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Rests & Rest Seats. Rest A rigid component resting in a recessed preparation on the occlusal, lingual or incisal surface A rigid component resting in.

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Presentation on theme: "Rests & Rest Seats. Rest A rigid component resting in a recessed preparation on the occlusal, lingual or incisal surface A rigid component resting in."— Presentation transcript:

1 Rests & Rest Seats

2 Rest A rigid component resting in a recessed preparation on the occlusal, lingual or incisal surface A rigid component resting in a recessed preparation on the occlusal, lingual or incisal surface Provides vertical support Provides vertical support

3 Rest Seat Portion of a tooth prepared to receive a rest Portion of a tooth prepared to receive a rest

4 Intracoronal (Precision) Rest Precision manufactured attachments placed within a crown or retainer Precision manufactured attachments placed within a crown or retainer

5 Functions Direct forces along long axis of abutment Direct forces along long axis of abutment

6 Functions SUPPORT - prevents denture base from moving cervically & impinging gingiva SUPPORT - prevents denture base from moving cervically & impinging gingiva Slides down incline Fractured abutment, no rest seat

7 Major connector imbeds into tissue

8

9 Functions Maintain a clasp -tooth relationship Maintain a clasp -tooth relationship

10 Functions Prevent extrusion of abutments Prevent extrusion of abutments Provide reference for relines or impressions Provide reference for relines or impressions

11 Functions Act as indirect retainer Act as indirect retainer Prevents rotation (Class I or II RPD s only) Prevents rotation (Class I or II RPD s only)

12 Preparation of Rest Seats Light pressure Light pressure High-speed handpiece High-speed handpiece +/- Waterspray +/- Waterspray Minimal heat is generated Minimal heat is generated

13 Preparation of Rest Seats Keep in enamel Keep in enamel No anesthesia No anesthesia

14 Preparation of Rest Seats Occlusal Rest Seats Occlusal Rest Seats Diamonds Diamonds 8801- 014 8801- 014 38006 -135 38006 -135 8801- 014

15 Rest Seat Form Smooth flowing outline form (i.e. no sharp line angles) Smooth flowing outline form (i.e. no sharp line angles)

16 Occlusal Rest Seat Form Rounded triangular shape Rounded triangular shape Apex near center of tooth Apex near center of tooth

17 Occlusal Rest Seat Form Base of triangle should be one third the bucco-lingual width of the tooth Base of triangle should be one third the bucco-lingual width of the tooth

18 Occlusal Rest Seat Form Marginal ridge must be lowered and rounded 1-1.5mm Marginal ridge must be lowered and rounded 1-1.5mm Bulk of metal to prevent fracture Bulk of metal to prevent fracture

19 Occlusal Rest Seat Form Floor inclined towards the center Floor inclined towards the center Angle formed by rest and minor connector should be less than 90 0 Angle formed by rest and minor connector should be less than 90 0

20 Occlusal Rest Seat Form Deepest portion is central Deepest portion is central

21 Occlusal Rest Seat Form Floor should be concave or spoon shaped ball-&-socket joint Floor should be concave or spoon shaped ball-&-socket joint Prevents horizontal stresses & torque Prevents horizontal stresses & torque

22 Occlusal Rest Seat Form Directs the occlusal forces along the long axis of the tooth Directs the occlusal forces along the long axis of the tooth Prevent orthodontic movement Prevent orthodontic movement

23 Positive Rest Seats Positive Rest Seats Explorer tip will not slide off the rest seat Explorer tip will not slide off the rest seat

24 Avoid Undercuts Must draw along path of insertion Must draw along path of insertion

25 Occlusal Rest Seat Movie

26 Occlusal Rest Seat Form Conventional Form Conventional Form

27 Occlusal Rest Seat Form Adjacent Tooth Adjacent Tooth Rest not flared to facial line angle Rest not flared to facial line angle Lingual flared more - space for minor connector Lingual flared more - space for minor connector

28 Double Embrasure Rest Seat Form Adjacent teeth, the form is also modified Adjacent teeth, the form is also modified Flared more dramatically on facial and lingual line angles Flared more dramatically on facial and lingual line angles

29 Double Embrasure Rest Seat Form Provides space for the retentive & bracing arms Provides space for the retentive & bracing arms Ensure all line angles are smoothed Ensure all line angles are smoothed

30 Lingual Rest Seats Usually the canine, due to its well- developed cingulum Usually the canine, due to its well- developed cingulum When canine is not available, an incisor may be used When canine is not available, an incisor may be used

31 Cingulum Rest Seat Form Inverted V Inverted V < 90 0 < 90 0

32 Cingulum Rest Seat Form Slightly rounded to avoid sharp line angles Slightly rounded to avoid sharp line angles Test as positive with explorer tip Test as positive with explorer tip 1mm depth 1mm depth

33 Correct Preparation

34 Preparation Too High

35 Preparation Too Low

36 Preparation of Rest Seats Cingulum Rest Seats & Guiding Planes Cingulum Rest Seats & Guiding Planes Long, medium diameter cylindrical diamond 8837K-014 Long, medium diameter cylindrical diamond 8837K-014 8837K-014

37 Cingulum Rest Preparation Do not create an enamel undercut Do not create an enamel undercut Cylindrical bur along the long axis of the tooth Cylindrical bur along the long axis of the tooth

38 Cingulum Rest Seat Movie

39 Cingulum Rest Seat Placement Place in sound tooth structure or restorations Place in sound tooth structure or restorations Not on amalgam restorations Not on amalgam restorations If not prominent or large pulp If not prominent or large pulp Use different tooth Use different tooth Bonded rest seat Bonded rest seat Onlay or crown Onlay or crown

40 Maxillary Cingulum Rest Seats Avoid opposing occlusion Avoid opposing occlusion

41 Maxillary Cingulum Rest Seats 1.5 - 2.0 mm clearance for metal 1.5 - 2.0 mm clearance for metal Check with articulated models Check with articulated models

42 Bonded Cingulum Rests Flat emergence profile Flat emergence profile Pumice, rinse, etch, bond using rubber dam Pumice, rinse, etch, bond using rubber dam Ensure cervical composite well adapted Ensure cervical composite well adapted

43 Composite Bonded Rest Seat Form CorrectOvercontouredOvercontoured Open margin

44 Bonded Rest Seat Movie

45 Round Lingual Rest Seat Form Mesial of the canine teeth when typical cingulum rest contraindicated Mesial of the canine teeth when typical cingulum rest contraindicated Large restoration Large restoration Lack of clearance with the opposing teeth Lack of clearance with the opposing teeth Poor cingulum Poor cingulum

46 Round Lingual Rest Seat Form Spoon shaped, similar to occlusal rest seat Spoon shaped, similar to occlusal rest seat More difficult due to the incline of the lingual surface More difficult due to the incline of the lingual surface Easily incorporated into crowns Easily incorporated into crowns

47 Incisal Rests Inferior mechanically & esthetically Inferior mechanically & esthetically Lingual rest is nearer to the center of rotation Lingual rest is nearer to the center of rotation Less torquing potential Less torquing potential

48 Bring to Seminar Rooms: Ball burnisher if you have one Ball burnisher if you have one Boxof casts with prepartions on them Boxof casts with prepartions on them Any typodonts for checking of guiding plane preparations (Surveyor needed for checking) Any typodonts for checking of guiding plane preparations (Surveyor needed for checking)


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