Rest & Rest Seat.ppt
- 1. Rests & Rest Seats
- 2. Rest A rigid component resting in a recessed preparation on the occlusal, lingual or incisal surface Provides vertical support
- 3. Rest Seat Portion of a tooth prepared to receive a rest
- 4. Functions Direct forces along long axis of abutment
- 5. Functions SUPPORT - prevents denture base from moving cervically & impinging gingiva Slides down incline Fractured abutment, no rest seat
- 6. Major connector imbeds into tissue
- 8. Functions Maintain a clasp -tooth relationship
- 9. Functions Prevent extrusion of abutments Provide reference for relines or impressions
- 10. Functions Act as indirect retainer Prevents rotation (Class I or II RPD’s only)
- 11. Preparation of Rest Seats Light pressure High-speed handpiece +/- Waterspray Minimal heat is generated
- 12. Preparation of Rest Seats Keep in enamel No anesthesia
- 13. Preparation of Rest Seats Occlusal Rest Seats Diamonds 8801- 014 38006 -135 8801- 014
- 14. Rest Seat Form Smooth flowing outline form (i.e. no sharp line angles)
- 15. Occlusal Rest Seat Form Rounded triangular shape Apex near center of tooth
- 16. Occlusal Rest Seat Form Base of triangle should be one third the bucco-lingual width of the tooth
- 17. Occlusal Rest Seat Form Marginal ridge must be lowered and rounded 1-1.5mm Bulk of metal to prevent fracture
- 18. Occlusal Rest Seat Form Floor inclined towards the center Angle formed by rest and minor connector should be less than 900
- 19. Occlusal Rest Seat Form Deepest portion is central
- 20. Occlusal Rest Seat Form Floor should be concave or spoon shaped ball-&-socket joint Prevents horizontal stresses & torque
- 21. Occlusal Rest Seat Form Directs the occlusal forces along the long axis of the tooth Prevent orthodontic movement
- 22. “Positive” Rest Seats Explorer tip will not slide off the rest seat Explorer will NOT slip off rest seat if pulled proximallly Explorer WILL slip off rest seat if pulled proximallly ‘Positive’ Rest Seat (< 90°) Rest Seat not ‘Positive’ (>90°)
- 23. Avoid Undercuts Must draw along path of insertion
- 24. Occlusal Rest Seat Movie
- 25. Occlusal Rest Seat Form Conventional Form
- 26. Occlusal Rest Seat Form Adjacent Tooth Rest not flared to facial line angle Lingual flared more - space for minor connector
- 27. Double Embrasure Rest Seat Form Adjacent teeth, the form is also modified Flared more dramatically on facial and lingual line angles
- 28. Double Embrasure Rest Seat Form Provides space for the retentive & bracing arms Ensure all line angles are smoothed
- 29. Lingual Rest Seats Usually the canine, due to its well- developed cingulum When canine is not available, an incisor may be used
- 30. Cingulum Rest Seat Form Inverted “V” < 900
- 31. Cingulum Rest Seat Form Slightly rounded to avoid sharp line angles Test as ‘positive’ with explorer tip 1mm depth
- 35. Preparation of Rest Seats Cingulum Rest Seats & Guiding Planes Long, medium diameter cylindrical diamond 8837K-014 8837K-014
- 36. Cingulum Rest Preparation Do not create an enamel undercut Cylindrical bur along the long axis of the tooth
- 37. Cingulum Rest Seat Movie
- 38. Cingulum Rest Seat Placement Place in sound tooth structure or restorations Not on amalgam restorations If not prominent or large pulp Use different tooth Bonded rest seat Onlay or crown
- 39. Maxillary Cingulum Rest Seats Avoid opposing occlusion
- 40. Maxillary Cingulum Rest Seats 1.5 - 2.0 mm clearance for metal Check with articulated models
- 41. Bonded Cingulum Rests Flat emergence profile Pumice, rinse, etch, bond using rubber dam Ensure cervical composite well adapted
- 42. Composite Bonded Rest Seat Form Correct Overcontoured Overcontoured Open margin
- 43. Bonded Rest Seat Movie
- 44. Round Lingual Rest Seat Form Mesial of the canine teeth when typical cingulum rest contraindicated Large restoration Lack of clearance with the opposing teeth Poor cingulum
- 45. Round Lingual Rest Seat Form Spoon shaped, similar to occlusal rest seat More difficult due to the incline of the lingual surface Easily incorporated into crowns
- 46. Incisal Rests Inferior mechanically & esthetically Lingual rest is nearer to the center of rotation Less torquing potential
- 47. Bring to Seminar Rooms: Ball burnisher if you have one Boxof casts with prepartions on them Any typodonts for checking of guiding plane preparations (Surveyor needed for checking)