An indirect-direct method of crown fabrication for existing removable partial denture clasps

DENTAL DANIEL

TECHNOLOGY

H. GEHL.

Section editor

An indirect-direct existing Gerald Don& Medical

method

removable

n for

of crown

partial

denture

clasps

H. loft, D.D.S.,* J. Marvin Reynolds, D.D.S.,** and 0. Lundquist, D.D.S.*** College of Georgia, School of Dentistry, Augusta, Ga.

A

butment teeth for removable partial dentures may become carious in patients who do not practice good plaque control. If the partial denture is otherwise satisfactory, some form of crown may be needed to restore the abutment tooth. The fabrication of crowns in conjunction with removable partial dentures is beset with several problems. Obtaining an accurate impression of the preparation, maintaining the correct relationship of the removable partial denture to the preparation when the indirect method is used, and finalizing the wax pattern directly in the mouth present the most critical problems. In addition the final fit of the crown to the partial denture clasp, regardless of the technique that is used, is affected in two ways. One is by the expansion of the investment and the shrinkage of the gold which create a slightly different outer contour than had existed in the pattern. This change is minor; the major error arises because a finished crown does not fit the preparation as exactly as the pattern fits the die or tooth. The following indirect technique finalizes the wax pattern on a cast coping that becomes a part of the final crown. The final crown will fit the abutment as exactly as does the coping. The only error possible is in the external form and cementation. TECHNJQUE

( 1) Prepare the abutment tooth to receive the type of crown that is indicated. Make sure that there is at least 1 mm. of clearance between the preparation and all elements of the removable partial denture clasp. *Associate **Professor, ***Professor

Professor,

Department

Department

of Restorative

of Restorative

and Coordinator,

Dentistry.

Dentistry.

for Occlusion.

589

590

Loft,

Reynolds,

Fig. 1. The cast coping will be cast to it.

J. Prosthet. Dent. November. 1977

and Lundquist

with

mechanical

retention

established

Fig. 2. The cast coping on the tooth with the removable Fig.

3. Duralay

has been painted

under

partial

for the external denture

contours

and the occlusal

surface

that

in place in the mouth.

the clasp arms and the occlusal

Fig. 4. The removable partial denture has been removed and the remaining of the crown and occlusal surface are ready to be developed in wax. Fig. 5. The external

contours

have been finalized

rest.

external

contours

in wax and are

ready to be cast.

(2) Make an impression of the preparation using an acceptable technique and material. (3) Make a die for fabrication of the pattern. (4) Make a wax coping over the die that does not exceed 0.5 mm. in thickness. (5) Finalize the gingival margins and the lower 1 mm. of the outer contour. (6) Establish some mechanical retention in the outer aspect of the remainder of the coping pattern. ( 7) Cast the wax coping (Fig. 1) . (8) Try the coping on the preparation and finish the margins. (9) Seat the removable partial denture in the mouth (Fig. 2).

Volume 38 Number 5

Indirect-direct

crown fabrication

591

(IO) Make sure that the clasp does not contact any part of the coping. Paint Duralay* on the coping under the element of the clasp and rest, while maintaining an accurate relation of the removable partial denture to the teeth (Fig. 3). ( 12) Remove the partial denture (Fig. 4) . (13) Add wax to the remainder of the coping to complete the contour and the occlusal form (Fig. 5). (14) Cast the outer contours, which have been formed in Duralay and wax, to the coping. ( 15) Solder the margins of the casting to the coping. (16) Finish and cement the crown on the prepared tooth. (11)

SUMMARY

A technique that uses a combined indirect-direct method for the fabrication of a crown under an existing removable partial denture clasp has been presented. Advantages of this method are as follows: ( 1) The coping is placed directly on the preparation so the rest and retentive surfaces are more accurately developed than with other methods. (2) Fewer adjustments are required because of the accuracy of this method as compared with waxing the crown in one step. *Reliance

Dental

Mfg. Co., Worth,

111.

MEDICAL COLLEGE OF GEORGIA SCHOOL OF DENTISTRY AUGUSTA, GA. 30902

1

I

1 ARTICLES Using

TO APPEAR

pantographic

tracings

James M. Shields, D.D.S., decker, D.D.S., M.S.

Occlusatty

oriented

Barry Shipman,

Rational

IN FUTURE

MS.,

to detect

for

and John McCasland,

use of endosteal

TMJ and

Joseph A. Clayton,

impressions

D.M.D.,

ISSUES

targe

muscle

dysfunction

D.D.S.,

M.S., and Larry

maxillary

stomas

D.D.S.

implants

Carl H. Smith, D.D.S.

Extmeoronal Oskar Sykora,

removable M.A.,

D.D.S.,

partial Ph.D.

denture

service

in Canuda

D. Sindle-