tooth form and occlusion


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Introduction to Operative Dentistry
Third Year

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tooth form and occlusion

  1. 1.  Tooth form & Occlusion  
  2. 2.   Tooth form and occlusion Importance Determine: - Restoration of teeth: Generally, the restoration should mimic the original tooth anatomy to restore 1. efficient mastication, 2. esthetics, 3. speech and 4. protection of investing tissues
  3. 3.  Agenda  Physiology of tooth form How the structure of enamel and dentin influence cavity design? Features of an ideal occlusion Factors of occlusion affecting restorative  dentistry
  4. 4.  Physiology of tooth form  Contact area  Marginal ridge  Embrasure
  5. 5.  Normal periodontium • Restoration margin should be placed supragingivally to preserve the gingival health
  6. 6. Tooth contours   • Definition: convexity of axial surfaces of teeth • Function: Protection of supporting tissues Stimulation of gingiva during mastication
  7. 7.   Tooth contours  Over-contour - Food deflect during mastication with less stimulation of gingiva. - Food retention under overcontour with consequent caries or gingivitis  Under-contour - Direct impact of food on supporting tissues causing trauma to them.  Normal
  8. 8.  Height of epithelial attachment • The epithelial attachment seals the soft tissue to the tooth. • It could be injured during - Careless probing during examination. - Improper tooth preparation techniques. • Care should be taken during tooth preparation to avoid injury to periodontal attachment.
  9. 9.  Marginal ridges • In restorative dentistry, marginal ridges should be restored in two planes; buccolingually and cervico occlusally • Adjacent marginal ridges should be restored at the same height.
  10. 10.  Embrasure • The correct relationship of embrasures, cusp to sulci, marginal ridge and grooves of adjacent and opposite teeth provide for the escape of food from occlusal surfaces during mastication. • Correct embrasure form and size is important for self cleaning action.
  11. 11.  Proximal contact Definition: height of contour of the proximal surface of tooth that touches its adjacent tooth in  the same arch    Location: - Incisal 1/3 of incisors - Premolars and molars: Junction of occlusal and middle 1/3
  12. 12. How the structure of enamel and dentin influence tooth preparation? • Enamel - Enamel is brittle and when not supported by sound dentin [undermined enamel], it is liable to fracture and should be removed.
  13. 13. How the structure of enamel and dentin influence cavity design? • Dentin -Dentin is sensitive at dentino- enamel junction due to branching of dentinal tubules at that region. -Obstruction of dentinal tubules and precipitation of minerals by aging or due to subjection to irritation reduce dentin sensitivity. - Cavity floor should be o.20.5 mm beyond sensitive DEJ for non adhesive restoration..
  14. 14. Occlusion • Definition Occlusion means the contact of teeth in opposing dental arches when the jaws are closed (static occlusal relationships) and during various jaw movements (dynamic occlusal relationships)
  15. 15. Occlusion • Definition Centric relation is the relation between mandible and maxilla where the condyle in the rear most, upper and mid most position in the glenoid fossa.
  16. 16. Occlusion Definition • Maximum intercuspation is the maximum occlusal intercuspation irrespective of condylar position. • Complete intercuspation is seen when the intercuspal position and retruded position are coincident during mandibular closure. • Occlusal contacts that prevents this are called premature contacts
  17. 17. Angle’s classification for interarch relationship - Class I: most common [maxillary mesiofacial cusp located in the mesiofacial developmental groove of the mandibular first molar] - Class II: posterior positioning of mandible to maxilla. - Class III: anterior positioning of mandible to maxilla.
  18. 18.  Mandibular movement  Rotational movement around the horizontal axis.
  19. 19.  Mandibular movement Forward movement of the mandible [protrusion]
  20. 20.  Mandibular movement Side to side movement [lateral excursions] Working  side Balancing  side
  21. 21. Features of an ideal occlusion
  22. 22.  Inter-arch tooth relationship • The contact relationship is either 1- Surface contact [anterior] 2- Cusp to fossa apposition [posterior teeth]. Supporting  cusp    
  23. 23. Cusp to fossa relationship [cusp to  marginal ridge] • Supporting cusps are mandibular buccal cusps and maxillary palatal cusps
  24. 24.  Cusp to fossa relationship • Non Supporting cusps are mandibular lingual cusps and maxillary buccal cusps          
  25. 25.  Patient with cusp to fossa contact
  26. 26. Alignment of teeth and Dental arches   • In both jaws, cusps are aligned in parabolic curves. • In normal condition, maxillary jaw overlap mandibular jaw.
  27. 27.  References Chapter 4; physiology of  tooth form Chapter 2; clinical significance of dental anatomy, histology, physiology and occlusion