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Class III Malocclusion - Dr. Nabil Al-Zubair

  1. 1. CLASS III MALOCCLUSION
  2. 2. Class III malocclusion A malocclusion that is: Very easy to identify but is often Difficult to treat
  3. 3.  This condition represents a pre-normalcy where the mandible is in a mesial relation to the upper arch  According to Angle Class III molar relationship refers to a condition where the mesio-buccal cusp of the upper first mol or occludes between the mandibular first and second molars.  Although this definition represents a typical Class III relationship, the lower molar can be in a mesial relationship to a varying degree.
  4. 4. ETIOLOGY True Class III malocclusion exhibits (Underlying skeletal imbalance) usually inherited have a very strong GENETIC basis. Habitual forward positioning of the mandible (Psudo Class III) Occlusal prematurities Enlarged adenoids
  5. 5. Causes of an reversed overjet cause Aetiology Skeletal pattern (Class III) - Long mandible - Forward placement of glenoid fossa positioning the mandible more anteriorly - Short and/or retrognathic maxilla - Short anterior cranial base Anterior mandibular displacement on closure - Premature contact Retained primary upper incisors These may deflect the eruption path of their successors palatally into crossbite Restrained of maxillary growth - Found in repaired cleft lip & palate & attributed to the effect of postsurgical scar tissue
  6. 6. cause Aetiology Skeletal pattern (Class III) - Long mandible - Forward placement of glenoid fossa positioning the mandible more anteriorly - Short and/or retrognathic maxilla - Short anterior cranial base Causes of an reversed overjet
  7. 7. cause Aetiology Anterior mandibular displacement on closure - Premature contact Causes of an reversed overjet
  8. 8. Retained primary upper incisors These may deflect the eruption path of their successors palatally into crossbite
  9. 9. Causes of an reversed overjet cause Aetiology Skeletal pattern (Class III) - Long mandible - Forward placement of glenoid fossa positioning the mandible more anteriorly - Short and/or retrognathic maxilla - Short anterior cranial base Anterior mandibular displacement on closure - Premature contact Retained primary upper incisors These may deflect the eruption path of their successors palatally into crossbite Restrained of maxillary growth - Found in repaired cleft lip & palate & attributed to the effect of postsurgical scar tissue
  10. 10. 1. Growth modification 2. Orthodontic correction 3. Surgery Treatment modalities
  11. 11. Growth modification Class III malocclusion should be recognized and treated early due to the following reasons:
  12. 12. The reasons for early treatment : 1. To correct the anterior displacement of the mandible before the ERUPTION of the CANINES and PREMOLARS so that they can be guided into a Class 1 Relationship
  13. 13. The reasons for early treatment : 2. To provide space for the eruption of the BUCCAL segments as a result of Proclination of the upper incisor
  14. 14. The reasons for early treatment : 3. to provide a normal environment for the growth of the maxilla by Elimination the Anterior Crossbite
  15. 15. The reasons for early treatment : To this should be added 4. Psychological benefits resulting from improved dental and facial appearance.
  16. 16. Interception during growth
  17. 17. Orthopedic appliance
  18. 18. What is Orthopedic appliance ?  Orthopedic appliance that allows orthodontists to control growth of facial structures  Various designs  Used with growing patients
  19. 19. Class II Correction Class III Correction (excess growth of maxilla/ (deficient growth of deficient growth of mandible) maxilla/excess growth – Cervical Headgear of maxilla) – High Pull Headgear – Reverse Pull Headgear – Chin Cup – Combination
  20. 20. Interception during growth The following are some of the growth modulation procedures that can be carried out: a. Frankel III, a mayofunctional c. Chin cup with high pull headgear is used to intercept Class III appliance can be used during malocclusion due to mandibular growth to intercept Class III due prognathism. to maxillary skeletal retrusion. d. Severe Class III malocclusions that b. Reverse activator. are a result of maxillary retrusion can be treated by reverse headgear or face mask to protract the maxilla
  21. 21. Orthopaedic change in class 3 malocclusions  The possible effects of orthopaedic treatment in class 3 malocclusions. 1. Stimulation of maxillary growth ( 50% ) as measured by SNA. 2. Inhibition of mandibular projection ( 90% ) as measured by SNB. The annual change expected was calculated as 1.8° in ANB.
  22. 22. Mandibular skeletal appliances (CHINCAPS)  The use of CHINCAPS was a popular treatment modality Based on the belief that The mandible was the major contributor to the class 3 malocclusion.
