buccal or incisal teeth resulting in open bites or incomplete overbites. HABITS AND OCCLUSION Lip and tongue sucking and pencil biting are of no significance to occlusal development. Digit sucking is of relevance. Considered as normal in infancy as 67% of children suck either a digit or dummy. Probably innate until 2 yrs. Prolongation after infancy due to learning. The effects on the dentition depends on the persistence of the habit and partly on the favourability of the soft tissues. • Commonly the presence of a thumb between the erupting teeth causes either an incomplete overbite or an anterior open bite which is usually asymmetrical. • There is often an increase in the overjet due to proclination of the upper incisors. • The upper arch is narrowed by pressure from the cheeks on the buccal teeth. As both arches are of equal width, there is often a lateral displacement of the mandible into the position of maximum occlusion causing a unilateral crossbite. These defects will disappear if the habit ceases by 7-8 yrs and it is the sole causative factor. Should not underestimate the effects of prolonged and persistent sucking habits. The degree of disturbance in the incisor region is in proportion to the time, force and manner in which the digit is sucked. Management of digit sucking: Attempts to stop thumb or finger sucking usually fail unless the child wishes to stop, in which case the fitting of any appliance after 8 yrs is usually sufficient. • Parents should be discouraged from nagging as it is counterproductive. • Drastic measures to break the habit are inappropriate. • Few children persist in the habit to the point where the behaviour justifies psychological investigation. • Dummy sucking causes mild AOB of primary dentition and is transient. NEUTRAL ZONE AND OCCLUSION Once the teeth have erupted, all the forces acting upon them are equalised to maintain them in a stable position known as occlusion. The muscular forces acting directly on the teeth, that is the muscles of the lips, cheeks and tongue must be in balance if the teeth are to remain in a position of stability. The fact that the lips and cheeks function outside and the tongue within the dental arches has led to the concept of a ‘neutral zone’ existing between the inner and outer perimeters of the dental arches, where the forces of the lips and cheeks are balanced by those of the tongue and within which the teeth are positioned. The Neutral Zone, must be considered not only in relation to muscle forces but also in relation to intra-oral pressures which are induced by mandibular positions, and to occlusal contacts and the integrity of the periodontal ligament. As muscle form and function is to a large extent genetically determined, alteration of muscle activity at a subconscious level by education is difficult. Therefore not only are the teeth positioned in a neutral zone of the oral environment as a result of development, but they must also be in a neutral zone at the end of orthodontic treatment, otherwise they will move to take up other positions. This neutral zone has been called a position of ‘muscle balance’ but it probably involves more than muscle pressures. Changes during growth can affect the muscular environment of the teeth as well as the size and relationship of the jaws. If the lips do not meet at rest there is a tendency for them to remain apart during childhood but to be held together by muscular activity progressively more as the child grows. This puts more pressure on the incisor teeth. Appendix Page 4
  27. 27. AETIOLOGY OF MALOCCLUSION LOCAL FACTORS Introduction General factors are considered to be determined genetically and cannot be intercepted to any great extent. Local factors produce a local disturbance in dental development that becomes more severe the longer it continues to operate. Local factors are much less frequent than general factors however they are superimposed on general factors and may provide additional complications to occlusal development. Alternatively, a local abnormality may be the only modifying feature present in an individual, the effect of the general factors being favourable. CLASSIFICATION OF LOCAL FACTORS • Variation in tooth number. • Variation in tooth form. • Aberrant developmental position of individual teeth. • Local abnormalities of soft tissue. • Local pathology. ! VARIATION IN NUMBER OF TEETH 1) Supernumerary teeth: one that is additional to the normal series. Occurs in the permanent dentition in 1-2% of the population and in the primary dentition in < 1%. A supernumerary in the primary dentition is often followed by a supernumerary in the permanent dentition. Result from excessive but organised growth of the dental lamina. Most frequent in the upper incisor region and are more common in males. Appear to be an inherited feature. There are 3 main types of supernumerary teeth in the permanent dentition • Supplemental teeth: extra teeth of normal form and occurs at the end of a tooth series, the most common being the lateral incisor. It is less common to find supplemental premolars and molars, except in Asian and African populations. • Conical teeth: the typical conical supernumerary occurs in the premaxilla, near the midline, and is often called a mesiodens. It may occur singly or in pairs. It is sometimes inverted, in which case it does not erupt. • Tuberculate: this type also occurs in the premaxilla, but is different from the conical tooth in form, position, behaviour and time of development. It is a later development than the conical tooth, its root developing later than the permanent upper central incisor. It appears on the palatal aspect of central