Rest And Rest Seat

Question 1

What is the definition of the rest

Answer 1

It is a rigid extension of partial denture which rests on occlusal , incisal, and lingual surface of a tooth to provide vertical support for removable partial denture and transmit functional forces to the teeth in an atraumatic fashion
Transfer forces down the long axis of the abutment teeth in this manner the stresses can be absorbed by the fibers of the PDL.

Question 2

Rest seats

Answer 2

The prepared surface of the teeth into which rests fit.

Question 3

10 functions of rests in partial denture

Answer 3

1- the primary purpose of the rest is to provide vertical support for the partial denture.
2- directs and distributes occlusal loads to the abutment teeth.
3- maintain components in their planned position.
4- maintains established occlusal relationships
5- prevents impingement of soft tissue.
6- serve as a reference point for evaluating the fit of the frame work to the tooth.
7- prevents extrusion, tipping,or migration of the abutment teeth.
8- acts along with its minor connector as an indirect retainer for a tooth tissue supported removable partial denture.
9- deflection of food by bridging the gap between two teeth
10- splints mobile teeth

Question 4

Primary rest

Answer 4

Prevent vertical movement of a prothesis toward the tissues and also help transmit applied forces to the supporting teeth.

Question 5

Secondary rests

Answer 5

Used as an indirect retainer in extension base removable partial denture class 1 ,2
Class 4 long span
وطبعا لازم الحروف بتاعهم يكتبو بالاتينى

Question 6

Three major forms of rests

Answer 6

1- occlusal rests
2- lingual or cinglum rests
3- incisal rests

Question 7

Primary rest

Answer 7

A rest that is a part of a retentive clasp

Question 8

What are the functional elements of the clasp

Answer 8

Reciprocal arm
Occlusal rest
Retentive arm
Minor connector

Question 9

Secondary rest or auxiliary rest

Answer 9

A rest is responsible for additional support or indirect retention.

Question 10

Three major forms of rests are

Answer 10

1- occlusal rests : seated on the occlusal surface of posterior teeth.
2- lingual or cinglum rests : seated on the lingual surfaces of anterior teeth , usually canines.
3- incisal rests : those seated on the incisal edges of anterior teeth.

Question 11

Give reason for the rest the seats should be shallow and saucer shaped and should function as ball and socket joints?

Answer 11

This geometry permits dissipation of potentially harmful lateral forces.

Question 12

Basic requirements of rest and rest seat

Answer 12

1- provide rigid support.
2- extends to the center of the tooth in tooth supported situations , so the vertical stress will be resisted by all of the periodontal ligament fibers.
3- no undercuts in the path of insertion.
4- minimum of 1 mm thick.
5- restore the occlusal plane.
6- contoured so that when increased force is applied to the prosthesis the rest will engage more securely to prevent separation
7- the floor of the rest seat should be less than 90 degrees to the long axis of the tooth to direct stresses axially, also its seat should be apical to the marginal ridge with no sharp angles. For ease of cleaning and prevent tooth fracture.