DANIEL H. GEHL
Restoration of removable partial denture rest seats using dental amalgam John T. Stamps, D.D.S.,* and Robert A. Tanquist, Fort Washington,
Md., and APO New York
any acceptable techniques have been advanced for the repair of fractured defective restorations or caries under the rests of removable partial dentures. Most rest seats, however, require gold as the restorative material of choice, but time, economics, and health of the periodontium may become a major consideration. Sound enamel or a carefully contoured cast restoration is the surface of choice beneath the clasp and rest of a removable partial denture. However, from an economic and realistic point of view this is not always possible, and a practical alternative is needed in certain situations. The following considerations should be given in the evaluation of which technique to use. 1. Is the removable partial denture stable without the rest functioning? If not, can it be made stable by restoration of the rest seat? 2. Is the removable partial denture still serving its original function, or will it, if the rest is restored? Could it be made more servicable if relined or modified? Partial dentures, like all dental restorations, are subject to wear and damage and should be evaluated periodically to ascertain the need for replacement, modification, or restoration of occlusal function. 3. Is the rest seat on a periodontally involved tooth? If so, the added expense of using a cast restoration may be contraindicated, and a less expensive restoration will still support the partial denture framework. 4. Are the tooth cusps basically sound and in *Lieutenant Colonel, USAF; presently Officer in Charge, USAF Dental Clinic 1, Andrew Air Force Base, Md., formerly Chief, Department of Restorative Dentistry. RAF Lakenheath, England. **Colonel, CSAF; Chief, Depaitment of Prosthetic Dentistry, RAF. Mildenhall, England.
Fig. 1. Adequate plished.
occlusal function? If so, then an amalgam restoration is more conservative of tooth structure than a more extensive and complex onlay or crown restoration. If occlusal contact is destroyed through fracture or caries, then cast gold is the restoration of choice. 5. Does the retentive clasp tip still rest on enamel or must it be placed on the restoration? If the retentive tip still rests on enamel, then an amalgam restoration is ideal. If not, then some type of casting is the restoration of choice. The reciprocating clasp may rest on either enamel, amalgam, or gold. 6. Does the dentist have the required time and skill to refit the framework to a new cast restoration or fabricate a cast restoration to fit the framework? If, after evaluation, the decision is made to use amalgam, the following steps are suggested: 1. Remove all dental caries after the placement of a rubber dam. 2. Establish the retention and convenience form for the restoration. 3. Seat the removable partial denture to insure clearance for amalgam pluggers (Fig. 1). Access is necessary to permit the plugger to reach all parts of the preparation beneath the rest. If access is not
REST SEAT RESTORATION
Fig. 2. Inadequate plugger access for amalgam condensation. Fig. 3. A “window” has been prepared to allow plugger access
Fig. 4. A, Pins have been shortened to allow plugger access when replacing cusp. B, 7‘1~ pin. do not interfere with placement of the removable partial denture. established at this time (Fig. 2), incomplete condensation of the amalgam may result, with a cotisequent compromise of the rest seat. 4. Prepare a “window” (Fig. 3) to gain access to beneath the rest. 5. Remove sharp angles of the preparation not directly accessible to the amalgam pluggers. 6. Place pins as required, using a rubber dam technique to preclude aspiration or swallowing of pins and to assure a dry operating field. Pin placement must not interfere with access for amalgam pluggers or seating of the removable partial denture. If necessary, shorten the pins where this may occur (Fig. 4). 7. Paint the teeth and the preparation with copalite and remove the rubber dam. 8. Select a matrix. For large restorations, a copper band that surrounds the entire tooth may be necessary. If so, festoon the gingival surface of the band to conform to gingival tissues and minimize damage. Remove parts of the copper band that would prevent correct placement of the removable partial denture (Fig. 5). Crimp the band as necessary. If the restoration is not extensive, use standard 0.002- or O.OOl.iinch matrix material (Figs. 6 and 7).
