Functional & ceph analysis for functional appliance /certified fixed orthodontic courses by Indian dental academy


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Functional & ceph analysis for functional appliance /certified fixed orthodontic courses by Indian dental academy

  2. 2. Introduction • • • • • Functional examination is of special significance in treatment of functional appliances because of dynamic basis of therapy, An initial functional assessment is imperative Function is ,indeed, the common denominator that joins the individual parts of the orofacial system into a dynamic,integrated and purposive system Disturbance in one part of the orofacial system do not remain isolated but affect the equilibrium of the whole system This unique quality is of importance in etiological considerations and when assessing the effectiveness and various side effects of different orthodontic appliance
  3. 3. Proper treatment plan and prognosis depends on accurate diagnosis.Any abnormal function which is detected should be corrected for favourable treatment outcome. Three most important aspects of orthodontic functional analysis are: 1.Examination of postural rest position and maximum intercuspation 2.Examination of the TMJ 3.Examination of orofacial dysfunction
  4. 4. Examination of the relationship : Postural rest position – Habitual occlusion    Determination of the postural rest position Registration of postural rest position Evaluation of the relationship: Postural rest position – Habitual occlusion in 3 planes of space The rest position should be determined with the patient relaxed and sitting upright.The head is oriented by having the patient look straight ahead (habitual position). If this seems too variable, then the head can be positioned with the frankfurt horizontal parallel to the floor.
  5. 5. Determination of postural rest position    Patient’s orofacial musculature must be relaxed Muscle exercises to relax the musculature – “ TAPPING TEST” If patient is tensed – mild electric impulses to relax the musculature When the mandible is in the postural resting position,it is usually 2-3mm below and behind the centric occlusion,recorded in canine area
  6. 6. Methods used to determine the rest position during clinical examination      Phonetic method Command method Non-command method Combined method Phonetic method: Patient is told to pronounce certain consonants or words repeatedly (e.g.”M”,”Mississippi”).The mandible returns to the postural resting position 1-2 seconds after the exercise  Command method: The patient is “commanded” to perform selected functions(e.g.Swallowing),after which the mandible spontaneously returns to the rest position
  7. 7. Non-command method: The patient is distracted,so as not to percieve which type of examination is carried out.while being distracted, the patient relaxes,causing the musculature to relax as well,and the mandible reverts to the postural rest position Combined method: Most suitable for functional analysis in children.the patient is first observed during swallowing and speaking.Older children – tapping test ,then non- command method • Regardless of the clinical method in use, the mandible must be checked extraorally to ensure that it actually has assumed the rest positionpalpate the submental region :relaxed muscles in this area indicate that the rest position has been attained. • The lips are then carefully parted with the thumb and forefinger – to observe the maxillomandibular relationship
  8. 8. Registration of the rest position Two most commonly used methods  Intra oral indirect method (using impression materials)  Extra oral direct method (using skin reference points) Extra oral indirect methods are the most reliable • Roentgenocephalometric registration • Kinesiographic registration
  9. 9. Roentgenocephalometric registration Two cephalograms are required, either in lateral or frontal projection,  One radiograph in centric(habitual)occlusion  One with mandible in its rest position • The rest position and freeway space can be determined by comparing the radiographs
  10. 10. Kinesiographic registration Mandibular kinesiograph,according to Jankelson, allows the mandibular rest position to be registered 3-D.The position of mandible is recorded electronically by:  A permanent magnet, which is fixed with rapid setting acrylic to the lower anterior teeth  A sensor system of six magnetometers mounted on spectacle frames Every movement of the mandible and the attached magnet out of centric occlusion, alters the strength of the magnetic field.These changes are recorded by the sensors , processed in the kinesiograph and displayed on a storage oscilloscope The Mandibular movements and rest position are recorded twodimensionally on two preselectable levels.The electronic circuitary also allows the rest position to be recorded as 3-D co-ordinates
  11. 11. Evaluation of the relationship between rest position and habitual occlusion The movement of the mandible from the rest position to full articulation is analysed three dimensionally:sagittal , vertical and frontal planes The closing movements of the mandible can be divided into two phases  Free phase:mandibular path from the postural rest to the initial or premature contact position  Articular phase:mandibular path from the initial contact position to centric or habitual occlusion.
