8/10/2019 Qi 27 8 Zuckerman 13

1/6

Prosthodontics

Abstract

fVhen the abtttment

teeth

of a fixed partial

denture are severely

mlmligned

insertion

ofthe pmsthesis

becotnes tnoredifficult

Some ofthe tnethods

traditionally recomtnended to overcome the probletns associated with this situation

are examitied Otiedes ign that simplifiestreatmentandimproves the prosthesis is

suggested (Quintessence hit

1996:27:527-532.

Clinical relevance

A segmented fixed partial denture design with an

extracoronal interlocking attachment made from

prefabricated plastic patterns is tnore esthetic and

requires less tooth reduction than do traditional

designs recommended for ftxed partial dentures on

severely misaligned abutments.

to

be

replaced after the second and third molars have

).

raditional procedures

11731.

commit the time and funds necessary for this extended

and extensive treatment, requiring the coordinated

services of an orthodontist and a restorative dentist.

A Itered patho finsertion

It is possible to prepare the m olar abutment with a path

of insertion that is compatible with the premolar prep-

aration, but this approach has several disadvantages.

The retention and resistance of the molar prepared

under these conditions are severely compromised,-"'*

and the risk of creating a mechanical exposure ofthe

mesial pulp horn ofthe molar is increased. Further-

more, the mesial marginai ridge ofthe third molar, if

present, would interfere with insertion ofthe prosthe-

sis (Fig 2).

Mesial

half-crown retainer

Rosenstiel et a and Shillingburg et a i- have recom-

mended the use ofthe mesial half crown as a retainer

for tilted molars (Fig 3). A mesial half-crown retainer

has several disadvantages:

1.

The mesial half crown cannot be used if the molar

has previously been restored on the distal surface.

2.

Preparation ofthe molar could resuit in exposure of

the mesial pulp horn.

3.

The patient may object to the use of a cast-metal

restoration.

4.

Caries occurring on the unrestorcd distai surface of

the second molar abutment after insertion ofthe

prosthesis jeopardizes the restoration.

Shillingburg et al- have suggested use of a complete

coping with retentive grooves and a teiescopic mesial

halfcrown for the molar retainer {Fig 4 ). A retainer of

this design requires more tooth reduction and could

ce International Volume 27 Number 8 /t 99 6

527

8/10/2019 Qi 27 8 Zuckerman 13

2/6

Fig 1 The missing mandibular first molar has allowed

second and third molars to tilt mesially. Note the severe

misalignment between the long axes of the second pre-

molar A) and the second molar B),

Fig 2 Three-unit FPD with rigid connecto rs. The prosttie-

sis will not seat because the distal margin of the molar

retainer engages the mesial marginal ridge of the third

molar during insertion. Note the proxim ityof the mesial pulp

horn to the mesial axial wall of the molar preparation.

Fig 3 Three-unit FPD with rigid connectors. The second

molar abutment has been prepared for a mesial half-crown

retainer with facial and lingual grooves for added retention.

Note the proximity of the mesial pulp horn to the mesial axial

wall of the molar preparation.

Fig 4 fr/gh Three-unitFP with full coping and telescopic

mesial half crown on the molar abutment.

result in pulpal exposure or an overcontoured retainer.

Preparation of the tooth for the complete-coverage

coping would be excessively tapered. Even if retention

between the mesial half crown and the coping were

ideal, retention ofthe coping to the abutment tooth

might fail because of the excessively tapered tooth

preparation,^-^

Segmented FP

The use of a segmented F PD , in which each section of

the prosthesis has its own path of insertion and there is

a mechanical interlock between segments, has been

advocated. The literature contains a variety of seg-

mented prosthetic designs recommended to overcome

the problems associated with insertion of an FPD

when the abutments are divergent,

Shillingburg et a|- have suggested th e use of a

segmented FPD with a nonrigid attachment between

the second premolar retainer and pontic. This design

requires tooth prep aration o fth e premolar with a box

on the distal surface to accommodate the female

com ponen t of a nonrigid con nec tor Fig 5), Tooth

preparation of the premolar to accomrnodate this

connector could jeopardize the pulp and the retentive

528

Quintessence International Volume 27, Numb er 8/1996

8/10/2019 Qi 27 8 Zuckerman 13

3/6

g 5 Segmented FPD witb nonrigid connector between Fig 6 Segmented FPD with an interlock between the

second molar retainer and the ponfic. Excessive tooth

reduction is required on the mesial surface of fhe second

molar abutment to accommodate the female portion of fhe

interlock.