Fig. 5. The copper matrix band. Note that the band has been trimmed to allow the partial denture to seat. 9. Seat the removable partial denture over the band or matrix material to insure insertion without interference. 10. Polish the underside of the rest to a smooth surface for condensation of the amalgam against it. The buccal-lingual width of the rest can sometimes be reduced without loss of strength (Fig. 8). This will allow more plugger access without sacrificing sound tooth structure. 11. Reinsert the removable partial denture over the matrix.
Fig. 6. A, Standard Universal 0.002-inch band material with the ends cut off to serve as a matrix retainer. B, Preburnish the band to allow the amalgam to be packed against the framework.
Fig. 7. An explorer is used to remove amalgam so that it will not interfere when removing the partial denture. Fig. 8. The mesiobuccal width of the rest has been reduced. Fig. 9. The restoration has been stabilized with modeling compound. The teeth are dried and coated with cqpalite prior to placing the modeling compound to insure adhesion of the modeling compound to the tooth and the framework.
Fig. 10. The appearance of fresh amalgam following removal of the removable denture. Fig. 11. Note that the rest seats or guide planes are not polished. Fig. 12. The finished restoration. 12. Stabilize the restoration on all teeth which it contacts with modeling compound. Heat the compound over a flame or in hot water until soft. Then flash it over a flame to make the outer surface sticky. Dry the teeth and apply copalite so that the modeling compound will stick to the tooth and framework (Fig. 9). 13. Insert a wedge when needed. If the guide
planes are relatively straight, wedging is not required, since the restoration will hold the band against rhe tooth. If there is tipping of the teeth, then a wedge should be inserted between the partial denture and the band to preclude packing amalgam into the periodontal space. 14. Burnish the band material against the framework to reestablish the original guide planes.
FEBRUARY1979 VOLUML 41
REST SEAT RESTORATIOK
15. Condense the amalgam. Spherical amalgam is preferable because it flows easily in the plastic state into tight spaces and around pins. 16. Allow approximately 5 minutes for spherical amalgam to gain initial set prior to carving. Use an explorer around the periphery of the rests and clasps to insure no amalgam interference when removing the removable partial denture (Fig. 7). Be certain that the fresh amalgam has sufficient strength prior to the removal of the partial denture and matrix. 17. Finish the carving (Fig. 10). Do not overcarve guide planes established in the burnishing procedure. Carefully remove and reinsert the removable partial denture for rest adaptation. 18. Instruct the patient not to remove the removable partial denture for 24 hours. Polish the restoration 24 hours later. Do not polish rest seats or guide
planes (Figs. 10 to 12). Carefully reevaluate the fit of clasp arms and the rest seat of the removable partial denture on the tooth and in all other relationships of fit and function and make the necessart: adjustments and refinements. SUMMARY This anatomically contoured, carefully restored tooth is now capable of continuing to serve as an abutment for the patient’s existing removable partial denture, and a complex and extensive treatment has been avoided. Hepmlrequests to. DK. JOIIY T. S?.AHS ST. 125 11 PARKTOE FT. WASHINGIW, MI,. 20022
ARTICLES TO APPEAR IN FUTURE ISSUES C&on+made
perforated cyst decompression stents
Stephen M. Parel, D.D.S.
A combination obturator Gregory R. Parr, D.D.S.
Modification of stone dies for fabrication of porcelain jacket crowns Ronald G. Presswood,D.D.S., David Choate, and John Choate
A comparison of the casting accuracy of base metal and gold alloys Frank E. Pulskamp, D.D.S.
Utilization of cadaver tissue for a scanning electron microscopic study of the insertion of the masseter muscle Robert W. Rudd, D.D.S., Hey1 G. Tebo, M.A., D.D.S., and Gerald .J. Pinero, Ph.D.
Computer-monitored radionuclide tracking of three-dinwnsional mandibular movements. Part I. Jean A. Salomon, Ph.D., and Bernard D. Waysenson, D.C.D., D.S.O.
-IWE JOURNAL OF PROSIHETIC DENTISTRY