1) Denture base2) Artificial teeth3) Connectors4) Retainers5) Supporting rest

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Rest:Rest: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

Rest seat:Rest seat:portion of a tooth prepared to receive a rest

Functions Of The RestsFunctions Of The Rests1-Support(the main function):resist displacement towards denture supporting structures which will prevent impingement of gingival tissues adjacent to the abutment

2-maintain the components of the dentures in their positions and prevents spreading of clasp arm

3-Distributing the Occlusal Load

4-May Act As Indirect Retention

4-Direct food away from tooth contact and embrasure area

5- improve the existing occlusion

Types of restTypes of resti. Occlusal rest{ molars- premolar}

ii. Lingual rests{ cingulam of canines}

iii. Incisal rests {canines-incisors}

iv. Embrasure Hooks

A rigid extension of a RPD that contacts the occlusal surface of a posterior tooth or restoration,a rest seat specially prepared to receive it.

A-Occlusal RestA-Occlusal Rest

Types of occlusalTypes of occlusal restrest A- conventional

B-other forms: 1. Box-shaped O.R.2. Extended O.R.3. Onlay O.R.4. Inter proximal O.R.5. Embrasures O.R. 6. Internal O.R.

Partial denture without occlusal

rest is called gum stripper

Requirements of Rest Seat Requirements of Rest Seat PreparationPreparation

1- Should be rounded triangular outline form, the base of the triangle at the marginal ridge and its rounded apex is towards the center of the tooth

2-The marginal ridge is lowered approximately 1.5 mm for base metal alloy (permit sufficient bulk (

Mesiodistally from 1/3 to ½ Buccolingually ½ the distance between cusp tips

3-The angle between the minor connector and the rest should be less than 90˚

1- To prevent Slippage of the Prosthesis Creating an Orthodontic Like Force

2- To direct the forces Along the Long Axis of the tooth

4-the rest seat may be papered in either saucer shape or box shape Saucer shape(spoon) used more than box in cases of :•free end saddle •bounded cases having weak abutments

5-Rest seats are prepared in sound enamel, or in crowns and inlaysFluride gel applied to abutment

Requirements of occlusal RestRequirements of occlusal Rest::1.Should have sufficient thickness

of metal to prevent breakage especially over the marginal ridge.

2.It should fit the rest seat accurately with beveled margins, preventing food stagnation or impaction.

3.It must not raise the vertical dimensions of occlusion

4-In bounded partial denture: placed in the near zone of the occlusal surface to edentulous area

In free end partial dentures: placed in the far zone of the occlusal surface to decrease torque action on abutment tooth

use of amalgam restoration to

support an occlusal rest is less due to its tendency to creep and f low under pressure

B-other formsB-other forms1-Box shape1-Box shape

Indication a cast gold restorationsa strong periodontally healthy abutment a

Advantage

1.If made deep it will provide guide surfaces to control the path of insertion of the dentures 2.Prevent lateral movement of denture

3.Provide increased denture retention

2-Tipped molar2-Tipped molar(Mesially inclined mandibular molar)

•The rest should be designed to prevent further tipping, It must direct forces down the long axis of the tooth by either of one of these ways :

1. Additional occlusal rest in distal fossa

2. A rest preparation that extended from the mesial marginal ridge to the distal triangular fossa to minimize further tipping

box shaped less used in

bounded cases

33--onlayonlay

•An enlarged occlusal rest covering the entire occlusal surface and extending buccally and lingually •Retained by mechanical or adhesive means .

Functions : 1- support ( resist tissue award force (

2- improvement of occlusion by increasing the reduced vertical dimension ( correction of occlusion bite (

3- minimize lateral component of the force 4 - splinting ( in case of periodontally weak teeth (

Advantages : 1-direct the force along the long axis

2- promote RPD stability 3- minimize tipping of tooth

3-restore occlusal plane

3-interproximal O.R.3-interproximal O.R.•They are prepared as individual occlusal rest seats , except that the preparations must be extended further lingually than the ordinarily accomplished . • used to avoid interproximal wedging , additionally will shunt food away from contact points

Preparation : 1- should avoid weakening or eliminating contact points

2- provide adequate bulk for strength .3- occlusion should not be altered

Onlay Cast in gold or chrome

cobalt

44--EmbrasureEmbrasure restrestTwo simple circle clasps joined together fashioned on

the two abutment teeth .

Functions: 1- bridge gap between teeth

2- prevent food impaction between the space teeth

55--Internal restInternal restIndicated for bounded partial denture that totally tooth supported

Advantage: 1- support come from floor of the rest 2-Lateral stabilization from parallel wall

3-Retention from lingual clasp4-esthetics( buccal clasp (

II- Lingual RestsII- Lingual Rests : :

A- Cingulum Rest ( inverted V Rest (.B- Ball Rest.C- Canine Ledge.

A- Cingulam Rest A- Cingulam Rest (inverted Rest(inverted Rest((Def. a portion of RPD ; placed in an enamel seat at the

cingulam or just Incisal to it . Indication:

•no posterior tooth to place an occlusal rest .•commonly used on the maxillary canines•Rarely on lower anterior; due to less thickness of enamel

** the most satisfactory preparation is that placed on a prepared seat in a cast

restoration .

**when preparing a cingulam rest in a cast restoration ; the rest seat should be planned and done on the wax pattern before

casting the restoration .

Specification of Cingulum Rest Seat :1- A rounded inverted V shaped preparation

)half – moon shaped(.

2- All sharp angles & undercuts should be eliminated .3- The rest seat is broadest at the center and merges

as it approaches proximal surfaces

B- Canine ledgeB- Canine ledge : : - A step-like preparation ; placed on the mesial or distal

halves of the lingual surfaces of the maxillary canine .- The ledge rest seat should be perpendicular to the

long axis of the tooth .- All undercuts & sharp line angles should be avoided .

C- Ball RestC- Ball Rest : :Def: cingulam ball rests with rounded outline; placed on the mesial or distal halves on the lingual surfaces of all anterior teeth.

- BALL rest permits rotational movements to occur during function of tooth-mucosa born RPDs .

III- Incisal RestIII- Incisal Rest : : Def.: a rigid extension of a RPD , placed at the Incisal angles of anterior teeth on prepared rest seats.

- commonly used as auxiliary rest or as indirect retainers .

- More applicable on mandibular teeth due to lack of adequate thickness of enamel on the lingual surface.

- A saddle shaped preparation , and the notch should extend onto the facial surface to prevent the tooth

from moving labially .

N.B.:The lingual Rest is preferable to an incisal Rest ??

because:1.- placed closer to the center of rotation of the abutment, thus reducing its tendency to tipping 2.- More esthetic .3.- Less bothersome to tongue .

IV- Embrasure HooksIV- Embrasure Hooks : :

Def.: rests placed in embrasures between natural teeth extending slightly over the buccal or labial surface but

never extend below the survey line .

Advantages : - provide support .

- splinting of natural teeth .- resistance to lateral and antero-posterior movement .

- may act as indirect retainer .

Disadvantages :- poor esthetics .

- wedging action on teeth .

preferred site for a rest , is the occlusal

surface of a molar If anterior tooth , a

canine is preferred over an incisor

In absence of canine , multiple lingual rests are

prepared on anterior teeth .

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