rface o fthe anterior retainer and can be cosmetically

O'Co nnor et a have proposed a segmented FP D

nonrigid conn ecto r is oriented parallel to the path

insertion of the molar retainer. The gingival half of

d cormector. The occlusal half of the p ontic

attached to the m olar retainer and houses the female

th e nonrigid connector (Fig 7). This

Moulding et al^ have advocated the use of a

Fig 7 Segmented FPD with a split pontic containing a

nonrigid connector.

lternative procedure

A segmented FPD with a nonrigid connector between

the pontic and the molar retainer can be designed

without the disadvantages of the previously described

prostheses. The male portion of

tbe

nonrigid connec-

tor can be placed on the mesial surface of the molar

retainer and oriented parallel to the path of insertion of

the premolar retainer (Fig

),

The female section ofthe

International Volume 27 Number 8/1996

529

8/10/2019 Qi 27 8 Zuckerman 13

4/6

Fig 8 Segmented FPD with a nonrigid connector. The

premolar has the maie portion of the inleriock on its distal

surface. Note the iarge gingival embrasure between the

premolar and the pontic.

Size 1mm)

Smail

i_arge

A

70

ao

B

2.8

3.5

C

2.0

2.5

6.7

7.0

E

2.4

3.0

F

2 3

3 3

Fig 9 Segmented FPD with the maie portion of tiie

interiook on the mesial surface of the second molar retainer

The tooth preparation of the second molar is retentive hut

withoutr siioi pulpal exposure.

Fig 10

left)

Design and dimensions of PDC components.

Fig

below)

ivtale portion of the PDC on tfie mesiai axiai

wail of the moiar retainer. 1) Guiding piane; 2| crest of

ridge;

3] gingival end of male PDC contoured to ridge.

nonrigid connector is located under the pontic in the

anterior segment ofthe prosthesis.

This design is ideal for metal-ceramic restorations.

Both abutments are prepared for metal-ceramic com-

plete yeneer crowns with a path of insertion parallel to

their long axes. This allows the dentist to prepare the

teeth with maximum retention and minimal risk of

pulpa exposure.

The male and female components of this nonrigid

connecto r are manufactured in two sizes and are listed

in the catalogs of denial supply dealers as Plastic

Dovetail Connector (PDC} attachments (Fig 10). The

PDC attachments are designed so that the mating

surfaces of male and female components restrict the

movements of the two segments of the FPD to ore

plane. If the vertical height for the con nec tor is limited,

the PDC components may be reduced in height about

40% and still remain effective.

is dv nt ges

Use of

t is

design for FPDs with long spans should be

ayoided, particularly when the connector has beeti

530

Quintessence internationai Voiurne 27, Number 8/19 96

8/10/2019 Qi 27 8 Zuckerman 13

5/6

Zuckerman

g 12 Molar preparation with palh ot insertion along ts

Fig 13 Molar retainer with male porlion of the PDC on Ihe

mesial surface. The nonrJgid conneotor is aligned parallel to

Ihe path ol insertion of the premolar preparation.

g 14 Anterior section ot FPD placed over the PDC and

the premolar abutment.

Fig 15 Completed prosthesis atter insertior.

inheight. Slight movement of the abutmentto

the

pontics

are

rigidly connected

can

produce

the components ofthe

Another disadvantage of this design is that the

for asegmentedFPD arehigher than

of a rigidly assembled FPD. Furthermore,

are

unfamiliar with this

ofa nonrigid connectorandwill

to he instructed accordingly.

echnical procedure

Thediesandcastsarefabricatedandarticulatedas

for any FPD.

Waxpatternsaremadeforboth retainers.

The

male pattern

of

th e

PDC is

recessed into

the

mesial surfaceofth patternfor the molar retainer.