incisors and does not normally erupt in childhood. It may be uni or bilateral and classically it prevents eruption of a permanent tooth. • Odontome: Rare. Both complex and compound forms. Effects of supernumerary teeth and their management I. Failure of eruption: The presence of a supernumerary tooth is the most common reason for the failure of eruption of a maxillary permanent incisor. However, failure of any tooth in either arch can be due to a supernumeray tooth. Management involves removing the supernumeray and ensuring that there is sufficient space to accommodate the unerupted tooth. It is advisable to bond a gold chain to the unerupted tooth at the time of removing the supernumerary so that traction can be applied to the unerupted tooth if necessary. II. Displacement: Can cause displacement or rotation of an erupted tooth. Management involves removal of the supernumerary and fixed appliances. A conical supernumerary may also cause a median diastema. Treatment involves removal of the supernumerary and localised tooth movement. III. Crowding: This is caused by the supplemental tooth and is treated by removing the most poorly formed or displaced tooth. IV. No Effect: Occasionally a supernumerary tooth (conical) is found as a chance finding on a radiograph. Usually symptomless and can be left in situ under radiographic examination if they are inaccessible. They are removed if there are signs of enlargement of the follicle, with potential cystic formation around the crown and also if orthodontic tooth movement is required. 2) Gemination: Gemination of permanent teeth is not very common. Usually upper or lower incisors are affected. Treatment depends on the degree of crowding caused. • Where there are a normal number of incisors and gemination appears to be the merging of 2 of these teeth, no treatment may be required. • An increase in the number of incisor crowns caused by a true gemination will usually cause crowding. This can present a difficult aesthetic problem. May need to extract the tooth and provide a prosthetic replacement. 3) Hypodontia: Developmental absence of one or more teeth from the dentition, is not common occurring in about 6% of European populations. Total anodontia is rare. Hypodontia is inherited. MISSING UPPER LATERAL INCISORS. Incidence 2%. If one is absent the other may be of normal size but is often small and conical. Of importance is the effect of the absence of this tooth on the eruptive path of the maxillary canine, which frequently becomes displaced palatally. The local problem caused by a missing lateral incisor varies according to the arch size and relationship. • In a crowded arch the permanent canine may erupt into contact with the central incisor. If the canine is not too pointed, a reasonable aesthetic result may be obtained by reducing its tip. • In the average to large arch spacing can be dealt with in several ways. a) Minimal spacing may be acceptable to the patient. b) Sufficient space for a bridge can be made by retracting the canine. c) Sometimes the space is too small to accommodate a reasonably sized pontic. The options available are:- i) Create space by distal movement of the upper buccal segments or extract a premolar tooth ii) Closure of the anterior spacing by forward movement of posterior teeth. • Where there is a CL III incisor relationship and missing upper lateral incisors, advancement of the upper labial segment tends to open up space further so that a pontic may be necessary. • In crowded cases serious consideration should be given to transplanting the premolar tooth into the site of the missing incisor. Appendix Page 5
  28. 28. MISSING LOWER CENTRAL INCISORS- Uncommon. Incidence 0.5%. Management: • In uncrowded cases an acid etch retained bridge can provide a satisfactory solution. • In crowded cases space can close although a fixed appliance will be required. Absence of lower incisors can have an adverse secondary effect on the upper labial segment because of the difficulty of arranging 6 upper teeth around 5 or 4 lower teeth. Crowding will appear in the upper labial segment unless there is an increased overjet or the upper lateral incisors are diminutive. In other cases it will be necessary to accept a disruption in the buccal occlusion to maintain incisor alignment. MISSING PREMOLARS- Incidence 5 % lower and 2% upper. • The fact that lower second premolars and less frequently upper second premolars may be missing makes it essential to take radiographs before extracting permanent teeth to relieve crowding. • Lower premolars can develop late and should not be assumed to missing until 9 yrs. • If the arch is of ample size the second deciduous molars that are not resorbing may remain in place until 30-40 yrs unless they are submerging or are of poor quality. MISSING LOWER THIRD MOLARS- absence of these teeth has little adverse effect on the developing occlusion and may be of some benefit as impactions are common and there may be less chance of later deterioration in incisor alignment. • Second molars should not be extracted before the presence of third molars has been confirmed. Third molar development is variable 7-14 yrs. TEETH OF ABNORMAL FORM DENS-IN-DENTE (tooth within a tooth)- where the lateral incisors are small and conical it is important to check radiographically whether this abnormality, produced by a coronal invagination, is present. The deep cingulum pit leads into a cavity with a deficient enamel lining, which enables bacteria to gain access to the pulp. DILACERATION-this term describes an abnormal angulation between the crown and the root or within the root. The site of deformation depends on the