REST AND REST SEAT

Dr. Shaima’a Ahmed Radwan

Vertical forces acting in gingival direction tending to move the denture towards the tissues

• 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

auxiliary rest

(principle rest)

part of a clasp assembly

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

I. Occlusal Rest II- Lingual Rests III. Incisal Rest

RESTS

IV- Embrasure Hooks

I. Occlusal Rest

1.Conventional forms • 1- Should Be Rounded Triangular in Shape

• The Marginal Ridge Is Lowered Approximately 1 to 1.5 Mm of Teeth in Relation to a Vertical Line (permit sufficient bulk )

• Spoon Shaped Inclined Apically As It Approaches the Center of the Tooth

The floor of the rest seat should be spoon shaped(saucer)

-Rests , should be prepared in Sound Enamel

Rests , could be prepared in cast restorations, Crowns Or inlays

• Amalgam Restoration??????????????????????????

• It must not raise the vertical dimension of occlusion

2.Other forms

a. Boxed shaped occlusal rest

These rest seats should be restricted to tooth-supported dentures where the periodontal health of the abutment teeth is good. Helps in Preventing Lateral Movement of the Denture may result in the rest applying damaging horizontal loads on the abutment tooth.

B-Tipped molar(mesially inclined mandibular molar)

Extending the occlusal rest over the center of the mesio­distal fissure, directs the forces along the long axis of the tooth

B-Tipped molar(mesially inclined mandibular molar)

Additional occlusal rest Extended occlusal rest

C. ONLAY REST

Improve vertical dimension of occlusion splinting

D.Interproximal occlusal rest

E.Embrasure Rest

Rest seat distribution

Rest seat distribution

Gum striping in partial denture

II- Lingual Rests I- Occlusal Rest

III. Incisal Rest

Rests

IV- Embrasure Hooks

A- Cingulum Rest (inverted V Rest)

b. Canine Ledge

A Step-like Preparation 1.5 mm Deep

C. Ball Rest

1.5 Mm Deep - 2.5 Mm Wide

II- Lingual Rests

II- Lingual Rests I- Occlusal Rest

III. Incisal Rest

Rests

IV- Embrasure Hooks

III- Incisal Rest

Used Predominantly As Auxiliary Rests or As Indirect Retainers

-Applicable on Mandibular Teeth 2.5 Mm Wide and 1.5 mm Deep

LINGUAL VS INCISAL

The Lingual Placed Closer to the Center of Rotation of the Abutment Tooth

More Esthetic

Tongue

I. Occlusal Rest II- Lingual Rests III. Incisal Rest

RESTS

IV- Embrasure Hooks

IV- Embrasure Hooks

Placed in Embrasures Between Teeth Extending Over the B or Lab Surface but Never Extend Below S. L.