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DSRP 6602/6603DISP 7212/7213

Lecture 2

Components, Tooth

modifications

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RPD Components

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RPD Components

Major Connectors

Minor ConnectorsProximal Plates

Rests

Direct RetainersIndirect Retainers

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Major Connectors

Connect parts of the prosthesis on one

side of the arch to those on the opposite

side

All other parts are directly or indirectly

attached to this component

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Major Connectors

Rigidity is necessary to

Control the relationship of remaining teeth to eachother, minimizing movement of the RPD

Control direction of force and torque against allremaining support structures & opposing occlusion

Provide greatest potential to control functional loadingby utilizing and uniting all remaining structures of thearch

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Maxillary

Major Connectors

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Maxillary Major Connectors

Considerations

Gingival tissue requires unrestricted superficial bloodsupply borders of MC should be minimum 6mm

away & parallel to gingival margins

The posterior limit for all maxillary MC shouldterminate just anterior to the vibrating line

All MC should cross midline at right angles, notdiagonally, for better tongue acceptance

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Maxillary Major Connectors

Types (4)

Full Palate Major Connector

Single Palatal Strap Major Connector

Anterior/Posterior Palatal Strap Major Connector

Horseshoe (U-shaped) Major Connector

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Uniformly thin, broad, contoured plate followingcontours of/covering the (majority of the) palate

Indicated in situations where remainingabutment tooth on either side is canine or 1stpremolar, esp. in cases with severe vertical ridgeresorption, complete denture scenario

It is thought to be more readily accepted byunderlying tissues and tongue because of closeadaptation to palate, thinness, & thermalconductivity

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Anterior/Posterior Strap

Major Connector

What does this remind you of?

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Anterior/Posterior Strap

Major Connector

Very stable & rigid MC- strength from A/P straps

linked by struts forming square frame, all

components brace others against possible

torque & flexureMX torus may be encircled by this MC

Can be used with any Kennedy Class

Posterior strap should be flat, at least 8mm wide,and located as far posteriorly as possible

anterior to vibrating line

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Single Palatal Strap

Major Connector

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Single Palatal Strap

Major Connector

Indicated for situations with bilateral tooth-support and posterior edentulous spaces(Kennedy Class III)

Sufficient rigidity = minimum 8mm width

Not indicated to connect anterior edentulousspace with distal extension bases, for thesecases use A-P strap

Preferred by patients over an A-P strap

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U-Shaped Major Connector

Horseshoe

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U-Shaped Major Connector

Least desirable of MC designs, should never be usedarbitrarily

Lacks rigidity, allows lateral flexure under occlusal loads,

leading to torquing to abutment teeth

Useful in Class IV RPDs

Primary indication is large inoperable torus, whichextends posteriorly, inhibiting placement of posteriorstrap

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Mandibular

Major Connectors

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Mandibular Major Connectors

Types (2)

Lingual Bar Major Connector

Linguoplate Major Connector

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Located above moving tissue (floor of themouth) and as far as possible below gingivaltissue margins

Superior border = 4mm below free gingivalmargin

Inferior aspect has half-pear contour for greatest

bulk & rigidity

Preferred by patients over a linguoplate

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Note: 8 mm requirement

vertically from FGM

to base of bar. Boards

require 7 mm minimum,

(3 gingiva, 4 bar).

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Note: 4+ mm rule

National boards: 3+ mm rule

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Superiorly should follow natural curvature

of tooth contour above cingula, not

extending above middle 1/3 of teeth

The linguoplate itself is NOT considered

an adequate indirect retainer. Must have

terminal rests or cingulum rests beneath

the plate in Kennedy Class I, IIs

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Indications

Stabilization of periodontally mobile teeth by

splinting

Provision for future anticipated loss of teeth

which may be added to the plate

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RPD Components

Major Connectors

Minor ConnectorsProximal Plates

Rests

Direct RetainersIndirect Retainers

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Minor Connectors

Connecting link from MC or denture baseto all other RPD components

Transfer stresses to abutment teeth and/orunderlying supporting tissues

Supports the clasp and rest assembly

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Minor Connectors

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Minor Connectors Retaining

Denture Bases

Ladder

Lattice Meshwork

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Minor Connectors

Open lattice or ladder design preferable

Should not interfere with setting of teeth

Mandibular distal extension should extend at

least 2/3 length of edentulous span

20 gauge wax relief between framework & basal

seat

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Guide Plane

A flat area on a tooth surface created tofollow the contour of the tooth and definethe path of insertion