  23. 23. Mandibular skeletal appliances (CHINCAPS) Chincap therapy was effective in Reducing Before PUBERTY Mandibular Prognathism But this advantage was then lost.
  24. 24. Chin Cup Therapy 1. Mild skeletal problem (PSEUDO CLASS III) 2. Short Vertical Face height because causes longer facial height 3. Requires normally positioned or proclined lower incisors because it will retrocline incisors
  25. 25. Effects of Chin Cup Therapy 1 - Lingual tipping of the mandibular incisors – leading to crowding Change in direction 2 - Change in direction of mandibular growth (Downward and backward)  May lead to skeletal open bites in patients with initially increased lower anterior facial height
  26. 26. Maxillary skeletal appliances ( Reverse Pull Headgear)  (Require a Very Cooperative Patient)  Used to apply an anteriorly directed force, via ELASTICS, on the maxillary teeth and maxilla  This technique useful in Class III associated with a CLP anomaly & hypodontia where forward movement of the buccal segment teeth to close space is desirable.
  27. 27. Reverse Pull Headgear / face mask  Side effects include  downward and backward rotation of the mandible  Lingual tipping of the mandibular incisors
  28. 28. Timing of Any Orthopaedic Treatment  Females – 8.5-10.5 years old  – In general, if menses have occurred, most of the rapid growth has already occurred and headgear will not be very helpful  Males – 9.5-11.5 years old
  29. 29. Treatment planning in class III malocclusions
  30. 30. Treatment planning in class III malocclusions  Many factors should be considered before planning the treatment: 1. The patients opinion regarding their occlusion and facial appearance. 2. The severity of the skeletal pattern. 3. The expected pattern of future growth. 4. Dento-alveolar compensation. 5. The degree of crowding.
  31. 31. Regarding their occlusion & facial appearance 1. PATIENT'S OPINION (needs to be approached with some tact).
  32. 32. 2. Severity of skeletal pattern: both - Anteroposteriorly & - Vertically (The major determinant of  the difficulty &  prognosis of orthodontic treatment).
  33. 33. Envelop of discrepancy Inner envelop : orthodontic treatment Middle envelop : orthodontic treatment + growth modification Outer envelop : orthognathic surgery
  34. 34. 3. Expected pattern of further growth: both anteroposteriorly & vertically Children with increased vertical proportions The average growth tend to often continue to exhibit Worsening a vertical pattern of the relation between growth the arches. which reduce the overbite.
  35. 35. Treatment planning in Class III malocclusions: In Class III malocclusions Normal or increased overbite is an advantage  as a vertical overlap of the upper incisors with the lower incisors post-treatment is vital for stability.
  36. 36. 4. If the patient can achieve an edge-to-edge incisor position : Increase the prognosis of correction the incisor relationship.
  37. 37. 5. Dento-alveolar compensation:  orthodontic treatment aimed to increase it,  if it already present, trying to increase it further may not be an aesthetic or stable treatment option.
  38. 38. 6. Degree of crowding:  crowding occurs more frequently, and to a greater degree, in the upper arch.  Extractions should be resisted as it worsening the incisor relationship.  Where upper extractions are necessary, it is advisable to extract at least as forwards in the lower arch.
  39. 39. 1. Expansion the arch Anteriorlly to correct anterior X-bite. 2. Expansion the arch Buccoligually to correct buccal segment X-bite. 3. Distal movement of the upper buccal segment with Headgear To relief upper arch crowding
  40. 40. To relief upper arch crowding  Additional space can be gained by  Expansion the arch Anteriorly to correct the incisor relationship and/or
  41. 41. To relief upper arch crowding  Additional space can be gained by 1. Expansion the arch Buccoligually to correct buccal segment X-bite.
  42. 42. Expansion of the upper arch to correct a X-bite  will have the effect of reducing overbite, which is a disadvantage in Class III  (overbite reduction occurs because expansion of the upper arch is achieved primarily by tilting the upper premolars & molars buccaly) palatal cusps swinging and ‘propping open’ the occlusion.
  43. 43. Expansion of the upper arch  If upper arch expansion is indicated & the overbite is reduced Fixed Appliances should be used to limit tilting of upper molars buccally during expansion.
  44. 44. Expansion of the upper arch to correct a X-bite
  45. 45. To relief upper arch crowding  Distal movement of the upper buccal segment with Headgear to gain space for alignment is inadvisable (restraining growth of maxilla).
  46. 46. To relief upper arch crowding  Mild to Moderate Crowding space can be made by a Combination of 1. forward movement of the incisors & 2. distal movement of the remaining buccal segment teeth.
