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AETIOLOGY AND CLASSIFICATION OF MALOCCLUSION Rav Govender BChD; MFDS RCS Edin.; MSc. Lond.; MORTH RCS Eng. Learning objectives • CLASSIFICATION • AETIOLOGY Skeletal Factors Soft Tissue Factors, often not recognised Dental factors Habits Iatrogenic Factors / local Case Discussions AETIOLOGY Complex multifactorial Genetically determined, both local and skeletal factors eg. class III, a skeletal factor and hypodontia a local factor are both genetically determined. Specific genetic syndromes, Pierre Robin or acromegaly Environmental factors / Trauma, Local Complex interactions among multiple factors that influence growth and development. CLASSIFICATION • Dental • Skeletal Dental • British standards institute OR BSI • Angle’s classification • Andrews classification The British standards institute is based on the incisor relationship. Angle’s and Andrews classification is based on the molars relationship. BSI The overjet should be 2-4mm with a vertical overlap of one third of the crown of the lower incisors. Classification by molar relationship Andrew Angle A. The distal surface of the upper first molar occludes with the mesiobuccal cusp of the lower second permanent molar ANDREW B. The mesiobuccal cusp of the upper first permanent molar occludes with t he buccal groove of the lower first permanent molar. ANGLE C. Half class II D. Full unit class II Canine classification CLASS I Class II CLASSIFICATION SKELETAL: Antero-posterior vertical Transverse Mild moderate and severe In 3 planes SKELETAL I PATTERN ORTHOGNATHIC/ STRAIGHT PROFILE Angle ANB 2° - 4° SKELETAL II PATTERN CONCAVE PROFILE ANB EXCEEDS 4° SKELETAL II Usually due to mandibular retrognathia. Ceph. Study By Mc Namara et. al. Class II is not a single entity, But mandibular skeletal retrusion most common. Small % is maxillary protrusion Almost half the sample had excessive vertical dimension. CLASS II INCISOR RELATIONSHIP These diagrams show how partial reduction of the overjet does not allow the lip to cover the upper incisors. The upper incisors will return to their pre-treatment position. SKELETAL III PATTERN CONVEX PROFILE ANB LESS THAN 2° SKELETAL III Caused by maxillary deficiency and /or mandibular prognathism. Definitive familial and racial tendency for mandibular prognathism. Maxillary deficiency not clear, but environmental factors unlikely. Hapsburg jaws. Royal Family in Spain that ruled around 1660 Hapsburg Jaws • Class I the mandible is 2 -3 mm posterior to the maxilla • Class II the mandible is retrusive relative to the maxilla • Class III the mandible is protrusive relative to the maxilla CLASSIFICATION Vertical assessment, Inherited Assessment of lower facial height. The distance x from a point between the eyebrows to the base of the nose is equivalent to the distance y from the base of the nose to the chin. CLASSIFICATION Vertical assessment CLASSIFICATION Vertical skeletal assessment Frontal view, assess the vertical and transverse discrepancy. Vertical assessment Factors that influence and increase the vertical dimension. Increased vertical dimension: AOB Thumb sucking habit Partial nasal obstruction. Harvold study, Lopatiene et.al Lithuanian study. ( 7- 15 Yr s). The main characteristics of the respiratory obstruction syndrome hypertrophied tonsils or adenoids, mouth breathing, open-bite, cross-bite, excessive anterior face height, incompetent lip posture, increased upper incisor show narrow external nares, "V" shaped maxillary arch Vertical assessment Long face syndrome Vertical growth pattern Increased LAFH Downward rotation of the mandible (clockwise rotation) Excessive eruption of molars leading to AOB CLASSIFICATION Vertical assessment Anterior open bites are often associated with an increase in lower anterior face height CLASSIFICATION Vertical assessment Profile of a patient with a much reduced lower anterior facial height. Compare with long face syndrome Low angle patient /short face syndrome Horizontal growth pattern Increased overbite Decreased LAFH Upward and forward rotation of the mandible, i.e. anticlockwise rotation of the mandible. Increased eruption of the mandibular teeth, i.e. incisors Both forward and backward growth rotations results in LLS crowding, right until the late thirties. (Bolton Brush Study by Holly Broadbent, 1966) CLASSIFICATION Vertical Assessment The reduced lower anterior face height is often associated with a deep bite as shown TRANSVERSE ASSESSMENT The face is divided into fifths. Middle fifth Medial two fifths Outer two fifths Assess from above and behind the patient. (assess facial centre, i.e. mid eye-brow, tip of nose, philtrum of upper lip and chin point should line up Transverse discrepancy True facial asymmetry Apparent facial asymmetry, associated with crossbite and mandibular displacement. Intra-orally check for -crossbite and mandibular deviation -scissor bite and “ “ Compare mand-maxillary arches for shape and size. Clinically Dental centre-lines Check for a cant in the maxillary occlusal plane. ( the patient bites on a tongue spatula and relate to inter-pupillary