  12. 12. When closing from the rest position, the mandible may undergo both rotational and sliding movements.The objective of this analysis is to determine the amount and direction of movement as well as the proportions of the rotational and sliding components. The following movements of the mandible from the rest position to habitual occlusion must be differentiated for orthodontic diagnosis:  Pure rotational movement (hinge movement)  Rotational movement with an anterior sliding component  Rotational movement with a posterior component
  13. 13. Evaluation in the sagittal plane When evaluating the relationship of the rest position to habitual occlusion in the sagittal plane,the exceptional features of the class II and class III malocclusions are analysed Class II malocclusion According to different types of movement of the mandible from the rest position to occlusion, the classII malocclusion can be divided into 3 types  Rotational movement without a sliding component-the neuromuscular and morphologic relationships correspond to each other.There is no functional disturbance (functional true classII)
  14. 14.  Rotational movement with posterior sliding movement The mandible slides backwards and is guided into a posterior occlusal position.This finding reveals a functional class II malocclusion and not a true class II malrelationship  Rotational movement with anterior sliding movement starting from the relatively posterior rest position The mandible slides forwards into habitual occlusion.The class II malocclusion is actually more pronounced than can be seen in habitual occlusion
  15. 15. • • • • • Treatment prognosis for functional appliance therapy is dependent on the analysis of the relationships and the determination of the path of closure category In functional class II malocclusions,the elimination of the functional retrusion or protrusion leads to an improvement of the sagittal relationship In class II malocclusions with a normal path of closure,the intermaxillary relationship must be altered,but this requires both a morphological and a functional change to produce the desired sagittal correction In case of posterior displacement,combined with a projected horizontal growth direction,the prognosis for class II treatment is very good When there is an anterior displacement and a vertical growth vector,the prognosis is poor
  16. 16. Class III Malocclusions The functional relationships of class III cases determine the orthodontic treatment possibilities and the prognosis of malocclusion. The closing path of the mandible from the rest position can be divided into three types  Rotational movement without sliding action The anatomic/morphologic relationships correspond to the functional relationship (non – functional,true class III malocclusion – unfavourable prognosis)
  17. 17. Rotational movement with anterior sliding action. During the articular phase, the mandible shifts forwards and into a prognathic, forced bite(functional , non skeletal malocclusion , so called pseudo class III – favourable prognosis)  Rotational movement with posterior sliding action. In case with pronounced mandibular prognathism,the mandible may slide posteriorly into the position of maximum intercuspation.This masks the true sagittal dysplasia
  18. 18. True forced bite – pseudo –forced bite • In case of mesio occlusion an anterior sliding action is not always a symptom of a functional class III malocclusion. • With this functional diagnosis, the “true forced bite”,with its favourable prognosis, and the “pseudo forced bite”, with its unfavourable prognosis ,must be differentiated as far as cephalometrics is concerned. • The term “pseudo-forced bite” includes those true skeletal class III malocclusions where, due to partial dentoalveolar compensation of the skeletal dysplasia in the anterior region,the mandible occludes at the end of the closing path by means of an anterior sliding action.If one reconstructs the tipping of the anterior teeth in a pseudo-forced bite,these cases have a pronounced negative overjet • The dentoalveolar compensation of the skeletal dysplasia,which already exists when treatment is started ,greatly restricts the range of orthodontic treatment possibilities and unlike a true forced bite, is indicative of a very unfavourable prognosis
  19. 19. Evaluation of the relationship between rest position and habitual occlusion in a vertical plane • • • The vertical dimension of free way space is assessed.This analysis is of particular importance to cases with a deep over bite The true deep overbites with a large freeway space,is caused by infraocclusion of molars.the prognosis for successful therapy with functional methods is favourable.As the interocclusal cleerance is large, sufficient freeway space will remain after extrusion of molars The pseudo – deep overbite has a small freeway space.The molars have erupted fully.The deep overbite is caused by over eruption of the incisors.The prognosis for elevating the bite using functional appliances is unfavourable if the freeway space is small, extrusion of molars adversely affects the rest position and may create TMJ problems or cause a relapse of the deep overbite
  20. 20. Evaluation of the relationship between rest position and habitual occlusion in the transverse plane The position of midline of the mandible is observed while the jaw is moved from the postural rest to habitual occlusion.This analysis is particularly relevant for the differential diagnosis of cases with unilateral cross bite. Depending on the functional analysis two types of skeletal mandibular deviation can be differentiated: laterognathy and laterocclusion Laterognathy: The centre of the mandible is not aligned with the facial midline in rest and occlusion.These dysplasia constitute true neuromuscular or anatomical assymetry. A lateral cross bite with laterognathy is termed true cross bite.The prognosis is unfavourable for causal therapy Laterocclusion:The skeletal midline shift of the mandible can be observed only in occlusal position;in postural rest both midlines are well aligned.The deviation is due to tooth guidance(functional non-true malocclusion)
  21. 21. Examination of the temperomandibular joint • • Through the early elimination of functional disturbances,some incipient TMJ problems can be prevented or eliminated,this is an indication for early orthodontic treatment. During activator therapy the condyle is diclocated to achieve a remodelling of the TMJ structures and a change in muscle function.If temperomandibular structures are abnormal at the start and hypersensitivity is a problem,the possibility of exacerbating the symptoms exists
  22. 22. Clinical examination Main objective – assess the severity of the clicking, pain and dysfunction,which are characteristics of pathologic TMJ symptoms.  When auscultation is carried out with the stethescope,clicking and crepitus in the joint may be diagnosed during A-P and eccentric movements of the mandible. Joint clicking is differentiated as follows: initial,intermediate,terminal and reciprocal clicking Initial clicking : retruded condyle in relation to the disc Intermediate clicking : unevenness of the condylar surfaces and of the articular disc, which slide over one another during the movements Terminal clicking : condyle being moved too far anteriorly, in relation to the disc,on maximum jaw opening Reciprocal clicking : incoordination between displacement of the condyle and the disc,during opening and closing
  23. 23.  Palpation of the TMJ during opening maneuvers - possible pain on pressure of the condylar area Besides the right and left condyles can thus be checked of synchrony of action. Palpation of the musculature involved in the mandibular movements is a considerable part of examination. In cases with functional disturbances during childhood only LATERAL PTERYGOID causes pain due to pressure. MASSETER muscle pain is also encountered in children with TMJ problems.therefore, these muscle attachments should be examined on every orthodontic patient . Initial symptom of TMJ disturbance – palpatory tenderness of muscles Temporalis and masseter muscles are palpated during unconsious swallowing b’cos this could be different from swallow on command (AO 1987) .  • •
  24. 24. Opening and closing movements of the mandible   Size and direction of opening and closing are recorded during the clinical examination Deviations in speed can only be registered with electronic device(eg.kinesiograph) First signs of initial TMJ problems include deviations of the mandibular opening and closing path in the sagittal and frontal planes.In patients with malocclusion and malaligned teeth,disturbances in mandibular movements are the result of an asynchronic pattern of muscle contractions.the characteristic movement deviations include incongruency of the opening and closing curves and uncoordinated zigzag movements.the “C” and “S” types of deviation are typical signs of funcrional disturbances. Occlusal analysis – in patients with symptoms of TMJ disease
  25. 25.
