Rests are rigid extensions of a partial denture that are placed in specially prepared rest seats on teeth. They provide support to the partial denture. There are three main types of rests: occlusal, incisal, and lingual. Occlusal rests contact the chewing surface and are the most common type. Incisal rests are placed on the front surface of teeth. Lingual rests are on the inside surface of teeth. Rests must be properly fitted, strong, not raise the bite, transmit forces down the long axis of the tooth, and secure the clasp in the right position. Well-made rest seats help control stresses on teeth.

1. ‫الرحيم‬ ‫الرحمن‬ ‫ال‬ ‫بسم‬

2. Occlusal Rests And Similar
Components

4. Definition
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

5. REST

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

7. The Prepared Recess in a
Tooth or Restoration Created
to Receive Occlusal, Incisal,
or Lingual Rest
Rest seat

9. Properly Prepared R.S. Help Control
Stress by Directing Forces
Transmitted to Abutment Teeth
Down the Long Axis of Those Teeth.
The Periodontal Ligament Is
Capable of Withstanding Vertical
Forces of Far Greater Magnitude
Than Off-vertical, (Near Horizontal)
or Torsional Force
Rest seat

10. Rests Are Either A Part Of A Clasp
Assembly Or An Auxiliary Rest
1- Occlusal Rest
2- Incisal Rest
Types of rests
3- Lingual Rest

12. Requirements
The rests must fulfill the following requirements:
1- They must fit the tooth ( minimize food collection and
preserve their location in relation to the tooth
2- they must be strong enough to withstand the loads
without deformation
3--they must not raise the vertical dimension of occlusion
4- ------------Transmit the stress with the long axis of the
tooth
5- they must be at right angle or less to the long axis of the
tooth

13. Fit- Strong-not Raise the Vertical Dimension

14. Not Raise the Vertical Dimension

15. Not Raise the
Vertical Dimension

17. 2-transmitting Vertical Stress Along the Long Axis of the Tooth
Functions:
6- It May Contributes to Indirect Retention
7- prevent ingress of food between the abutment and the
clasp
3-Secure the Clasp in Its Proper Position
4- Distributing the Occlusal Load
5- Resistance to Lateral Displacement of the Prosthesis
1-Support the denture against vertical forces ( PD without
rests called Gum stripper)

18. 1-Support

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

20. Secure the Clasp in Its
Proper Position

21. Distributing the Occlusal Load

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

24. 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
I- Occlusal Rest

25. 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.

26. REST SEAT
Apex Is
Directed
Towards the
Center
Rounded
Triangular
m
2.5 mm

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

28. 3- The floor of the rest
seat should be spoon
shaped

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

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

31. 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)

32. GUIDING PLANES

33. • Employed Only on a Perfectly
Periodontally Healthy Tooth
Special Considerations
• Provide Guide-surfaces
• Helps in Preventing
Lateral Movement of the
Denture
• It Provides Increased
Denture Retention
1- Boxed shaped occlusal rest

34. 2-Tipped Molar (Mesially
Inclined Mandibular Molar)

35. a- An Additional Occlusal Rest in the
Distal Fossa

36. b- Molar With Rest Preparation
Extended From Mesial Marginal Ridge
to Distal Triangular Fossa

37. c- A Casting Is Required, Such As Full
Veneer Crown or Onlay

38. c- A Casting Is Required, Such As Full
Veneer Crown or Onlay

39. 3- Interproximal Occlusal Rest
Seats

40. 4- Internal Rest (the Milled Rest, the
Semiprecision Attachment)

41. 5- Embrasure Rest
A Gap Between Two Molars

42. 5- Embrasure Rest
One Simple Circle Clasps Jointed Together, and the Rest
Recesses Should Be Fashioned on the Two Abutment Teeth

43. Two Simple Circle Clasps Jointed Together, and
the Occlusal Rest Can Be Used to Bridge a Gap
Between Teeth

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

47. A- Cingulum Rest
(inverted V Rest)

48. LabLing
M D
2 mm
1- 1.5 mm
Half -Moon Shaped V- Shaped
A

51. Adequate
Tooth
Preparation
Directs
Forces
Down Long
Axis of
Tooth

54. B. Ball Rest
No sharp line angles
1.5 Mm Deep - 2.5 Mm Wide

55. C. Canine Ledge
1.5 mm Deep
No Sharp Line Angles
A Step-like Preparation

56. III- Incisal Rest seatIII- Incisal Rest seat
1.5mm
2mm

57. 2mm
1.5mm

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

60. Used Predominantly As Auxiliary
Rests or As Indirect Retainers

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

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 B or Lab Surface
but Never Extend Below S. L.

65. IV- Embrasure Hooks
• Act As Indirect Retainer
•Resistance to Lateral
and Anteroposterior
Movement
•Splinting of Natural
Teeth
•Support

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

67. Onlays:
a restoration that restore the intire occlusal
surface
They are enlarged occlusal rests covering the
whole occlusal surface and extending buccally
and lingually
Indication:
1- increase the reduced VD
2- Reduce cusp angle
3-Improve balanced articulation

68. THANK YOU