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Etiology of Malocclusion I
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Etiology of Malocclusion I

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Introduction to Orthodontics

Introduction to Orthodontics
Fifth Year

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Etiology of Malocclusion I Etiology of Malocclusion I Presentation Transcript

  • Seventh Lecture Etiology of Malocclusion
  • Angle’s classification Class I malocclusion: Lower dental arch is in normal anteroposterior relation to upper dental arch as evidenced by occlusion of mesiobuccal cusps of upper first permanent molars in buccal groove of the lower first permanent molars. March 5, 2012 Dr. Ahmed Basyouni 2
  • In Angle’s Class I, mesiodistal relationship of first molars are normal, but malocclusion exists into one or more of the following three categories: A. Local abnormalities: 1. Crowding of upper and lower incisors. 2. labial inclination of anterior teeth. 3. Anterior cross bite. 4. Posterior cross bite. 5. Local abnormalities due to premature loss of decid. molars with loss of space in the premolar region. March 5, 2012 Dr. Ahmed Basyouni 3
  • March 5, 2012 Dr. Ahmed Basyouni 4
  • B. Vertical malrelationship: May be either deep or deficient overbite. C. Disproportion in size between basal bone and teeth: Basal bone may be either too large resulting in spacing or too small resulting in crowding of upper and lower teeth & impactions of third molars. March 5, 2012 Dr. Ahmed Basyouni 5
  • Class II malocclusion: Lower dental arch is in distal relation to upper dental arch as evidenced by occlusion of mesiobuccal cusp of the upper first permanent molar in the embrasure between lower first permanent molar and lower second premolar. It is measured in terms of units i.e. width of one premolar is considered one unit (or ½ width of one molar). March 5, 2012 Dr. Ahmed Basyouni 6
  • There are two divisions of Class II. They are affecting bilaterally the dental arch. Division 1: This is usually characterized by: 1. The upper incisors are proclined. 2. Increased overjet. 3. There is often short upper lip with failure in anterior lip seal. 4. V-shaped upper arch i.e. narrow in the canine and premolar region and broadening between the molars. 5. The mandible may be deficient and chin underdeveloped. Class II div.1 March 5, 2012 Dr. Ahmed Basyouni 7
  • Division 2: This is usually characterized by: 1. The upper central incisors show lingual inclination & may be overlapped by the upper lateral incisors. 2. The upper arch is usually broad. 3. Deep incisor overbite, both upper & lower incisors are in apparent supra-occlusion. 4. The upper lip is of normal length and contacts the lower lip with deep mental groove below lower lip. 5. The mandible is frequently of good size. Class II div. 2 March 5, 2012 Dr. Ahmed Basyouni 8
  • Comparison between Class II div. 1 & div. 2 Feature Division 1 1.Upper incisors Proclinated 2. Upper arch 3. Upper lip V-shape Short – failure of lip seal 4. Mandible Deficient chinunderdeveloped 5. Overbite Deep, lower incisors near palatal mucosa 6. Angle’s Class Class II March 5, 2012 Dr. Ahmed Basyouni Division 2 Retroclined central incisors & overlapped with lateral incisors Broad Normal length Good size Deep, upper & Lower incisors in supraocclusion Class II 9
  • Class III malocclusion: Lower dental arch is in mesial relation to upper dental arch as evidenced by occlusion of mesiobuccal cusp of upper first permanent molar in the embrasure between lower first & second permanent molars. March 5, 2012 Dr. Ahmed Basyouni 10
  • General Causes Local Causes March 5, 2012 Dr. Ahmed Basyouni 11
  • A. General Causes 1. Evolution: In the evolutionary scale, there is gradual reduction of jaw sizes, so crowding of teeth and impacted wisdoms become more common. March 5, 2012 Dr. Ahmed Basyouni 12
  • A. General Causes 2. Congenital malformation: Congenital malformation Environmental Hereditary Chromosomal March 5, 2012 Dr. Ahmed Basyouni Genetic 13
  • A. General Causes 2. Congenital malformation: Definition: Defects occur during intrauterine life and detected at birth or during infancy, Congenital malformations may be due to: i. Environmental causes: a. Infective agents e.g. viruses (German measles) b. Exposure to radiation Repaired Cleft March 5, 2012 Dr. Ahmed Basyouni 14
  • A. General Causes 2. Congenital malformation: i. Environmental causes: c. Drugs with teratogenic effects d. Hormones e. Nutritional disorder f. Smoking, alcohols & caffeine g. Maternal defects March 5, 2012 Dr. Ahmed Basyouni 15
  • A. General Causes 2. Congenital malformation: ii. Hereditary causes: – Chromosomal – Genetic March 5, 2012 Dr. Ahmed Basyouni 16
  • ii. Hereditary causes A. General Causes 2. Congenital malformation: a. Chromosomal abnormalities: e.g. Trisomy 21(Down’s Syndrome) or mongolism: Mental retardation, flat nasal bridge, fissured protruding tongue & macroglossia. March 5, 2012 Dr. Ahmed Basyouni 17