  26. 26. TMJ – Radiographic examination • • • PA projections according to Ciementschitsch, Radiographs according to schuller or Parma,Tomograms – suitable for examination of the TMJ Following findings registered : Position of condyle in relation to fossa Width of the joint space Changes in shape and structure of the condylar head / mandibular fossa
  27. 27. Examination of orofacial dysfunction      Swallowing Tongue Speech Lips Respiration
  28. 28. Swallowing   Normal mature swallowing – without contracting the muscles of facial expression.Teeth are momentarily in contact and the tongue remains inside the mouth Abnormal swallowing – caused by tongue thrust 1. 2. 3.   Protrusion of the tip of the tongue No tooth contact of the molars Contraction of the peri-oral muscles during the deglutition cycle First few years – infants swallow viscerally, with tongue between the teeth;As the deciduous dentition is completed , visceral swallowing is replaced is replaced by somatic swallowing If visceral swallowing persist after 4 yrs of age – Orofacial dysfunction
  29. 29. Examination of the tongue  Tongue function: • The object of tongue function assessment is to make differential diagnosis possible and determine tongue’s role in malocclusion Functional appliance therapy is indicated if the role of the tongue malfunction is a primary etiological factor A correction of basal dysplasia of skeletal parts – establishment of normal tongue function • •  Tongue posture: • Root is flat in mouth breathing and deep overbite caused by a small tongue In class II div I and deep over bite,dorsum of the tongue – arched and high;tip of the tongue – retracted •
  30. 30. Cephalometric evaluation of tongue posture • • Lateral cephalogram taken in postural rest and habitual occlusion Changes in tongue position relate to different types of malocclusionclass II – tip of the tongue is more retruded in rest position class III – tongue lies forward in rest position
  31. 31. Tongue thrust Important effect on etiopathogenesis of malocclusions 1.Anterior tongue thrust – dysfunction during development of anterior open bite 2.Lateral tongue thrust – dysfunction during development of lateral open bite 3.Complex tongue thrust – occlusion supported only in the molar region • • • • • The dentoalveolar anterior and posterior open bite problems - attributable to abnormal tongue posture and function – responds successfully to functional appliance intervention in mixed dentition This is also true in cases of deep overbite,in which lateral tongue spread during posture and function has resulted in infraocclusion of posterior teeth A second type of over bite – caused by supraocclusion of the incisors – small free way space,this type of problem is called functional pseudo overbite,in these cases functional appliance is not indicated In skeletal open bite problems,there is a genetically determined vertical growth pattern,often associated with marked antegonial notch – does not offer a favourable prognosis for orthodontic therapy
  32. 32. • The consequence of tongue posture and function abnormalities in the dentoalveolar region also depends on skeletal pattern - In horizontal growth pattern , forward tongue thrust – bimaxillary protrusion - In vertical growth pattern, the tongue thrust can open the bite,lower incisors may be tipped lingually
  33. 33. Palatographic examination of the tongue • • • • • Enables observation of tongue function during swallowing and speaking ,evaluation of the influence of various functional orthodontic appliances on the tongue Direct method – by Oakley,gum arabic and flour mixed and painted on the tongue,after going through the selected functional exercises,the contacts on the palate and teeth were transferred onto the casts Indirect method – by Kingsley,blsck rubber placed on the palate and tongue covered with mixture of chalk and alcohol Current direct method – superior surface of tongue covered with precise impression material;after functional exercises a polaroid print is made of the palatal region with a surface mirror,the evaluation of the palatogram is by direct measurements on the picture Tongue with its inherent flexibility can compensate for atypical morphological relationship,this compensatory potential as assessed by palatographic record is an important diagnostic clue to establish a treatment plan and a probable prognosis for functional appliance therapy
  34. 34. Configuration of the craniofacial skeleton and dysfunctions  Horizontal growth pattern with tongue thrust – bimaxillary dental protrusion Vertical growth pattern with tongue thrust – lower incisors in lingual inclination 
  35. 35. Methods of examination • • • • • • • Electronic recordings Electromyographic examination Recording pressure exerted by tongue intraorally Roentgenocephalometric analysis – assess position and size of the tongue Cine radiographic examination Palatographic examination – records the contact surfaces of the tongue with palate and teeth Neurophysiologic examination
