Design of a direct retainer for removable partial dentures

Design partial

of a direct dentures

retainer

for

Majid N. Rad, D.D.S.,* and Mohamad National University of Iran, Evin, Tehran,

removable

A. Yarmand, Iran

D.D.S.,

M.S.**

I

n many instances, teeth to be utilized as abutments for direct retainers have an insufficient amount of desirable undercut to hold the ordinary retainer. This technique describes the kind of direct retainer that can be used under these circumstances. PROCEDURES 1. Select the proper tray, and make an alginate (irreversible hydrocolloid) impression of the arch on which the removable partial denture is to be made. 2. Make an alginate impression of the opposing arch. 3. Pour stone casts in the impressions. 4. Make the necessary interocclusal records. 5. Mount the casts in an instrument for initial evaluation of the occlusion. 6. Make the initial survey of the cast (Fig. 1) .

Fig.

1. The

initial

survey

Fig. 2. The blocking direct retainer.

*Assistant **Associate

out

of the diagnostic of the undesired

Professor, Department Dean and Associate

cast. undercuts

of Prosthetics. Professor, Department

and

preparation

of the shoulder

for

the

of Prosthetics. 457

Figs.

Fig.

5. The

waxed

retainers

Fig.

6. The

sprued

wax-up

Figs.

7 to 9. The

compl&ted

3 and 4. The

showing ready

completed

contact

wax-up

of only

of the framework.

the crowns

of the teeth.

for investing.

removable

partial

denture

casting.

7. Block out the undesirable undercuts, and prepare the shoulder retainer to be used (Fig. 2) 8. Make an impression of the cast, and pour a refractory cast. 9. Outline the restoration on the refractory cast. 10. Complete the wax up. Note that the waxed retainer contacts crowns of the teeth (Figs. 3 to 5).

for

the

only

the

Direct 11. 12. 13. 14.

retainer

for

partial

dentures

Sprue, invest, burn out, and cast the retainer in the usual manner Remove the sprues, and finish the casting. Try the finished framework in the mouth (Figs. 7 to 9). Complete the removable partial denture in the usual manner.

459

(Fig. 6).

SUMMARY The direct retainer described in this technique is utilized on abutment with a minimum of desirable undercut. Only the arms of the retainer contact the tooth. All other parts are relieved. NATIONAL UNIVERSITY SCHOOL OF DENTISTRY EVIN, TEHRAN, IRAN

OF IRAN

teeth should