  • A. General Causes 2. Congenital malformation: b.Genetic: due to defective genes, there will be: - Achondroplasia - Cleidocranial dysostosis: Retarded eruption of permanent teeth, Short & thin roots of permanent teeth, supernumerary teeth. - Mandibulofacial dysostosis. - Dentinogenesis imperfecta. March 5, 2012 Dr. Ahmed Basyouni Cleidocranial dysostosis Achondroplasia 18
  • A. General Causes 3. Endocrinal disturbances: March 5, 2012 Dr. Ahmed Basyouni 19
  • A. General Causes 3. Endocrinal disturbances: Hypo or hyperpituitarism: would affect growth hormone resulting in Dwarfism, or Gigantism /Acromegally. March 5, 2012 Dr. Ahmed Basyouni 20
  • A. General Causes 3. Endocrinal disturbances Hypothyroidism: -Abnormal resorption pattern -Retained decid. teeth -Delayed eruption of teeth March 5, 2012 Dr. Ahmed Basyouni 21
  • A. General Causes 4. Nutritional deficiency: March 5, 2012 Dr. Ahmed Basyouni 22
  • A. General Causes 4. Nutritional deficiency Vit. D deficiency Ricketts (Hypocalcemia): Hyperexcitability of musc.(medial pterygoid musc.), on soft bone will produce obtuse gonial angle open bite March 5, 2012 Dr. Ahmed Basyouni 23
  • A. General Causes 5. Pathological Conditions: March 5, 2012 Dr. Ahmed Basyouni 24
  • A. General Causes 5. Pathological Conditions: Systemic diseases that upset the developmental time scale (e.g. eruption, resorption) might have permanent effect. (e.g. diabetes) March 5, 2012 Dr. Ahmed Basyouni 25
  • A. General Causes 5. Pathological Conditions: Diseases with muscle malformation such as atrophy, cerebral palsy have characteristic effects on the dental arch. March 5, 2012 Dr. Ahmed Basyouni 26
  • B. Local Causes 1. Congenital missing teeth: Hereditary ectodermal dysplasia associated with partial anodontia (Oligodontia), a dry coarse skin, fine hair, defects of the nails and absence of sweet glands. Ectodermal dysplasia March 5, 2012 Dr. Ahmed Basyouni 27
  • B. Local Causes 1. Congenital missing teeth: The most common missing teeth are: upper & lower third molars, upper lateral incisors, & lower second premolars. In case Of Missing laterals: Maxillary canines may erupt mesially into space of missing laterals Or may give rise to a median diastema March 5, 2012 Dr. Ahmed Basyouni 28
  • Causes of maxillary median diastema: 1. Physiological spacing of permanent central incisors is normal at 7.5 years of age (Ugly Duckling Stage) and tend to close with eruption of lateral incisors and finally canines. 2. Familial pattern. 3. Small teeth in large jaws. 4. Missing lateral incisors. 5. Misplaced lateral incisors. March 5, 2012 Dr. Ahmed Basyouni 29
  • Causes of maxillary median diastema: 6. Peg shaped lateral incisors. 7. Supernumerary tooth or teeth between central incisors e.g. mesiodens. 8. Median cyst. 9. Abnormal labial frenum. 10. Imperfect fusion at midline of premaxilla. March 5, 2012 Dr. Ahmed Basyouni 30
  • B. Local Causes . Congenital missing teeth: In case of Missing lower second premolar: Deciduous second molar is usually retained, & lower first permanent molar will be found slightly distal to its opposing upper first permanent molar, this is due to the larger mesiodistal diameter of second decid. Molar as compared to that of second premolar. March 5, 2012 Dr. Ahmed Basyouni 31
  • Missing upper laterals & lower second premolars: March 5, 2012 Dr. Ahmed Basyouni 32
  •  . Supernumerary B. Local Causes teeth: They are commonly associated with congenital defects as cleft palate. Mesiodens frequently seen near midline palatal to upper incisors. Removal of supernumerary teeth allows normal teeth to erupt or return to their correct positions (self correction) or through appliance therapy. March 5, 2012 Dr. Ahmed Basyouni Mesiodent 33
  • B. Local Causes 2 Supernumerary teeth: There are 4 main types: a. Peg teeth, small conical shaped teeth often appearing in the midline of upp. Centrals. b. Multicusped teeth with deep occlusal pits ( tuberculated like premolars). c. Supplemental teeth of normal size and appearance. d. Teeth of normal shape but of larger or smaller size. March 5, 2012 Dr. Ahmed Basyouni 34
  • B. Local Causes 2 Supernumerary teeth: Localization of supernumerary teeth assessed as follows: 1. Inspection & palpation. 2. Radiographs: a. Occlusal, & periapical films b. Method of Parallex: Two radiographs are taken with film placed in same position each time, but tube is moved about 4 inches, if the shadow of the unerupted tooth moves same direction as the tube, then it is lying palatally. March 5, 2012 Dr. Ahmed Basyouni 35
  • Summary General Causes Local Causes 1.Evolution: 2. Congenital malformation: 3. Endocrinal disturbances: 4. Nutritional deficiency 5. Pathological Conditions: March 5, 2012 1. Congenital missing teeth: 2 Supernumerary teeth: & continue on next Lecture . Dr. Ahmed Basyouni 36
  • March 5, 2012 Dr. Ahmed Basyouni 37