line). Transverse discrepancy Asymmetric condylar growth. Deviation of the lower dental midline to the left. Asymmetries are more common in class II and class III malocclusions. Intra orally THE ROLE OF THE SOFT TISSUES, IN THE AETIOLGY OF MALOCCLUSION Lips Tongue Fraenum Labio-mental fold Nasiolabial angle LIPS Lip competency Lip length Lip tonicity (muscular, or flaccid and everted) Degree of protrusion or retrusion, All these factors are related. THE ROLE OF THE SOFT TISSUES, IN THE AETIOLGY OF MALOCCLUSION LIPS Lip competency, Competent lips can be considered normal and desirable, because • Aesthetics: incompetent lips in conjunction with a short upper lip can lead to the appearance of the patient showing too much upper incisor tooth and gingival tissue on smiling. (Gummy smile) • Function: It provides the patient wit lip-to-lip anterior oral seal during swallowing. • Health: helps prevent gingival drying which can be associated with gingival hyperplasia and gingivitis. THE ROLE OF THE SOFT TISSUES, IN THE AETIOLGY OF MALOCCLUSION LIPS Class II Division I Proclined upper incisors Lip trap STABILITY the upper incisors should be under the control of the lower lip. THE ROLE OF THE SOFT TISSUES, IN THE AETIOLGY OF MALOCCLUSION LIPS Lip incompetence, lips separated at rest by more than 3 – 4 mm. Increased incisal show at rest Protrusion of the upper incisors Lip trap, the lower lip rests behind the upper incisors. THE ROLE OF THE SOFT TISSUES, IN THE AETIOLGY OF MALOCCLUSION Lips Incompetent Flaccid and everted Stability THE ROLE OF THE SOFT TISSUES, IN THE AETIOLGY OF MALOCCLUSION Incompetent Lip length Flaccid and everted, Gingival show Bimaxillary protrusion Stability THE ROLE OF THE SOFT TISSUES, IN THE AETIOLGY OF MALOCCLUSION LIPS Thin Strappy lips Class II Division II THE ROLE OF THE SOFT TISSUES, IN THE AETIOLOGY OF MALOCCLUSION Tongue thrust: usually adaptive. The tongue is placed between the teeth to achieve an anterior oral seal. Endogenous tongue thrust: Rare, On swallowing the tongue is pushed between the upper and lower incisors. Associated with sigmatism (lisping). May also be associated with bimaxillary proclination. An adaptive tongue thrust will cease when a lip to lip contact can be achieved after treatment. Tongue Size: Macroglossia Large Tongue Tongue interposed between the upper and lower incisors. AOB OF 7MM Large tongue LABIOMENTAL FOLD Indicative of Deep bite Reduced lower face height Low mandibular angle THE INFLUENCE OF THE NASIO-LABIAL FOLD Retraction of the upper lip is contra-indicated In adults consider orthognathic inetervention. LOCAL FACTORS IN MALOCCLUSION DEFN: local factors affect one or more adjacent /opposing teeth to produce local disturbances in in dental development. The longer they act more severe the disturbance. • • • • • • Variations in tooth number Abnormalities in tooth position Labial fraenum Trauma Crossbites Dento-alveolar disproportion. Variation in tooth Number Hypodontia, most common upper lateral incisors, lower incisors and lower second premolars. Supernumery teeth Supplemental , dichotomy of tooth germ. Incisor, premolar (extract the most displaced tooth) Early conical forming: offshoot of the dental lamina. Develop between upper centrals. Single but more common multiple. Erupts unless inverted. Causes median diastema. Remove if orthodontics is planned. Late tuberculate forming: thought to represent a third dentition. Develops palatal to 1 / 1, single or multiple Prevents eruption of the incisors Midline Supernumary Odontome Complex: Mix of enamel dentine and cementum Maxillary incisor region Prevents eruption of the incisors Surgical removal and bond an eruption appliance to align the unerupted incisors. Compound odontome: Radiopaque mass of tissue, occurs in the mandible or posterior maxilla. The role of premature loss of primary teeth The factors that determine the outcome: The tooth lost Age of patient Dentoalveolar disproportion, crowding vs spacing. Degree of intercuspation High angle v low angle Management of early loss •Compensatory extractions- to maintain interarch relations. •Balancing extractions- to maintain centreline. •Space maintainers, Advantages and disadvantages. Prolonged retention of primary teeth /ankylosis •Tooth fails to maintain its position in the developing occlusion. More common in the mandible > Ds and Es. Due to, Absence of a successor Genetic, Trauma Pathogenesis: Ankylosis occurs during the reparative phase of tooth resorption, the tooth fails to erupt and the alveolus continues to grow in some cases enveloping the tooth. Effects of prolonged retention primary teeth / ankylosis •Progressive infraocclusion of the primary molar, difficult extraction and lack of alveolar height development. •The permanent successor if present results in delayed eruption, impaction disturbed root formation/ cystic change •Tipping and over-eruption of adjacent and opposing teeth and crowding. Management of infraocclusion Factors to consider before treatment, •Presence or absence of permanent successor •Degree of infraocclusion •Is there a co-existing malocclusion •Long term prognosis of the primary molar Treatment options •Decision based on the above factors Interceptive extraction (absent 5) – spontaneous space closure If there is a malocclusion then orthodontic space closure. Surgical subluxation, break the ankylosis Restorative approach re-establish occlusion 18 15 14 24 25 28 48 45 35 38 Infra-occluding Es are difficult to extract , with minimal damage to alveolus. Abnormalities in tooth form •Fusion, the tooth retains separate pulp chambers. •Gemination, common pulp chamber, •Dilaceration, angulation between the crown and root. Requires a joint orthodontic restorative and surgical approach. Dilaceration Dilaceration Abnormalities in tooth position Most common Maxillary cuspid Genetic Local and environmental factors Important clinical signs, POSITION AND FORM OF 2 / 2 Guidance theory, (peck and peck) Transposition Interchange in position of two permanent teeth, one of which is almost always a canine. Mx: canine and premolar Md: canine and lateral incisor Incomplete, crown overlap only Complete, both crown and apex overley Genetic and environmental Migration during normal eruption Local pathology. Treatment options: Orthodontic alignment of incomplete transposition. Orthodontic alignment in the transposed position Transposition Labial fraenum and the midline diastema 70% cases with a midline diastema associated with a large fleshy fraenum attached to the incisive papilla. Diagnosis: blanching of the incisive papilla on gentle lip retraction. Orthodontic space closure in the absence of fraenectomy has a 84% relapse. Collagenous fibres of a large fraenum disrupt the normal transeptal fibre system between the 1 /1 Radiographically a V shaped crestal notch between the 1 / 1 is seen. Treatment Aim of fraenectomy is to promote the transeptal fibres across the defect. Timing: Must be after the eruption of the 3 / 3. Done just prior to orthodontic space closure. The post op. scar contraction across the defect aides stability. If done after orthodontic space closure, access is limited, and risk of root damage. Crossbites Discrepancy in arch relation, lateral or sagittal mandibular movement as a result of cuspal interference from CR to CO. Aetiology: Skeletal V dental Soft tissue Dentoalveolar Habits, digit sucking Why treat Aesthetics Dental, pain and wear Periodontal loss of attachment TMJ risk Risk of developing of a true asymmetry if left untreated during the developmental stage. Treatment options Address the problem in the primary dentition Removable and fixed appliances Slow expansion v rapid expansion. (RME v quad). Cross arch elastics. Selective grinding of Cs Role of dental trauma in malocclusion Damage to permanent tooth germ from an injury to primary tooth. Type of injury , intrusive v avulsion determines the damage to the successor. Prior to crown formation < 4yrs disturbance in enamel formation resulting in coronal defect. Later injuries will displace the crown relative to the root resulting in dilaceration and impaction of the permanent successor. Treatment will require SE and bonding an eruption appliance. Drift of permanent teeth ffg. early loss of primary teeth. Direct injury of permanent incisor = Avulsion Intrusive injury = Ankylosis Discussion Problems, Mobile 41, Gingival recession of 41 Deep bite If not corrected 41 will have a poor long term prognosis. Appliance design To correct anterior crossbite Problems: severe skeletal III Maxillary hypoplasia peri-nasal flattening thin soft tissues does not camourflage the underlying skeletal III discrepancy. Problems: increased vertical dimension 7mm AOB cuspid to cuspid ms crowded arches bimaxillary proclination 24 crossbite poor rct on 46, guarded prognosis Steep mandibular plane angle Proclination Lip incompetence Increased vertical proportions AOB. Adverse swallowing pattern 46 rct Aims of treatment Address the crowding Correct the crossbite Establish an overbite Level and align the arches. Extraction: 4 4 6 5 Palatal tads to intrude upper buccal segments. Near end treatment Thank you [email protected] WWW.ORTHODONTICSCENTRE.CO.ZA Questions 1. Ankylosis of a primary tooth can result in (a) in its infra-occlusion. T / F (b) delayed root formation in the permanent successor. T/F (c) cystic change in the permanent successor. (d) None of the above. T /F 2. A dilacerated tooth, (a) has genetic aetiology, (b) environmental aetiology (C) None of the above (b) both of the above T/F T /F T/F T/F 3. A large tongue interposed between the upper and lower incisors. (a) causes an anterior openbite. T / F (b) associated with short face syndrome. T / F (c ) proclination of the incisors. T / F (d) none of the above. T/F Questions Deep overbite can be associated with, (a) reduced lower anterior face height. T / F (b) palatal trauma. T / F (c) Stripping of the lower labial gingivae. T / F (d) All of the above. T /F A severe skeletal III discrepancy, (a) has reverse overjet. T / F (b) Dental compensation for the underlying skeletal III base. T/F (c) Best addressed with joint orthodontic / orthognathic intervention. T / F (d) All of the above. T / F