timing of the disturbance during the tooths development. Usually due to trauma to the deciduous tooth, but sometimes there is no history. Treatment, extract or align if mild. ABERRANT DEVELOPMENTAL POSITION OF INDIVIDUAL TEETH The developmental position of any tooth, before it erupts into the mouth, may be such that it cannot erupt into its correct position Teeth most commonly affected are the upper canines, lower third molars, upper central incisors and lower lateral incisors. Maybe the result of crowding, trauma or unknown aetiology. ! Trauma affecting developmental position- Upper central incisors are most commonly affected. History of trauma to deciduous incisors at 4-6 yrs. When there is no history of trauma and there is no dilaceration, the tooth may be congenitally displaced. ! Ectopic upper canines • The upper canine is particularly liable to develop ectopically due to its long path of eruption from under the orbital floor. • Prevalence is about 2%. • The tooth commonly becomes deflected palatally, and the deciduous canine is retained. More rarely it becomes grossly displaced lying horizontally near the floor of the nose. • There is an association between small or absent lateral incisors and ectopic eruption of canines. If the canine crown isn’t detected as a bulge high in the buccal sulcus it is probably in an ectopic position. • Position confirmed radiographically using two intraoral views with different tube positions. The tooth furthest from the tube moves in the same direction as the tube according to the parallax principle. It does not deal with the canine that is high. Use a DPT and standard occlusal radiograph using parallax principle. Treatment:- i. Remove the deciduous canine. This will help to bring the permanent canine back to a normal course of eruption. ii. Note whether there is any root resorption of either the lateral or central incisor. Maybe well advanced by 12 yrs but rarely starts after 14 yrs. The affected incisor(s) may be symptomless and remain vital and firm even with only half a root. Treatment where the canine is not markedly displaced i. Insufficient space for the canine, either distalize the buccal segments or extract the upper first premolar. If the canine is in the line of the arch no appliance treatment may be necessary. Treatment Options For Displaced Canines: Is the patient prepared to accept treatment which will be prolonged. 1) Leave, review radiographically to see if crypt enlarges with cystic formation. 2) Extract especially if deciduous canine crown and root are good or if the first premolar contacts the lateral incisor. 3) If the deciduous canine needs to be extracted then an extra 2 mm of space will be needed to accommodate the permanent canine. Either by approximating spaced anterior teeth or distalizing buccal teeth. Treatment Of Established Palatal Canine 1) Provide adequate space as in 3) above or extract a premolar in crowded cases. In some cases the canine tooth will erupt. 2) In most cases surgical exposure is needed with or without attachment of a gold chain so an appliance can be used to align the tooth. 3) Surgical transplantation:- canine is surgically accessible and there is sufficient space within the arch. Splinting for 2-3 weeks to allow formation of a normal periodontal attachment. Vitality of the transplanted canine is less important in the assessment of success than viability. If the tooth is firm with no radiological signs of apical rarefaction or root resoption then endodontic treatment should not be instituted for the tooth that shows no response to vitality testing. After 2 yrs a degree of root resorption is present in 50% of cases. Teeth with patent apices achieve a new pulpal blood supply more readily and have a higher chance of success. ABNORMAL POSITION OF CRYPTS The crypt of any tooth may be displaced or rotated. Lower second premolar can show tipping of its developing crown which usually corrects in later development. The third molar shows a wide range of crown orientation which may improve during development. There is little that early intervention can do except in the case of the developing maxillary canine. Appendix Page 6
  29. 29. PREMATURE LOSS OF DECIDUOUS TEETH Balancing extraction is the removal of the contralateral tooth. Compensating extraction is the removal of the equivalent opposing tooth. The major effect of early loss of a primary tooth is localisation of pre-existing crowding although this will not occur in uncrowded cases. Where there is crowding the adjacent teeth will drift/tilt into the extraction site. This will depend on the site, degree of crowding and age of the patient. There is a greater tendency for mesial drift in the maxilla; the younger the patient is; and the more crowded dentitions. With regard to the site consider tooth types: Deciduous incisor: little impact as shed early. Deciduous canine: in a crowded mouth there will be a centre line shift to the affected side. Should be balanced even in mild crowding cases. Deciduous first molar: may result in centre line shift. Kept under review and balanced if necessary. The second deciduous molar and first permanent molar drift forwards without rotation or tilting and the anterior teeth spread around the arch. In the upper arch the first premolar usually erupts into the arch but the canine is outlocked. In the lower arch the effect is more variable and sometimes the canine erupts first and the first premolar is short of space. Deciduous second molar: if the second deciduous molar is extracted before eruption of the first permanent molar, the latter tooth will erupt in a more anterior position and total space loss may