  36. 36. Lip dysfunctions Assessed in relation to configuration and functioning of the lips Configuration of the lips • Competent lips : lips in slight contact when musculature is relaxed • Incompetent lips : Anatomically short lips , do not touch when musculature is relaxed.lip seal is achieved by active contraction of the Orbicularis oris and the Mentalis muscles • Potentially incompetent lips :The protruding upper incisors prevent the lip closure.otherwise the lips are developed normally • Everted lips : these are hypertrophied lips with redundant tissue but weak muscular tonocity 
  37. 37. Various methods are available for evaluating the lip profile  Schwarz analysis H line – corresponding to frankfort horizontal Pn line – perpendicular to the H line at soft tissue nasion Po line – perpendicular from orbitale to the H line Between the two construted perpendicular lines is the Gnathic profile field ( GPF)
  38. 38.  Ricketts lip analysis • Reference line similar to the Schwarz T line,but is drawn from the tip of the nose to soft tissue pogonion Normally,upper lip is 2-3mm and lower lip is 1-2mm behind this line •  Steiner lip analysis • Upper reference point – center of the Sshaped curve between the tip of the nose and subnasale,lower terminus – soft tissue pogonion If lip lie behind this line – they are too flat ; if they lie in front – they are too prominent •
  39. 39.  Holdaway lip analysis • Quantitative assessment of lip configuration H angle – angle between the tangent to the upper lip from soft tissue pogonion and the NB line Ideal profile A-N-B angle - 2 degrees H angle – 7-8 degrees Lower lip touching the soft tissue line that connects pogonion and the upper lip extended to S-N Relative proportions of nose and upper lip balanced Tip of the nose 9mm anterior to the soft tissue • • line
  40. 40. Lip habits Lip-sucking • Lip-thrust • Lip insufficiency Any lip activity during swallowing – apart from closing the lips – is unphysiologic and a symptom of an orofacial dysfunction.visual evidence of mentalis muscle activity is also abnormal • Cheek dysfunctions In cheek – sucking or cheek – biting the soft tissues are interposed between the occlusal surfaces of the teeth – formation of lateral open bite. • Increased lateral pressure by cheek musculature on the mandible impedes the transverse development of the jaw • Common in cases with buccal nonocclusion •
  41. 41. Hyperactivity of Mentalis muscle •Characteristic feature – deep mentolabial sulcus •Impedes forward development of the anterior alveolar process in the mandible Mouth-Breathing • • Chronically disturbed nasal respiration – restrict development of the dentition and hinders the orthodontic treatment Clinical findings: o o o o o o High palate Persisting “tooth germ position” of the upper incisors Narrowness of the upper arch Cross bite Hyperplasia of the gingiva Extra oral appearance – “adenoid facies”
  42. 42. Pattern of facial morphology • • The configuration of facial skeleton and oral respiration are correlated Proliferation of the adenoids , incidence of hypertrophied tonsils – pronounced in patients with oronasal respiration NO ADENOIDS SMALL ADENOIDS LARGE ADENOIDS
  43. 43. Examination of breathing mode •The cotton pledget test •The mirror test •Observation of the nostrils The scope of functional therapy in patients with respiratory problems 1.In habitual mouth breathing with small respiratory resistance, a functional therapy is indicated.exercises can be prescribed,holding a sheet of cardboard between the lips is a good means of enhancing the lip seal 2.When there are structural problems,with excessive adenoid tissue , allergies,orthodontics can be carried out after successful ENT treatment 3.If the structural conditions cannot be altered,functional appliance therapy cannot be instituted,in such cases , only active fixed appliance mechanotharapy is likely to produce the change desired
  44. 44. The significance of functional analysis in treatment planning with removable appliances : • • • • Mandibular over closure and deep overbite with large free way space – prognosis for treatment with functional appliance is good A true skeletal class III malocclusion does not offer a favourable prognosis for functional appliance Functional appliance therapy is particularly indicated in pseudo class III malocclusions with normal tongue posture Functional appliance therapy is likely to be successful in cases with primary dysfunction in open bite and an average growth pattern
  46. 46. The following information can be ascertained from the cephalometric analysis • • • • • • • Configuration of the facial skeleton Relationship of the jaw bases Relationship of the axial inclination of incisors Assessment of the soft tissue morphology Growth pattern and direction Localisation of the malocclusion Treatment possibilities and limitations
  47. 47. Cephalometric reference points • • • Reference points- located in the skeletal,dentoalveolar and soft tissue regions Include anatomic , radiographic and constructed points Constructed point not accurate – methodological error of individual point localisation accumulates
  48. 48.