  47. 47.  Functional appliances  can be useful in mixed dentition where a combination of  Proclination of the upper incisors together with  Retroclination of the lower incisors is required.
  48. 48. Orthodontic correction
  49. 49. Orthodontic correction  Can be achieved by either (i)- Proclination of the upper incisors alone or (ii)- Retroclination of the lower incisors with or without proclination of the upper incisors.
  50. 50. Orthodontic correction  This determined by: – Skeletal pattern & – Amount of overbite present before treatment
  51. 51. Orthodontic correction – Amount of overbite present before treatment Proclination of the Overbite upper incisors Retroclination of the Overbite lower incisors
  52. 52. Treatment options:
  53. 53. Treatment options: 1. Accepting the incisor relationship: (a) - in mild cases where the overbite is minimal; (b) - if the remainder of the family have a similar facial appearance.
  54. 54. 2. Proclination of the upper labial segment: Best carried out in the mixed dentition when the canines are Unerupted and High Above the roots of the upper lateral incisors.
  55. 55. Proclination of the upper labial segment: Correction of the incisors relationship by proclination of the upper incisors only can be considered in cases with the following features: a) A Class I or mild Class III skeletal pattern. b) The upper incisors are not already proclined. c) An adequate overbite will be present at the end of treatment to retain the corrected position of the upper incisors.
  56. 56. 3. Retroclination of the lower labial segment with or without proclination of the upper labial segment:  In those cases with  a mild to moderate Class III skeletal pattern, or  where there us reduce overbite,  A combination of retroclination of the lower incisors and proclination of the upper incisors will achieve correction of incisors relationship.
  57. 57. To advance the upper incisors & retrocline the lower incisors Removable appliances Functional appliances Fixed appliances: tooth movements are accomplished more efficiently
  58. 58. To advance the upper incisors & retrocline the lower incisors Removable appliances Early mixed dentition. Functional appliances Permanent dentition. Fixed appliances: tooth movements are accomplished more efficiently
  59. 59. For retroclination the lower labial segment  Space is required in the lower arch & Extractions are required unless the arch is spaced naturally.
  60. 60. Role of extractions Extraction of the lower deciduous canines may  Allow the lower incisors to drop lingually and  Assist in the correction of the reverse overjet.
  61. 61. Role of extractions  Class III malocclusion characterized by upper arch length deficiency and anterior cross bite can be treated by extracting the lower first premolars followed by fixed mechanotherapy.  In case of arch length deficiency involving both the arches, the first premolars should be extracted in both the upper and lower arches.
  62. 62. 3. Retroclination of the lower labial segment with or without proclination of the upper labial segment:  Use of a ROUND archwire in the lower arch & a RECTANGULAR arch in the upper arch help to correct the incisors relationship.  Intermaxillary Class III elastic traction from the lower labial segment to the upper molars can also be used to help move the upper arch forwards & the lower arch backwards (care required to avoid extrusion of the molars which will reduce overbite.
  63. 63. Surgery:  Sever skeletal pattern and/or  reduced overbite or  an anterior openbite (Precludes ‫ يعوق‬orthodontic alone)
  64. 64. Surgery: ANB Surgery is almost required if the value for ANB ⁰ < – 4° & The inclination of the lower incisors to the mandiblar plane < 83°.
  65. 65. Treatment of severe Class III after growth Class III Maxillary deficiency Maxillary advancement procedures such as Le Fort I osteotomy.
  66. 66. Treatment of severe Class III after growth Class III Mandibular prognathism Mandibular set back procedures Body ostectomy
  67. 67. Surgery Genioplasty reduction
  68. 68. Class III  Dental  Dental with underlying skeletal component  Maxillary deficiency  Mandibular excess  Combination of maxilla and mandible
  69. 69. Frequent Soft Tissue Findings – Frontal View  Narrow alar base  Deficient zygomatic, paranasal, infraorbital areas  Midface deficiency  Thin vermilion border  Decreased maxillary incisor exposure at rest  Reduced upper lip length
  70. 70. Frequent Soft Tissue Findings – Profile View  Mandibular prognathism  Well defined mandibular border  Normal neck-chin angle of 120 degrees  Midface deficiency
  71. 71. Frequent Dental / Intraoral Findings  Mesiocclusion of molars and canines  Crossbite tendency  Buccal crown tipping of maxillary molars
  72. 72. Frequent Dental / Intraoral Findings  Decreased attached gingiva for mandibular anterior dentition  Maxillary retrognathism – Often absent or undersized maxillary lateral incisors – Maxillary dental crowding in canine/premolar area

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