Location: on the mesial &/or distal ofabutment teeth facing an edentulousspace

Size: 2-3 x 2-3 mm depending upon thetooth

Guide plate: the framework metal thatengages the guide plane

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Minor Connector: Proximal Plate

Proximal guide plate

in metal

Guide plane

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Minor Connectors:

proximal Guide Plates

Helps to maintain arch integrity by

anterior-posteriorbracing action

(resistance to horizontal forces)

Acts as a retainer (secondary) due to

frictional contact with parallel guiding

surfaces

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Guide Platesstability, support,

retention

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Minor Connectors: Rests are cast

to fit rest seats

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Rests & Rest Seats

Rests provide vertical support

Prevent impingement of soft tissues by

resisting tissue-ward movement

Direct & distribute occlusal loads tosupporting abutment teeth

Preserve established occlusal relationships

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Occlusal Rests & Rest Seats

Outline of rest seat should resemble rounded ,

with apex pointing toward center of tooth

Should be as long as it wide

At marginal ridge, base of should be at least

2.5mm for molars and premolars

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Height of marginal ridge should be

reduced at least 1.0-1.5 mm to allow for

bulk of metal for strength & rigidity

Floor of rest seat should be apical to

marginal ridge, spoon-shaped, concave

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Occlusal Rest Seats

Deepest part

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Rests & Rest Seats

Angle formed by occlusal rest and mC

from which it originates should be less

than 90 so that forces can be directed

down long axis of abutment tooth

If angle >90, slippage could occur and

orthodontic tooth movement may result

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Embrasure Rests

& Rest Seats

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Rest Seats

May be placed within sound enamel Enamel not at increased risk for caries given

appropriate oral hygiene

May be placed on any restorative materialscientifically proven to be fracture and distortionresistant

Important to inform pt ahead of time of thechance of perforation through existingrestoration, potentially necessitatingreplacement or repair (esp. crowns)

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Cingulum Rests & Rest Seats

Canine preferred over incisors

If lingual slope of chosen tooth is gradual

rather than perpendicular, bondedcomposite rest seat preferred

Cingulum rest preferred over incisal rest(less tendency to tip tooth and estheticallysuperior)

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Cingulum Rest Seats

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Incisal Rests & Rest Seats

Placed at incisal angles of anterior teeth

Least desirable placement of rest seat,

possible esthetic issue, may causeorthodontic movement due to unfavorableleverage

Rounded notch at incisal angle, withdeepest portion apical to incisal edge

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Single Incisal Rest

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Tooth Modifications for

RPD Designs

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Tooth modifications

Guide planes

Create an area of retention

Change of survey line (height of contour)

Rests

Survey crown

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Guide planes

Prepared on the mesial and/or distal ofabutment teeth aligned with the crest ofthe edentulous ridge

Extend from marginal ridge to junction ofmiddle and gingival thirds, dependingupon the contour of the tooth

NOT a meat cleaver slice, rather a gentlere-shaping of enamel which follows thecontour of the tooth, curved planes

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Distal guide plane #21

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Create an area of retention

This may be accomplished by

enameloplasty or composite resin bonding

Enameloplasty does not change the height

of contour when creating retention belowthe survey line

Composite resin bonding effectively

moves the survey line occlusally orincisally

#13: survey line too gingival,

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#13: survey line too gingival,

composite resin bonding indicated

facially to move retention occlusally

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Change in survey line

This may be accomplished by

enameloplasty or

composite resin bonding orsurvey crown

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Raising the survey line occlusally

increases retention below the line

Lowering the survey line gingivally

decreases retention below the line

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Remove interferences when seating the

retentive and reciprocal clasp arms or

guide planes (lowering the survey line)

NOTE: reciprocal arm must be in suprabulge

Enhance esthetics of clasp placement

(lowering the survey line)

Lowering survey line on disto

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Lowering survey line on disto-

facial of #21 for clasp placement

Remove interferences on mesial

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Remove interferences on mesial

of #25 & #29

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Rests

In enamel, NOT dentin (recurrent caries)

In existing amalgams, composite resins

In created composite resins

In survey crowns

In pre-existing crowns and FPDs, be

certain to obtain informed consent.why?

Occlusal rests mesial of

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Occlusal rests mesial of

#21(enamel) & #29(gold)

Composite resin cingulum rests

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Composite resin cingulum rests

to be bonded to #22, 27

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Survey crown

Why? When all else fails or the tooth would

be an excellent candidate for full coverage

in its own right

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FGSC #29 (the survey line is lousy)

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Occlusal view of survey crown #29

RPD 2008 Lec 2

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Transcript of RPD 2008 Lec 2