  49. 49. Cephalometric reference lines
  50. 50. Aims of interpretation of cephalometric measurements: • • • • • Analysis of skeletal structure and facial type Assessment of vertical and sagittal relationship between maxillary and mandibular bases Differentiation of skeletal and dentoalveolar malocclusions Analysis of dental relationships Analysis of soft tissue regarding etiology and prognosis
  51. 51.  The cephalometric critria can be divided into three groups • 1.Analysis of facial skeleton 2.Analysis of jaw bases 3.Analysis of the dentoalveolar relationship • • 1.Analysis of facial skeleton -Three angular measurements – saddle angle ,gonial angle and articular angle -four linear measurements – anterior and posterior facial height,anterior and posterior cranial base length
  52. 52.  The saddle angle ( N-S-Ar) • The angle that is formed by joining the points N , S and Ar is an assessment of the relationship between anterior and posterolateral cranial bases Large saddle angle – posterior condylar position ,and mandible that is posteriorly positioned with respect to the cranial base and the maxilla A non compensated posterior positioning of the mandible , caused by a large saddle angle , is very difficult to influence with functional appliance theraphy The articular angle (S–Ar-Go) Constructed angle that lies between the upper and lower parts of the posterior contours of the facial skeleton.the size of this angle depends upon the position of the mandible It is large when mandible is retrognathic and small when mandible is prognathic The angle can be influenced during orthopedic theraphy,it increases with posterior relocation of the mandible , with opening of the bite,and decreases with anterior positioning of the mandible,with closing the bite • •  • • •
  53. 53.  • • •  • • • • The Gonial angle (Ar-Go-Me) The angle formed by tangents to the body of the mandible and posterior body of the ramus – expresses the form of the mandible and information on its growth direction If this angle is acute or small , the direction of growth is horizontal.This is a favourable condition for anterior positioning of the mandible with an activator In cases with a large angle,activator treatment is contraindicated , or appliance must be constructed taking into account the growth pattern Facial height The posterior facial height (S-Go) and the anterior facial height (N-Me) are measured on the lateral cephalogram with the teeth in habitual occlusion To estimate the direction of growth that is so important in activator treatment, we can compare anterior and posterior facial height and set up a ratio, according to the recommendations of Jarabak, posterior facial height * 100 / anterior facial height A ratio of less than 62 % expresses a vertical growth pattern,ratio of more than 65 % - horizontal vector The growth forecast for early mixed dentition treatment with an activator should be carried out by comparing angular and linear measurements and morphological characteristics of the mandible
  54. 54.  Anterior cranial base length (Se – N ) • This measurement is made using the centre of the superior entrance to the sella turcica as a reference point , instead of sella turcica fossa outline that is usually used for cranial base establishment The correlation of this criterion to the length of the jaw bases enables an assessment of the proportional averages of these bases Average length of the anterior cranial base – 68.8mm for horizontal growth patterns , 63.8mm – vertical growth vector • •  Posterior cranial base length (S – Ar) • Short posterior cranial base – vertical growth pattern or a skeletal open bite – poor prognosis for functional appliance therapy
  55. 55. 2.Analysis of the jaw bases The angles between the vertical reference lines represent the sagittal relationship (the SNA angle and the SNB angle).The angles between the horizontal lines assist in evaluating the vertical ralationship of parts (base plane angle and inclination angle).the linear measurements give an indication of the length of the maxillary and mandibular bases as well as the length of the ascending ramus  SNA angle • Expresses the sagittal relationship of the anterior limit of the maxillary apical base ( point A ) as related to the anterior cranial base This angle is large in a prognathic maxilla and is small in a retruded maxilla When a prognathic maxilla causes class II,division I malocclusions and there is a larger than normal SNA angle, the use of activator is contraindicated • •
  56. 56.  • • • • •  • • SNB angle Expresses the sagittal relationship of the anterior apical base of the mandibular arch and the anterior cranial base Prognathic mandible – angle is large , retrognathic mandible – angle is small Functional appliance treatment is indicated if the mandible is retrognathic with a small SNB angular reading A posteriorly located mandible can be large or small,if it is small the prognosis for anterior posturing in the mixed dentition is good,since a larger growth increment can usually be expected Together with the favourable growth direction, the greater growth increments on the mandible in the horizontal pattern enables successful treatment of these cases by anterior posturing of the mandible in functional appliance therapy Basal plane angle ( Pal – MP ) Expresses the angle between the maxillary and mandibular jaw bases and used to determine the inclination of mandibular plane itself In the horizontal growth pattern this angle is small, whereas it is large in vertical growth group
  57. 57.  Inclination angle • Gives an assessment of the inclination of the maxillary base It is the angle formed by the Pn line and the palatal plane A large angle expresses upward and forward inclination, whereas a small angle indicates a downward and backward tipping of the anterior end of the palatal plane or maxillary base • •
