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Rest Seat And Rest Seat Preparation Presented by: Dr. Tushar Bhagat BDS, MDS (Prosthodontics) Diploma in Advance Implantology (Romania)
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Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

May 22, 2018

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Page 1: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Rest Seat And

Rest Seat PreparationPresented by:

Dr. Tushar Bhagat

BDS, MDS (Prosthodontics)

Diploma in Advance Implantology (Romania)

Page 2: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Content & References

2

• Definition of rest seat (B.p.no.67)

• Purpose of rest seat (B.p.no.67)

• Types of rest seat. Primary & Auxiliary Rest seat (A.p.no.44)

• Various forms of rest seat

– Occlusal rest & rest seat (Proximal RS, Long occlusal RS, Embrasure RS)

(A.p.no.44-47; B.p.no.68-71)

– Lingual or cingulum RS (Inverted “V” RS, Ledge RS, Ball RS) (A.p.no.47-48;

B.p.no. 76-78)

– Incisal RS (A.p.no.48-49)

• Re-contouring / Enameloplasty & Dimpling (Stewart’s-p.no.286)

• Definition

• Reasons for re-contouring

• Dimpling

Page 3: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Introduction

• Rest is a component of a direct RPD (direct &

indirect retainer).

• Rest designated by the surface of the tooth

prepared. (occlusal rest, incisal rest etc.)

3

lingual

buccal

Retentive arm

Bracing arm

Page 4: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Definition

• Rest: The component of RPD that transfer

forces down the long axis of the abutment teeth

are called as Rest.

4

Ref: Stewart’s Removable partial prosthodontics. P.n.43

Page 5: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Definition

• Rest seat: the prepared surface of teeth into

which rest fits are called as Rest Seat.

5

Ref: Stewart’s Removable partial prosthodontics. P.n.43

Lect.No.4. Abutment

teeth preparation.

Page 6: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Types of Rest Seat

1) The rest that is part of retentive clasp assembly is

referred as primary rest seat.

2) The rest that is additional support or indirect retainer

retention is called auxiliary rest or secondary rest.

6

Ref: Stewart’s Removable partial prosthodontics. P.n.44

auxiliary rest primary rest seat.

Page 7: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Primary rest seat

• Prevents vertical movements of prosthesis towards

tissues.

• Transmit applied forces to supporting teeth.

• Seat should be shallow & saucer shape so that it should

function like ball and socket joint

7

Ref: Stewart’s Removable partial prosthodontics. P.n.44

Page 8: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Auxiliary rest seat

• Used as indirect retainers in extension base RPD

(Class I, II & long span Class IV)

• Placed anteriorly or posteriorly to the axis of rotation to

prevent extension bases from lifting away from

underlying ridge.

8

Ref: Stewart’s Removable partial prosthodontics. P.n.44

Page 9: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Purpose of rest

1) Maintained component in planned position.

2) Maintain established occlusal relationship

by preventing settling of the denture.

9

Ref: McCraken Removable partial prosthodontics. P.n.67.

Page 10: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Purpose of rest

3) Prevent impinging of soft tissue.

4) Direct and distribute occlusal load to

abutment teeth.

10

Ref: McCraken Removable partial prosthodontics. P.n.67.

Page 11: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Function of rest seat

1) To maintain a planned clasp-tooth

relationship.

2) To prevent extrusion of abutment teeth.

11Lect.No.4. Abutment

teeth preparation.

Page 12: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Function of rest seat

3) To provide positive reference seats in

rebasing and/or impression procedures.

4) To serve as an indirect retainer by

preventing rotation of the partial denture

(Class I or II RPD’s only).

12Lect.No.4. Abutment

teeth preparation.

Page 13: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Criteria for preparation of rest

seat

High speed hand piece with coolant.

Light pressure while preparing seat.

Good visibility.

Preparation entirely in enamel, (better avoid

anaesthesia).

Medium round bur (diamond or carbide.)

13

Page 14: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Types of rest seat

A. Occlusal rest seat

B. Lingual / cingulum rest seat

C. Incisal rest seat

D. Intracoronal / precision rest

14

Ref: Stewart’s Removable partial prosthodontics. P.n.44

Page 15: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Posterior rest seat

I. Occlusal rest seat Proximal RS

II. Long occlusal rest seat

III. Embrasure rest seat

Page 16: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Posterior tooth rest seat form

• Rest should not be placed on

inadequately prepared tooth.

• Outline form is triangular with base

of triangle located at marginal

ridge & the rounded apex directed

toward the centre of tooth.

16

Ref: Stewart’s Removable partial prosthodontics. P.n.44

Page 17: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Posterior tooth rest seat form

• Shape should follow outline of

mesial or distal fossa.

• Should occupy 1/3rd to 1/2 the

mesiodistal diameter of tooth.

• And approx. ½ the buccolingual

width of the tooth measured from

cusp tip to tip. 17

Ref: Stewart’s Removable partial prosthodontics. P.n.45

Page 18: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Posterior tooth rest seat form

• The floor of the rest seat must

inclined slightly towards the centre

of tooth.

• Floor should be concave or saucer

shape.

18

Ref: Stewart’s Removable partial prosthodontics. P.n.45

Page 19: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Posterior tooth rest seat form

• The most common mistake

insufficient reduction of marginal

ridge.

• 1.0 – 1.5mm thick where it crosses

marginal ridge.

