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Class iii malocclusion

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treatment planning of class III malocclusion

Published in: Health & Medicine

Class iii malocclusion

  1. 1. Presented by: Tooba Gul
  2. 2.  According to British standards Incisor classification, in class III malocclusion the lower incisor edges lie anterior to the cingulum plateau of the upper incisors. The overjet is reduced or reversed.  According to Angle’s classification, in class III the mesiobuccal cusp of the lower first molar occludes mesial to the class I position.
  3. 3. Aetiology  Skeletal pattern  Dental factors  Soft tissues  Specific conditions  Familial tendency
  4. 4. Skeletal Pattern  Most important aetiological factor  Skeletal pattern can be any of the following: 1. Mandibular prognathism 2. Maxillary retrognathism 3. Combination of both
  5. 5. Features of class III malocclusion  A concave facial profile  A retrusive nasomaxillary area  Prominent lower third of the face  Narrow upper arch  Reduced or reversed overjet
  6. 6. Concave facial profile Reversed overjet
  7. 7. Diagnosis  A successful treatment plan depends on an accurate diagnosis  For treating class III malocclusion a direct cause must be identified, that is, true class III should be differentiated from pseudo class III malocclusion.
  8. 8. Pseudo Class III Malocclusion  Pseudo class III malocclusion is a habitual established cross bite of all anterior teeth, without any skeletal discrepancy, resulting from functional forward positioning/shift of the mandible on closure.  Causes include:  occlusal prematurity  Enlarged adenoids
  9. 9. How to differentiate between a true class III and pseudo class III malocclusion?  Mandible should be guided in a centric relationship, this will reveal a normal overjet or edge to edge incisor relation in pseudo class III  On cephalometric analysis, pseudo class III malocclusion shows a normal SNA if diagnosed early, whereas SNB could be slightly increased because of forward positioning of the mandible.  In contrast, in true class III cases, a large SNB angle or a small SNA angle may be found, depending on whether the result is due to an underdeveloped maxilla or a long mandibular base, or both.  Most true class III cases have a strong hereditary component
  10. 10.  The final diagnosis of the type of class III malocclusion relies heavily on: (i) clinically establishing the dual closure pattern by asking and guiding the patient to bite in normal centric and habitual positions, (ii) observing any familial tendency, (iii) cephalometric parameters (iv) incisor relationships.
  11. 11. Treatment objectives  To achieve growth modulation in skeletal case  To relieve crowding and produce alignment of teeth  To correct incisor relationship to obtain normal overjet and overbite  To achieve stable molar relationship
  12. 12. Factors considered while treatment planning  Patient’s opinion  Severity of skeletal pattern  Amount and expected pattern of future growth  Degree of crowding  If an edge to edge incisor contact can be achieved or not  Amount of dento-alveolar compensation present
  13. 13. Treatment modalities  Growth modification  Orthodontic camouflage  Orthognathic surgery
  14. 14. Growth Modification  In young patients who are still in their growing phase orthopedic and myo- functional appliances can be used in cases of skeletal class III malocclusion.  Either there is deficient growth of maxilla or excess growth of mandible.
  15. 15. FRANKEL III FUNCTIONAL APPLIANCE  Used in mild skeletal problems  Causes downward and backward rotation of the mandible  Has little or no effect on maxilla
  16. 16. Reverse pull headgear (facemask)  Indicated in patients with retrusive maxilla  Obtains anchorage from forehead and chin  Exerts force on maxilla via elastics that attach to maxillary splints  Effects include: 1. Forward and downward movement of maxilla 2. Downward and backward rotation of mandible 3. Lingual tipping of lower incisors
  17. 17.  Treatment given at the mixed dentition is advocated by most researchers.  Requires great patient cooperation.
  18. 18. Chin Cup Therapy  An effort to restrain mandibular growth  Redirects mandibular growth in a more vertical direction  Ideal in patients with  mild skeletal problem  reduced lower anterior facial height  normal or proclined lower incisors  Most of the reported studies recommended an orthopedic force of 300 to 500 g per side  Patients are instructed to wear the appliance 14 hours per day.
  19. 19. Vertical pull chin cup Occipital pull chin cup
  20. 20. Orthodontic Camouflage  Proclination of the upper labial segment  Retroclination of the lower labial segment  Combination of both  Extraction pattern may vary from extraction of lower first bicuspids only to extraction of upper second premolar and lower first premolar and sometimes even lower incisor
  21. 21. Proclination of upper labial segment  Correction of incisor relationship by proclination of the upper incisors can only be considered with the following features:  a class I or mild class III skeletal pattern  The upper incisors are not already significantly proclined  Adequate overbite will be present at the end of treatment to retain the corrected position of the upper incisors
  22. 22. Retroclination of lower labial segment  In cases with mild to moderate class III skeletal pattern or in case of reduced over bite  Space is required in the lower arch for retroclination of lower labial segment and extractions are required
  23. 23. Orthognathic Surgery  In some cases the severity of skeletal pattern and/or the presence of a reduced overbite or an anterior open bite precludes orthodontics alone.  Orthognathic surgery is almost always indicated if: Value of ANB is -4 Inclination of lower incisors to mandibular plane is 83
  24. 24. Common Surgical Procedures  Lefort I maxillary advancement For retrognathic maxilla  bilateral saggital split (BSSO) mandibular setback For prognathic mandible  Surgically assisted RPE
  25. 25. Maxillary Advancement
  26. 26. Mandibular setback
  27. 27. SUMMARY: Treatment of Class III Malocclusion  Non-growing patients 1. Acceptance 2. Orthodontic Camouflage 3. Orthognathic Surgery  Growing patients 1. Acceptance 2. Functional orthopedic appliances 3. Orthodontic Camouflage

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