  58. 58.  Rotation of the jaw bases Basal plane angle and inclination angle are used to evaluate the rotation of the upper and lower jaw bases • These rotations are of special interest in treatment with functional appliances because they show whether such appliances are indicated and provide criteria for appliance construction Bjork differentiates the two processes involved in the rotational growth of the mandible 1.remodelling of the mandible in the symphyseal and Gonial areas – intermatrix rotation. Apposition in the gonial area, resorption in the symphyseal area- horizontal rotation Apposition in the symphyseal area , resorption in the gonial area – vertical rotation 2.vertical or horizontal rotation of the mandible in its neuromuscular envelope – matrix rotation. rotation observed cephalometrically is called total rotation,it consists of both intermatrix and matrix rotation • Functional orthodontic and orthopedic methods alter the function and guide the growth process,rotation of the mandible may be moderately influenced therapeutically •
  59. 59. Rotation of the Maxillary base The Inclination angle records the rotation of the maxillary base to the anterior cranial base • The angle is not measured directly,but defined as the angle between the Pn-perpendicular and the palatal plane • Anteinclination-forward maxillary rotation retroinclination-backward maxillary rotation • Maxillary inclination influences the clinical appearance of the anterior tooth position,it can be changed by dentofacial orthopedic treatment. NORMALINCLINATION = 85 ANTELNCLINATION > 85 RETROINCLINATION < 85 • Combinations of maxillary and mandibular rotation •Convergent rotation of the jaw bases •Divergent rotation of the jaw bases •Upward rotation of both jaw bases •Downward rotation of both jaw bases
  60. 60. Rotation of the jaw bases Convergent and Divergent rotation •Combination of the maxillary and mandibular rotation determines the degree of the anterior overbite •When the jaw bases are rotated equivalently in the same direction,the vertical dimension during growth remains constant •Convergent rotation – deep bite Rotation in the same direction • Divergent rotation – open bite
  61. 61. Linear measurement of the jaw bases • • •  • • In the determination of indication for functional appliance therapy,both the position and the length of the jaw bases must be assessed The length of the maxillary and mandibular bases and ascending ramus is measured relative to Se-N The ideal dimension relative to Se-N is calculated using the following ratios N-Se : Man base - 20 : 21 Ascending ramus : Man base – 5: 7 Max base : Man base – 2 : 3 Extent of the mandibular base Determined by measuring the distance Gonion – Pogonion Ideally the mandibular base should be 3mm longer than Se-N
  62. 62.  Extent of the maxillary base • Distance between the posterior nasal spine and point A projected perpendicularly onto the palatal plane The evaluation of this dimension has two “ideal” measurements : one related to N-Se and the other to the length of the mandibular base •  Length of the ascending ramus • Distance between Gonion and Condylion Important in determination of posterior facial height and subsequent relation to the anterior facial height •
  63. 63. Evaluation of the length of the jaw base  • • • • • Mandibular base If the length of the mandibular base corresponds to the distance N-Se,it indicates an age related normal mandibular length and an average growth increment can be expected If the base is shorter,growth increment is larger;if the base is longer,growth increment is smaller A retrognathic mandible may have either short or long base If base is short the cause of retrognathism is a growth deficiency;if a favourable growth direction is present ,the prognosis for functional appliance therapy is good A mandibular base that is both long and retrognathic can result from two possibilities 1.The mandible is in a functionally retruded position because of over closure and occlusal postural rest,it is anterior to habitual occlusion.treatment is simple – elimination of the forced guidance and up and back path of closure in either the mixed or permanent dentition 2.The mandible is morphogenetically “built” into the facial skeleton in a posterior position.the temporal fossa is posterior and superior.This discrepancy is not compensated despite the long mandibular base.the prognosis for functional appliance therapy in these cases is poor
  64. 64.  Maxillary base • Assessment of length of maxillary base has 2 ideal values : one related to the distance N-Se,the other to the length of the mandibular base A deviation from the mandibular base-related norm --- maxillary base is too long or too short If the maxillary base corresponds to the mandibular base - related norm,the facial skeleton is proportionally developed,particularly if the ramal length also corresponds to these values If the N-Se length does not relate to these three proportionate measurements,the facial skeleton is proportionate but either too large or too small • • •  Ascending ramus • If the ramus is too short in relation to the other proportions,a large amount of growth can be expected because the growth pattern is not vertical In vertical growth patterns the ramus remains short •
  65. 65.  Morphology of the mandible • Orthognathic type of face – ramus and body of the mandible are fully developed,width of the ascending ramus is equal to the height of the body of the mandible,including the height of the alveolar process and incisors.the condylar and coronoid processes almost on the same plane,and the symphysis is well developed In the prognathic type the corpus is well developed and wide in the molar region.The symphysis is wider in the sagittal plane.the ramus is wide and long ,and gonial angle is acute or small Retrognathic facial type the corpus is narrow,particularly in the molar region.the symphysis is narrow and short,coronoid process is shorter than the condylar process,and the gonial angle is obtuse or large The prognathic type of mandible grows horizontally.even if an average or slightly vertical growth direction is evident in the mixed dentition,shifting of the mandible to a horizontal growth direction can be expectd in the following years In a retrognathic mandible,shifting of the growth pattern in the opposite direction is less likely and produces much less expressivity • • • •
