Rest and rest seat

Question 1

Def ,Rest and rest seat

Answer 1

Rest → rigid metal projection attached to metal framework rest on occlusal or lingual or incisal of
teeth to resist vertical lodging force ( give support) ‘‘transfer force along long axis of abutment

Rest seat → prepared surface on tooth or fixed restoration where rest is placed.

Question 2

Function of rest

Answer 2

1-support → primary function by resist vertical lodging force ‘‘tissue ward movement of denture.
2-bracing → by resistance to lateral forces.
3-mentain retention: Maintain retentive clasp arm in its position.
4-act as indirect retainer: Used In free end saddle to resist rotational tissue away movement.

Question 3

Types of rests

Answer 3

1-occlusal rest

2-lingual / cinglum rest

3-incisal rest

Question 4

Requirements of rest seat and rest

Answer 4

1-outline form:
Is smooth rounded triangular, base at marginal ridge and apex toward centre of occlusal surface
2-dimension:
Mesiodistal (1/3;1/2 mesiodistal width), buccolingual (half distance from cusp tip to cusp tip or 2/3 of
width of marginal ridge)
3-depth:
Within enamel not extend to dentin, at marginal ridge 0.5mm and toward center of occlusal surface is
1;1.5 mm
4-floor inclined toward center of occlusal surface to direct force vertically with long axis of tooth.

Question 5

Types/forms of occlusal rests:

Answer 5

1-classical occlusal rest (as before)
2-extended occlusal rest, * indicated a-if can’t make adequate depth
3-double occlusal rest opposing each other on the same tooth
*indicated if can’t make adequate depth or extension

Question 6

-lingual / cinglum rest:
Teeth → most indicated on

Answer 6

maxillary canine

Question 7

advantages of cinglum rest over incisal rest:

Answer 7

1-mechanical advantage where it is near to center of rotation of the tooth so transfer force near to
center of the tooth.
2- esthetic advantage as it placed lingual. so avoid metal display.
shape rest seat :
Mesiodistal view → half moon or oval (crescent shape) (kidney shape)
Buccolingual view → V-shaped, deepest part toward center of the tooth

Question 8

incisal rest indications

Answer 8

1-when lingual / cinglum rest less desirable for anterior teeth
2-mandibular canine is the most preferred for incisal rest

Question 9

incisal rest V-shaped notch extend slight to facial surface type, preparation

Answer 9

preparation → Prefer at distal surface to avoid metal display