The male attachment is positioned parallelto the

path

of

insertion

of

the premolar retainer.

4. The guiding p lane of the connector is locatedin the

contact area between the molar retainer and the

pontic. The gingiva end of the connector is

conto ured to establish even contact with the crestof

the ridge Fig 11).

5.

The

female pattern

of

the

PDC is

piaced over

the

male pattern.Awax patternforthe ponticismade

over ihc female pattern. The gingival facing

end of

the assembled connector should present a smooth, un-

interrupted continuation of the ridgelapsurfaceof

the pon tic when the prosthesis has been com pleted.

6. The patterns of the pontic and the premolar

retainerareconnectedandcastas onepiece.

7.

The

sections

ofth

FPD framework

are

assembled

andthegingival embrasure betweenthemoiar and

ponticiscontoured with an abrasive separating disk.

Figures 12to 5illustrate the clinical applicationof

th e PDC,which is completely concealed withinthe

FPD,

International Volume27 Number 8 1996

531

8/10/2019 Qi 27 8 Zuckerman 13

6/6

Zuckerman

Summary

Segmented FPDs are a well-established methodre-

comm ended to overcotne the problems associated with

the insertion ofFPDswhen the abutments are severely

misaligned. Traditional designs used

to

create

seg-

mented FPDs were examined, and their disadvantages

were discussed.

A new design was suggested that does not have most

ofthe disadvantages associated with segmented pros-

theses . Manufactured plastic patterns that can be used

to create this segmented FPDdesign are available.

These economical, prefabricated, burnout patterns

simplify laboratory fabrication and produce uniform,

consistent,

and

reliable nonrigid connectors.

The

extracoronal application of an interiocking attachment

for segmented FPDs provides

a

practical solution

to a

difficult probiem.

References

1. Lubow

RM

Cootey

RL

Kaiser

D.

Periodontat

and

restorative

aspects

of

molar uprighting.

J

Prosthet Dent I982;47:37.1.

Shillingburg HT Hobo S. Whitsett LD. Fundamentals of Fixed

Prosthudonties,ed 2.Chicago: Quintessence, i9Bi.

1 Zuckerm an GR . Faetors that influence

the

meciianicai retention

the complete erown. Int JPros lhod ont 19SB;i; 36-20O.

4. Zuckerman GR. Resistance form for the complte veneer crown:

Principles ofdesign and anaiiis. Int JProsthodont t9S;l:302-: 07.

5. Rosenstiel SF. LandMEFujimotoJ Contemporary Fked Prostho-

dontics.

ed I. St

Louis: M osby.

19S8

6. O'Connor

RP.

Caughman

WF.

Bemis

C. Use of the

split pontic

nonrigid connector with

the

tilted molar abutment.

J

Prosthet Dent

1986;56:249-2;i.

7. Moulding MB, Holiand GA . Sulik WD.

An

alternative orientation

of

nondgid connectors

in

fixed partial dentures.

J

Prosthet Dent

8

532

Aesthetic Design

for Ceramic Restoratioi is

T

he most

natrural,

esthetic results

in dental

ceramics can

be achieved

with contem-

porary' techniques and this hook descrihes

how. Investigated are thecharacteristicsof

natural dentition, tissue tnanagement, impres-

sions, occlusal records, waxing techniques,

color,andlahorato r)' technique s, including

methodsfor anaesthetic ceramic m argin,

opalescence,anddevelopment ofth e dentine

mamelon. Filled with practical tips, this hook

is idealfordentistsandtechnicians.

59 pages; 292 color illus; ISBN -85097-034-3

ontents

1 StudiesofNatural Dentition

2 Dentist-Technician-Paticnt Communication

3 Tissue Management

for

Aesdietic

and Biological Ha rmo ny

4 Impressions artti Occlusai Records

5 Aesthetic Wax Diagnostic Control

6 Accurate Registration and Communication

of Colour Characteristics

7 Advanced Laboratory Techniques

8 Case Studies

quinlc/zcnca

book /

OrderNow

Toll free

1-800-621-0387

Fax 708 682-3288

Quitite.ssence Publishing Co,

Inc