occur. With later extraction, the upper first permanent molar tips mesially with some rotation. The upper second premolar usually erupts into the palate and the lower erupts lingually or with later extraction may impact vertically between the lower first molar and first premolar. Should try and preserve second deciduous molars until the permanent tooth has erupted. In most cases balancing or compensating extractions of other sound second deciduous molars is not required. Space maintenance and balancing or compensating extractions Many children have potentially crowded arches and will require extraction of permanent teeth so the use of space maintainers is rarely essential. Space maintenance may be advantageous where there is acceptable alignment of teeth but with a tendency to mild crowding. In such a case, early loss may produce a localised malocclusion for which it is difficult to plan simple treatment. • Disadvantages of space maintenance 1) May need prolonged wear and there is no guarantee that this will avoid the need for later orthodontic treatment. 2) May hinder plaque control and precipitate an increase in caries. 3) Removable space maintainers fail if not worn and fixed ones need regular inspection. • The natural tooth forms the ideal space maintainer and attempts should be made to conserve the single carious deciduous molar by pulp treatment if required. • Where extractions have to be carried out under GA, balancing and compensating extractions should be considered. Where contralateral and opposing teeth are of poor prognosis there is no difficulty in applying the principles of balancing and compensating extractions. Balancing extractions are designed to eliminate centre line discrepancies that will require fixed appliances for their correction. Compensating extractions are a means of preserving interarch relationships by allowing the posterior teeth to drift forward ! General rules for balancing and compensating extractions In CL I cases with mild crowding: if a first deciduous molar has to be extracted on one side in the upper arch the contralateral tooth should be extracted to preserve the centre line and allow some temporary improvement in incisor crowding. This is a balancing extraction. If one deciduous molar has to be extracted in the lower arch it may be desirable to balance this with the contralateral tooth. This may signal the need for compensating extractions in the upper arch particularly if the teeth are of poor quality. In CL II cases with crowding and a deep overbite treatment will be required later. In the lower arch should not balance or compensate the loss of a deciduous molar. The reverse is true in the upper arch. It used to be thought that loss of second deciduous molars should not be balanced or compensated because the effect on the centre line was minimal. Recent evidence suggests that centre line shifts occur when these teeth are removed prior to the eruption of crowded permanent incisors. ! THE UPPER LABIAL FRAENUM This occasionally modifies the position of the teeth. In infancy the labial fraenum is frequently attached to the crest of the alveolar ridge in the midline between the upper central incisors. With normal dento-alveolar growth, the upper alveolar process grows down and the frenal attachment becomes higher with no influence on tooth position. Occasionally the low attachment persists and the fraenum causes a midline space ‘median diastema’ between the central incisors. Factors which may indicate that this is the case include:-the anterior teeth may be crowded; radiographically a notch can be seen at the crest of the interdental bone between the upper central incisors and when the fraenum is placed under tension there is blanching of the incisive papilla. Management Wait until the permanent canines erupt to see if the space closes. If not resect the fraenum (frenectomy) and institute appliance treatment to close the space. ! There are other causes of median diastema. • Median diastema: prevalence 98% of 6 yr-olds, 49% of 11 yr-olds and 7% of 12-18 yr-olds. • Aetiology: physiological (normal dental development). • Hypodontia, especially missing upper lateral incisors. • Small teeth in large jaws (spaced dentition). • Presence of midline supernumerary tooth/teeth. • Proclined upper incisors. Management Periapical radiograph to exclude the presence of supernumeraries. If the diastema is larger than 3 mm and the lateral incisors are present it may be necessary to approximate the central incisors to provide space for the canines to erupt. Care should be taken to ensure that the roots of the teeth being moved are not pressed against any unerupted crowns as this can lead to root resorption. Diastemas have a high tendency to relapse following closure so permanent retention will be required. INDICATIONS FOR THE EXTRACTION OF DECIDUOUS CANINES • In a crowded upper arch the lateral incisors may be forced palatally. In a CL I case this will result in a crossbite and the apex of the tooth will be forced palatally making correction difficult. • In a crowded lower arch one incisor may be forced through the labial plate of bone, resulting in a dehiscence, compromising the periodontal attachment. Relief of crowding by extracting the lower deciduous canines usually resolves the situation. • Extraction of lower deciduous canines can be advantageous in CL III cases. • To provide space for appliance therapy in the upper arch, for example correction of an instanding lateral incisor or to facilitate the eruption of an incisor prevented from erupting by a supernumerary tooth. • To improve the position of a displaced permanent canine. Appendix Page 7