2. RESTS AND REST SEATS

3. The Component Parts of Removable Partial Dentures
Denture Base
Artificial Teeth
Supporting Rests
Connectors: Major Connectors
Minor Connectors
Retainers
Direct retainers
Indirect Retainers

6. Clasp assembly

7. REST

8. Rests: - Are rigid extensions of a Partial Denture, Placed in Rest Seats, Which are prepared on either the Occlusal, Lingual surfaces or Incisal edges of the teeth, providing Support to the Partial Denture

10. Support
The Quality of the Prosthesis to Resist Displacement Towards Denture Supporting Structures

11. Functions Of The Rests Support
Transmitting vertical stress along the long axis of the tooth
Secure the clasp in its proper position
Distributing the Occlusal Load
It May Act As Indirect Retention.

12. SUPPORT & FORCE TRANSMISSION

13. Transmitting Vertical Stress Along The Long Axis Of The Tooth

14. 3-Secure the clasp arms in their proper position

15. Secure the Clasp in Its Proper Position

16. 4-Distributing the Occlusal Load

17. 5-May Act As Indirect Retention

19. 6-Restore occlusion of the abutment that show tilting or infra-occlusion (overlay rest)

20. Tipped molar (Mesially inclined mandibular molar)

21. Onlay (reduce cusp angle)

22. 7-Direct food away from tooth contact and embrasure area

23. A Gap Between Two Molars
Embrasure Rest
A Gap Between Two Molars

26. 8-Resistance to Lateral Displacement of the Prosthesis but applying damaging horizontal forces on abutment teeth

27. A- Rests are either a part of a Clasp Assembly (primary rest)
Types of rests:-
A- Rests are either a part of a Clasp Assembly (primary rest) Or
An Auxiliary Rest

28. Clasp assembly

29. Auxiliary rest

30. B-According to the relations to edentulous span: -
Adjacent to the saddle
Away from the saddle

31. C- According to positions: -
Occlusal rest{ molars- premolar}
Lingual rests{ cingulam of canines-or casted lingual restorations}
Incisal rests {canines-incisors}

32. I- Occlusal Rest
A Rigid Extension of a RPD That Contacts the Occlusal Surface of a Posterior Tooth or Restoration, on a Rest Seat Specially Prepared to Receive it.

33. Forms and Requirements of Rest Seat Preparation
1- Should Be Rounded Triangular in Shape the Base of the Triangle at the Marginal Ridge About 2.5 mm in Width, and Its Rounded Apex Is Directed Towards the Center of the Tooth
2.5m.m.

34. Rest Seat
1mm
2-The Marginal Ridge Is Lowered Approximately 1 to 1.5 Mm of Teeth in Relation to a Vertical Line (permit sufficient bulk )

35. 3- The floor of the rest seat should be spoon shaped

36. Forms and Requirements of Rest Seat Preparation
4- The angle between the minor connector and the rest should be less than 90˚
Prevent Slippage of the Prosthesis Creating an Orthodontic Like Force
To Direct the Forces Along the Long Axis of the Tooth

37. Rest Seat
1mm
4- Spoon Shaped Inclined Apically As It Approaches the Center of the Tooth

39. Forms And Requirements Of Rest Seat Preparation
5-Rest seats are prepared in sound enamel, existing restorations or in crowns and inlays
6-If an amalgam restoration is present, it could be replaced by a cast restoration (Occlusal rests can be prepared in an old amalgam restoration
7-Preparations for the occlusal rest must precede making master cast and follow proximal preparation (guiding planes and elimination of undesirable undercuts)

40. GUIDING PLANES

42. Requirements of the Occlusal Rest
I-O.R. must fit the tooth ( minimize food collection and preserve their location in relation to the tooth
2- It must be strong enough to withstand the loads without deform
3-It must not raise the vertical dimension of occlusion

45. Not Raise the Vertical Dimension

47. Special Considerations
1- Boxed shaped occlusal rest
Employed Only on a Perfectly Periodontally Healthy Tooth
Helps in Preventing Lateral Movement of the Denture

49. Rests
I- Occlusal Rest
II- Lingual Rests
III. Incisal Rest

50. II-Lingual Rests A- Cingulum Rest (inverted V Rest) B. Ball Rest
C. Canine Ledge

51. II-Lingual Rests A- Cingulum C. Canine Ledge B. Ball Rest
Rest ( V Rest)
B. Ball Rest

52. Half -Moon Shaped
V- Shaped
Lab
Ling D M
2 mm mm A

55. Adequate Tooth Preparation Directs Forces Down the Long Axis of Tooth

57. III- Incisal Rest seat
2mm
1.5mm

58. 2mm
1.5mm

59. III- Incisal Rest Rigid Extension More Applicable on Mandibular Teeth
Used Predominantly As Auxiliary Rests or As Indirect Retainers
2.5 mm Wide and 1.5 mm Deep

61. The Lingual Rest Is Preferable to an Incisal Rest
Placed Closer to the Center of Rotation of the Abutment Tooth
More Esthetic
Less Bothersome to a Curious Tongue

62. Lingual Rest Will Exert Less Leverage and Reducing Its Tendency to Tipping

63. Post Is More Readily Removed by Application of Force Near Its Top Than by Applying Same Force Nearer Ground Level

64. IV- Embrasure Hooks
Placed in Embrasures Between Teeth Extending Over the Buccal or Labial Surface but Never Extend Below Survey Line.

65. IV- Embrasure Hooks Resistance to Lateral and Anteroposterior Movement
Act As Indirect Retainer

66. IV- Embrasure Hooks
Poor Esthetics and Wedging Action on Teeth

67. THANK YOU