  66. 66. •Analysis of dentoalveolar relationship   Axial inclination of incisors Position of the incisors  Axial inclination of the incisors  Upper incisors • The long axis of the maxillary incisors is extended to intersect the S-N line,and the posterior angle is measured Larger angles indicate a procumbency or labial crown tipping Incisor protrusion requires lingual tipping,a therapeutic objective that can be achieved with removable appliances if adequate space is available • •
  67. 67.  Lower incisors • To assess axial inclination of the teeth – measurement of the posterior angle between the long axis of the lower incisors and the mandibular plane Ideal angle – 90 degrees Smaller angle – lingual tipping of the incisors – advantages for functional appliance treatment Classical activators are most effective in the sagittal plane and tend to tip the lower incisors labially If lower incisors are already labially tipped , functional appliance treatment is more difficult;anterior repositioning of the mandible and uprighting of the lower incisors become necessary,if possible moved in the opposite direction This requires special appliance design in the lower anterior segment • • • • •
  68. 68.  Position of the incisors • Linear measurements are the best assessors of the position of the incisors with respect to the profile Common method – to measure the distance of the incisal edges to the N-Pog line – Facial line Average position of the maxillary incisors is 2 to 4 mm anterior to the N-Pog line.the lower incisors vary from 2mm posterior to 2mm anterior to this line The relationship of the lower incisors to the NPog line also helps determine the sagittal discrepancy Incisors behind this line can be moved labially because space is available,incisors anterior to the facial plane that must be moved lingually require additional space,which may be obtained only by extraction procedures The amount and direction of growth spurt should be considered in the mixed dentition,while ideal position of incisors is being planned • • • • •
  69. 69. Anteroposterior skeletal assessment o The AP position of the jaws is assessed based on measurements that use the true horizontal (TH) as the reference line  Size of the mandible (Go-Gn) relative to the anterior cranial base (SNa) • A ratio of GoGn:SN=1 indicates a well balanced mandibular body relative to the cranial base. The importance of this measurement lies in the fact that a very retrognathic profile may be due to a short mandibular body that affects the anteroposterior plane , which may require surgical intervention, depending on the deformity and age of the patient •  Maxillomandibular ratio (PNS-ANS:ArGn) • According to Michigan growth atlas, the length of the mandible,defined from Articulare(Ar) to Gnathion(Gn), is almost exactly double of the maxillary length,defined from posterior and anterior nasal spine(PNS-ANS) A ratio of 1:2 indicates the actual lengths of the maxilla and mandible are in good balance with each other. •
  70. 70.  Assessment of the position of the jaws using Linear and Angular Measurements Proffit and White have proposed using a perpendicular from the nasion with the TH in assessing the maxillary and mandibular anteroposterior relationship with linear measurements. • 3 suggested linear measurement from points A,B,and pogonion (Pg) to nasion perpendicular to TH relate the position of the maxilla, mandible ,and chin respectively • A- point should be 1 mm in front of the Na – perpendicular, whereas B- point and Pg should be 3mm and 1mm behind the line respectively • Due to the importance of accurate assessment of the anteroposterior position of both the maxilla and the mandible relative to each other and the cranial base,angular measurements are also calculated between the – -TH and NaA – 90 degrees +/-3degrees -TH and NaB – 87 degrees -TH and NaP – 89 degrees +/- 3 degrees •
  71. 71. Assessment of the relative anteroposterior position of the maxilla and the mandible – the true horizontal Wits and the ANB angle • If A and B are projected on the TH through perpendicular lines points A and B are defined,respectively • The AB distance is defined as the true horizontal Wits versus the original Wits on the occlusal plane The TH Wits provides a better and more clear relationship of the anteroposterior position of the jaws relative to each other than does the original Wits ,which can sometimes be affected by the inclination of the occlusal plane or by the inclination of the Frankfort horizontal The Wits appraisal does not necessarily focus attention on changes actually occuring in the sagittal relation between the maxilla and the mandible Rather,because of changes in the angulation of the occlusal plane,the true sagittal changes are likely to be disguised A correlation between angle ANB and Wits would not be expected because they each involve an exclusive point or plane , which is not necessarily biologically related.the mean +/- SD for this measurement is 4 +/-2 mm In addition to the TH Wits linear measurement, an angular measurement ,the ANB angle , is also used to assess the anteroposterior position of the jaws • • • • • The mean+/- SD is 3 degrees +/- 2 degrees
  72. 72. Anteroposterior assessment of the chin – the chin length and the BNP angle •A line parallel to the TH is drawn tangent to the mandible at Menton.projections of the B point and Pg define the chin length(BP) •The mean +/- SD for this measurement is 2 +/- 2mm •An angular measurement , the BNP angle , assesses the prominence of the chin relative to the body of the mandible •The mean +/-SD for the BNP angle is -2 degrees +/- 2 degrees
