Rests and rest seats are components of partial dentures that provide vertical support. A rest is a prepared surface on a tooth that supports the denture, while a rest seat is the prepared surface that receives the rest. There are different types of rests including occlusal, lingual, and incisal rests. An occlusal rest is triangular in shape with a rounded apex and a base of at least 2.5mm. The floor of the occlusal rest seat is concave and apical to the marginal ridge. Internal occlusal rests eliminate visible clasps and position the rest seat in a favorable location for support and stabilization. Lingual rests are prepared on the canines or incisors as a slightly

1. RESTS
AND
REST SEATS
Dr.Ajay

2. Definition:
REST: A component of a partial denture on a
tooth surface that provides vertical support is called a
rest
REST SEAT : Prepared surface of an abutment to
receive the rest is called rest seat

3.  Primary use-vertical support
 0ther uses
-Maintain components in planned positions
- Prevent settling of the denture
- Prevents impingement
-Distributes occlusal load to abutment

4. TYPES
Occlusal cingulum incisal
rest rest rest

5. OCCLUSAL REST AND REST SEAT:
 Outline form-rounded triangular shape with apex
towards center of occlusal surface
 Base of triangular shape should be atleast 2.5mm
both molars and premolars
 The reduction of marginal ridge of approximately
1.5mm is necessary

6.  Floor of rest seat-apical to marginal ridge and
occlusal surface and concave or spoon shaped
 The angle formed by the occlusal rest and the vertical
minor connector from which it originates should be
less than 90 degree

7. EXTENDED OCCLUSAL RESTS:
 Used in posterior most mesially tipped molars
 In Kennedy’s class II,modification 1 and kennedy
III
 Rest should extend morethan one half of mesio
diameter of tooth and one-third the buccolingual
width

8.  In severely tilted abutments-the extended occlusal
rest may take form of an onlay to restore occlusal
plane

9. INTERPROXIMAL OCCLUAL REST SEATS:
 The design of direct retainer may require this rest
 Prepared as individual occlusal rest seats with the
exception that the preparation must be extended
farther lingually
 Used to prevent interproximal wedging by the
framework

10.  In addition the joined rests are designed to shunt
food away from contact points
 Analysis of mounted casts is mandatory in this type
of rest

11. INTERNAL OCCLUSAL RESTS:
 A partial denture that is totally tooth supported by
means of cast retainers may use this for both
support and horizontal stabilization
Occlusal support-floor of rest seat
Horizontal stabilization –from near vertical walls
of rest seat

12.  Main advantage-eliminates visible clasp arm buccally
and permits the location of the rest seat in a more
favourable position in relation to tipping axis of the
abutment
 Only indication-tooth supported dentures

13. Lingual rests on canines and incisor teeth:
A canine is much preferred over an incisor for this
purpose, if canine is absent multiple incisor rests are
used
 PREPARATION:
Slightly rounded v is prepared at the junction of
gingival and middle third of tooth

14.  Apex of v is directed incisally
 Prepared by using an inverted cone shaped diamond
stone and progressing to smaller,tapered stones with
round ends
 Floor of rest seat:towards cingulum

15. INCISAL RESTS AND REST SEATS:
 Placed on incisal angles of anterior teeth
 It is least desirable and can be used selectively when
abutment is sound and cast restoration is othertwise
not indicated
 Used predominantly as auxillary rests or as indirect
retainers

16.  Preparation:
 Prepared in the form of a rounded notch at the
incisal angle with deepest portion apical to incisal
edge
 Should be approximately 2.5mm wide and 1.5 mm
deep

17. Reference:
McCracken’s removable partial denture
Stewart’s removable partial prosthodontics