First bds lecture development of occlusion 2


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Development of Occlusion-Orthodontic Lecture note

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First bds lecture development of occlusion 2

  1. 1. Deciduous dentition
  2. 2. Prerequisite knowledge <ul><li>Growth & development of face and jaws both prenatal and postnatal </li></ul><ul><li>Eruption of teeth timing and sequence </li></ul><ul><li>Morphology of teeth both primary and permanent </li></ul><ul><li>Terminology of key words </li></ul><ul><li>Masticatory movements and path of closure of the mandible </li></ul>
  3. 3. Definition of terms used <ul><li>Deciduous dentition </li></ul><ul><li>mixed dentition </li></ul><ul><li>Permanent dentition </li></ul><ul><li>Predecessor </li></ul><ul><li>Successor </li></ul>
  4. 4. Over bite <ul><li>Vertical distance between upper and lower incisal edges </li></ul>
  5. 5. Over jet <ul><li>Horizontal distance between upper and lower incisal edges. </li></ul>
  6. 6. Inclination of teeth <ul><li>Proclined </li></ul><ul><li>Vertical </li></ul><ul><li>Retroclined </li></ul>
  7. 7. Arch relationship
  8. 9. At birth - gum pads <ul><li>Upper horseshoe - shaped </li></ul><ul><li>Lower U - shaped </li></ul><ul><li>Covered with thick fibrous muco periosteum. </li></ul><ul><li>Contain 24 crypts of developing teeth. </li></ul><ul><li>Separated , tongue lies in between </li></ul>
  9. 11. Eruption of deciduous incisors. <ul><li>During the first year, the gum pads enlarge and arches widen to provide space for erupting incisors. </li></ul><ul><li>Timing of eruption 6 month variation </li></ul><ul><li>premature eruption of teeth natal and neonatal teeth. </li></ul>
  10. 12. Deciduous dentition <ul><li>Natal teeth </li></ul><ul><li>Neonatal teeth . </li></ul>
  11. 13. Sequence of eruption <ul><li>Lower central incisor </li></ul><ul><li>upper central incisor, </li></ul><ul><li>Lower lateral incisor </li></ul><ul><li>upper lateral incisor, </li></ul><ul><li>Lower primary first molar, </li></ul><ul><li>Upper primary first molar </li></ul><ul><li>Lower and upper primary canines </li></ul><ul><li>Lower and upper primary second molars. </li></ul>
  12. 15. Typical features of primary dentition <ul><li>Colour - whiter than permanent teeth </li></ul><ul><li>Size incisors and canines are smaller than permanent teeth </li></ul>
  13. 16. . Typical features of occlusion of primary dentition. <ul><li>Incisors are upright </li></ul><ul><li>Primate space present </li></ul><ul><li>positive over jet and over bite </li></ul><ul><li>each maxillary tooth occlude with two mandibular teeth. </li></ul><ul><li>Distal surfaces of primary second molars in same vertical plane. </li></ul>
  14. 20. Age changes from 3 to six years. <ul><li>Spacing begin to appear or existing spaces increase due to growth </li></ul><ul><li>occlusal attrition </li></ul><ul><li>incisor position become edge to edge </li></ul><ul><li>distal surfaces of second molar may not remain in same vertical plane </li></ul>
  15. 21. Development of occlusion <ul><li>Mixed dentition stage 6-12 years </li></ul>
  16. 22. Beginning of the mixed dentition <ul><li>Lower first molar erupt around six years. </li></ul>
  17. 27. Space gaining for incisor eruption <ul><li>Total size of lower primary incisors -17mm </li></ul><ul><li>Total size of lower permanent incisors -23mm </li></ul><ul><li>Upper primary incisors -23mm. </li></ul><ul><li>upper permanent incisors -30mm. </li></ul>
  18. 28. Space made available to accommodate incisors <ul><li>1. Spacing already present in th incisor region </li></ul><ul><li>2. increase of inter canine width </li></ul><ul><li>3.upper incisors erupt into wider arc </li></ul>
  19. 37. Leeway space <ul><li>Difference between total mesio -distal size of primary canine and both primary molars always larger than total size of permanent canine first premolar and second premolar. </li></ul><ul><li>C+D+E> 3+4+5 </li></ul><ul><li>Leeway space = (C+D+E )- (3+4+5) </li></ul>
  20. 43. Transient malocclusions seen in the mixed dentition <ul><ul><li>Transient incisor crowding </li></ul></ul>
  21. 44. Transient incisor crowding
  22. 48. Features of normal OCCLUSION <ul><li>Skeletal bases should be ideal </li></ul><ul><li>Correct size and correct relationship </li></ul>
  23. 52. Occlusal features <ul><li>All teeth are present and in correct contact with their immediate neighbors in the same arch with no spacing or rotations. </li></ul><ul><li>There is no tooth size disproportion between maxillary and mandibualr teeth. </li></ul><ul><li>The teeth are at correct inclination and angulation in their respective skeletal bases. Teeth of the buccal segment should be slightly mesially and lingually inclined and the teeth o f the labial segment should be slightly mesially inclined and proclined. </li></ul>
  24. 53. <ul><li>Each upper tooth occludes with corresponding tooth in the lower arch and one distal to it, with the exception of the upper third permanent molars. </li></ul><ul><li>Upper teeth lie labial or buccal to the lower teeth The lower labial segment teeth therefore, occlude with the palatal surface of the upper labial segment teeth and the buccal cusps of the lower buccal segment teeth occlude in the fossae of the upper buccal segment teeth. </li></ul>
  25. 54. <ul><li>Occlusal plane is slightly curved and can be considered to form a part of a sphere. The curvature in the sagittal plane is known as the Curve of Spee Curvature in the coronal plane is known as Curse of Monson. </li></ul><ul><li>The incisor, canine and molar relationship are class 1 </li></ul>
  26. 55. In function following observations are made, <ul><li>On protrusion there is incisal guidance where the incisors remain in contact with the buccal segment teeth out of occlusion. </li></ul><ul><li>In lateral excursions there is either canine guidance or group function in the buccal segments and there is no balancing or non working side interferences. </li></ul>
  27. 57. Occlusal features <ul><li>No rotations </li></ul><ul><li>No crowding or spacing </li></ul><ul><li>Correct inclinations </li></ul><ul><li>class I occlusion </li></ul><ul><li>occlusal plane has a slight curve </li></ul><ul><li>Curve of spee and Curve of Monson </li></ul>