L4 Components of RPD Pt 3

Question 1

Rests

Answer 1

a rigid extension of a partial denture which contacts a remaining tooth in a prepared rest seat to transmit vertical and horizontal forces

Question 2

What are the requirements of rests?

Answer 2

thickness, direct forces, sufficiently extended, rest seats

Question 3

What are the types of rests?

Answer 3

Occlusal Rest
- conventional 
- extended
- overlay
Incisal Rest
Lingual Rest
- cingulum
- ball

Question 4

Conventional occlusal rest design and measurements

Answer 4

• rounded triangular outline when viewed from occlusal
• smooth and rounded tissue surface
• should be 1/3 the F-L width of the tooth or 1/2 the width of the tooth measured at the cusp
• marginal ridges should be reduced to 1.5mm (base metal) and 2.0mm (gold)
• floor of the rest seat prep should be spoon shaped and inclined apically as it approaches the center of the tooth
• the angle between the minor connector and the rest should be less than 90deg.
• rests for embrasure clasps are formed by two adjacent occlusal rests

Question 5

Extending occlusal rest

Answer 5

For a tooth borne RPD, rests may be carried more than half way across the occlusal surface to promote axial force direction.
For tipped teeth, extended occlusal rests should minimize further tipping, and should direct loads along the long axis of the tooth.

Buccal and lingual dovetail extensions of the rest help to minimize movement of the teeth. This contributes to the encirclement.

Question 6

Overlay occlusal rest

Answer 6

Some abutment teeth require the restoration of their occlusal surface by the RPD. Occlusion is rested with a metal occlusal overall as part of the RPD framework.

• may contact O, F, L, and proximal surfaces
• mainly indicated for restoring the occlusal plane and resisting further tipping of the abutment tooth
• overlay rests may eliminate the need for cast restoration on abutment teeth

Question 7

Ball shaped lingual rest

Answer 7

• ball shaped rest seat with rounded outline
• placed on M or D half of the tooth usually at the junction btw the middle and gingival thirds
• ball shape permits rotational movements to occur during function of tooth-mucosa borne RPD.

Question 8

Indirect retainer design considerations..

Answer 8

..

Question 9

resin-metal base indications

Answer 9

1. extension bases in tooth-mucosa borne RPD
2. long span tooth borne basses
3. restoration of anatomic contour and esthetics
4. anticipated need to reline or adjust the base