  73. 73. Vertical skeletal assessment  The following 10 cephalometric measurements may aid the clinician in appreciating a patient’s facial vertical growth: Width of the symphysis parallel to the True Horizontal from Pogonion (P TH) • • •  The greater this measurement is ,the more of forward rotation is to be expected A narrow symphysis corresponds to a backward growth rotation The mean +/- SD is 16.5mm +/- 3mm Angle of the symphysis ( BP – MeTH ) • • • • This is defined by the line connecting B-point and Pogonion (P) as it crosses a line parallel to the true horizontal (TH) at Menton (Me) The mean +/- SD is 75 degrees +/- 5 degrees If the symphysis is inclined backwards , that is , if the angle of the symphysis is acute , this is an indication of forward rotational pattern If it is inclined forward (angle is obtuse),there will be backward rotation
  74. 74.  Mandibular plane angle (GoMe–TH) One of the most widely used cephalometric measurements , this angle may sometimes mask the true growth tendencies of the mandible due to extensive remodelling changes occuring at the angle of the mandible and the symphysis • High values indicate a backward growth rotator,and low ones indicate a horizontal growth pattern • The mean +/- SD is 27 degrees +/-5 degrees.the angle will decrease approximately 2 degrees +/- 2 degrees from childhood to adulthood. Sum of posterior angles • The mean value of the sum of the cranial flexure angle SNa – SAr (saddle angle),Articular angl (SAr – ArGo) and gonial angle (ArGo-GoMe) is 396 degrees +/- 4 degrees • High values indicate a vertical growth pattern (clockwise,opening or backward rotation),whereas low ones show a horizontal growth pattern (counter clockwise,closing or forward growth rotation) • The mean +/-SD of the individual angles is: SNa – SAr – 123 +/-5 degrees SAr - ArGo – 143 degrees +/- 6 degrees ArGo – GoMe – 130 degrees +/- 7 degrees Gonial angle (ArGoMe) • Described by Bjork and Jarabak and Fizell , with a mean of 130 degrees +/-7 degrees , an increased gonial angle indicates a backward growth rotator, and a decreased one indicates a forward growth rotator •  
  75. 75. • Gonial angle ratio • • • • Posterior cranial base to Ramus height ratio (SAr :ArGo) • • • • A line from Gonion to Nasion divides the gonial angle into upper (ArGoNa) and lower (NaGoMe). If the ratio of the upper to the lower angle is more than 75% (high upper angle ) – indicates increased horizontal growth rotation The opposite – high lower angle indicates a vertical growth pattern The length of the posterior cranial base needs to be measured and compared to the mean for the individual sex and the age group Providing that the length of Ar is within normal limits , a ratio value of more than 75 % would indicate a short ramus height,thus contributing to a clockwise rotation skeletal pattern A short posterior cranial base is also indicative of a backward growth rotator Posterior / Anterior face height ratio ( SGo : NaMe ) • Values higher than 65% - forward growth pattern , ratio of less than 65% - backward growth rotator
  77. 77. Eight methods of analysing a cephalogram to establish the A-P skeletal discrepancy – BJO 1981 vol 8 • • • • • • • • Downs analysis Steiner analysis Eastman analysis Bjork analysis Ricketts analysis Tweed analysis Wits analysis Wylie analysis
  78. 78. Eight methods of analysing a cephalogram to establish A-P skeletal discrepancy The 8 analyses use between them three occlusal planes 1.A line joining the midpoint of the overlap of the mesio-buccal cusps of the upper and lower first molars with the point bisecting the overbite of the incisors.this is used by Downs and Steiner 2.The functional occlusal plane - A line joining the midpoint of the overlap of the mesio-buccal cusps of the first molars and the buccal cusp of the pre molars or deciduous molars 3. A line joining the mid section of the molar cusps with the tip of the upper incisor, used by Bjork Three mandibular planes are used 1.The tangent to the lower most border of the mandible, used by Tweed and Ricketts 2.The line joining the Gonion and Menton used by Downs and Eastman analysis 3.The line joining the Gonion and Gnathion,used by Steiner
  79. 79. A new approach of assessing Sagittal discrepancies : The beta angle • • • • A new angle – beta angle – developed as a diagnostic aid to evaluate sagittal jaw relationship 3 skeletal landmarks – point A , point B , and apparent axis of the condyle 3 lines – line connecting centre of condyle C with B line connecting A and B points line from point A perpendicular to the CB line Beta angle – angle between the last perpendicular to the C-B line
  80. 80. Beta angle between 27degrees-35 degrees - class I skeletal pattern less than 27 degrees – class II greater than 34 degrees – class III • Beta angle enriches the current cephalometric tools available to the clinician and enables better diagnosis and treatment planning for the patients •
  81. 81. Summary : -salient points of cephalometric analysis for the use of functional appliance therapy • Allows anomalies to be located and differentiations made between skeletal and dentoalveolar malocclusions • Helps determine primary and secondary dysplastic structures and possible autonomous compensatory responses before treatment begins • Allows the determination of whether the jaw bases are anteriorly or posteriorly positioned , short or long • In the vertical plane the possible rotations of the maxillary and mandibular bases can be observed and the growth pattern delineated • Assessment of the influences of neuromuscular dysfunction on the dentition – vital for diagnosis and treatment planning with functional appliance
  82. 82. References : • • • • • • • • Petrovic – Dentofacial orthopedics with functional appliance Graber and Neumann – Removable orthodontic appliances Rakosi and Jonas – Orthodontic diagnosis Alexander Jacobson – Radiographic cephalometry Thomas Rakosi – Cephalometric Radiography Chong Yol Baik – AJO July 2004 Moira Brown – BJO Vol 8 , 1981 D.Millett and J.F.Gravely – BJO 1991
  83. 83. THANK YOU Leader in continuing dental education