19

Ref: Stewart’s Removable partial prosthodontics. P.n.45

Page 20: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Proximal rest seat

• The preparation is at least 1.0 mm deep with a

slightly deeper portion (0.5 mm) called the

POSITIVE SEAT located toward the center of

the preparation.

20Lect.No.4. Abutment

teeth preparation.

Page 21: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Embrasure occlusal rest seat

• The EMBRASURE OCCLUSAL REST is

located in a fossa adjacent to another

tooth .

• Its size, shape and dimensions are

similar to the proximal occlusal rest

preparation EXCEPT that the flare of the

facial margin is limited by the proximal

contact with the adjacent tooth21

Page 22: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Long / extended occlusal rest seat

22Lect.No.4. Abutment

teeth preparation.

Page 23: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Anterior rest seat

Lingual / cingulum rest

•Preferable placed on maxillary canine.

Incisal rest

•Placed on anterior teeth.

23

Ref: Stewart’s Removable Prosthodontics. P.no.47

Page 24: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Lingual / cingulum rest

seat

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Placed on the lingual surface of maxillary

canines and incisors and in maxillary and

mandibular surveyed crowns.

Page 25: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Lingual / cingulum rest

seat

25

Rarely use on natural mandibular

incisors and canines because

there is usually insufficient

enamel thickness for an adequate

lingual rest preparation.

Page 26: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Lingual / cingulum rest

seat

26

Often requires for indirect retention.

Page 27: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Lingual / cingulum rest

seat

27

There are three types of lingual rest

preparations based on their shape:

Inverted V shaped

Ledge shaped

Ball rest seat

Page 28: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Inverted ‘V’ rest seat 28

This type of rest are made in canines and

incisors having a prominent cingulum.

They follows the contours of the cingulum.

Shape is usually ‘V’ when viewed from the

lingual.

Page 29: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Inverted ‘V’ rest seat 29

The floor of the inverted ‘V’

rest seat preparation is placed

in the bulk of the cingulum.

The floor is deepest toward the

center of the tooth thus

forming a positive faciolingual

seat.

Page 30: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Inverted ‘V’ rest seat 30

Preparation extends more cervically on

the mesial and distal thus forming a

positive mesiodistal seat.

The preparation extends through the

marginal ridges.

The cingulum shaped rest preparation

is approximately 1.0 mm deep pulpally

and cervically.

Page 31: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Ledge / Cingulum ledge

rest seat

Usually prepared on lingual

surface of maxillary anterior teeth.

Step like preparation from mesial

to distal.

The opposite ridge should not be

reduced.

31

Page 32: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Ledge / Cingulum ledge

rest seat

1.5 mm deep,

Should be perpendicular to the

long axis of the tooth,

Location at the junction of the

middle & gingival 3rd of the tooth.

32

Page 33: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Ledge / Cingulum ledge

rest seat No undercut on labial wall.

Sharp line angle should be avoided.

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Page 34: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Ball rest seat

Ball rest seat is preferable used as

auxiliary rest or indirect retainer.

It can be given in both maxillary &

mandibular anterior.

At the cingulum.

34

Page 35: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Ball rest seat 35

Page 36: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Anterior rest seat

Lingual / cingulum rest

• Inverted V

• Cingulum Ledge

• Ball rest seat

Incisal rest

• Placed on anterior teeth.

36

Page 37: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Incisal rest seat

Incisal rests are placed on the incisal edges of

mandibular incisors.

They are not placed on maxillary incisors

because the minor connector of the rest would

interfere with occlusion and the facial portion

of the rest would be very visible and

unaesthetic.

37

Page 38: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Incisal rest seat

Incisal rests are usually located in

the mesial or distal half of the tooth.

The rest should also be located so

that it will direct forces parallel to

the long axis of the tooth when

occlusal forces are applied to the

prosthetic teeth.

38

Page 39: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Incisal rest seat

The mesiodistal dimension of the rest

preparation should be 1.5 – 2.5 mm and the

depth at least 1 mm to provide adequate space

for a bulk of metal for the rest

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Page 40: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Guide plane preparation

Define as, two or more parallel, vertical surfaces of

abutment teeth, so shaped to direct the prosthesis

during placement & removal.

40

Ref: McCraken Removable Prosthodontics. P.no.155

Page 41: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Rule for Guide plane

preparation

Proximal guide plane surface should be 1/3 to 1/2

distance between buccal & lingual cusp.

Vertically minor connector contact enamel of tooth

on proximal surface about 2/3 its length.

41

1/3 to 1/2

Buccal

Lingual 2/3 its length

Page 42: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Function of Guide plane

I. To provide for one path of placement & removal

II. To ensure the intended action of reciprocal,

stabilizing & retentive components

III. To provide stabilization against horizontal rotation

of dentures.

IV. To eliminate gross food entraps between

abutment & component of RPD.

42

Ref: McCraken Removable Prosthodontics. P.no.155

Page 43: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Enameloplasty

Conservation must be rule when

doing recontouring enamel surface.

Used to create retentive undercuts

Term used as “Dimpling”

Depression approximately 4 mm MD

& length occlusogingival height

43

Ref: Stewart’s Removable Prosthodontics. P.no.286

Page 44: Rest Seat And Rest Seat Preparation - faculty.psau.edu.sa · indirect retainer). •Rest designated by the surface of the tooth ... lingual rest preparation. ... This type of rest

Thank You 44