The porcelain-fused-to-metal telescope:
A simple apprach to salvaging existing crowns with recurrent decay
By Paul J. Berson, DDS
As the median life expectancy in the United States keeps increasing, the restorations being placed by today's dentists are being tested over a longer period of time. It is not always feasible to remake an entire prosthesis when a maintenance problem arises?the patient's health may preclude the many necessary visits for a total remake, or the patient's financial situation may prevent constructing a new prosthesis.
Fortunately, with the success of implants and advanced periodontal procedures, it is possible to provide fixed restorations that will last most patients their entire lives. These same techniques can be used to retrofit and save already-existing cases, which will allow patients to maintain the same quality of life they have been experiencing with their own dentition at a minimal cost.
The telescopic restoration is a technique that can solve the problem of recurrent decay under an existing restoration.1 A telescope usually is an all-gold coping that is cemented on top of a full-coverage crown preparation.2 The final fixed restoration is fitted and cemented on top of the telescope. The telescope margin defines the apical extent of the prepared tooth structure as well as the gingival contour of the final restoration.
Often, the gingival collar of the telescope extends occlusally to the free gingival margin. Consequently, the overcase abuts the telescope supragingivally (Fig. 1). Since the telescope may extend supragingivally, it may not be possible to make the telescope entirely out of gold and fulfill the patient's esthetic needs. The following case report describes a porcelain-to-gold telescope retrofitted to an existing reconstruction with recurrent decay under one of its abutments.
The patient, a 48-year-old man, had a fixed reconstruction from teeth No. 15. Teeth No. 5-11, 13, and 15 are abutments. Teeth No. 5 and 15 had preexisting telescopes. The only problem of recurrent decay was in tooth No. 6. This decay had destroyed the clinical crown of the tooth (Fig. 2).
The fixed restoration was removed during the initial visit. The decay was removed from tooth No. 6, endodontic therapy was completed (Fig. 3), and a post preparation was made (Fig. 4). The old crown of tooth No. 6 was relined with acrylic and carved to fit the remaining tooth structure (Fig. 5).
A wax post was placed and an impression of the post and tooth preparation was taken (Fig. 6). A thin duralay coping was made on the die /Fig. 7). This coping was placed on the tooth and the fixed restoration was seated on top of it. Sometimes, the overcase needs to be trimmed back to create enough room for the duralay coping.
After it was determined that there was enough room under the overcase for a casting, the inside of the abutment was coated with vaseline and relined. Duralay was added to the inside of the abutment and the entire prosthesis was reseated. The patient was directed to stay in full intercuspation. After the duralay set, the fixed restoration was removed and the duralay coping was carved to fit the gingival contour and the overcase (Fig. 8 and 9). A shade was selected for the porcelain gingival collar.
An impression was taken of the duralay coping (Fig. 10). This was to serve as a matrix for the porcelain gingival collar contour. The duralay coping was re?seated on the die and its margins were waxed. The labial gingival collar of the duralay coping was cut back and the duralay coping and post were casted. The porcelain was added back to the previously established contours as checked against the matrix impression (Fig. 11).
The final telescope was seated (Fig. 12) and the overcase was seated over the telescope. A final radiograph was taken to determine whether the restoration was seated completely (Fig. 13). The telescope was cemented with a more retentive cement than was used for the overcase (Fig. 14).
Being able to maintain restorations over long periods of time can be more of an art than a science. As patients live longer, dentists constantly need to be creating new solutions to maintenance problems. The telescopic retainer is a technique that can be useful for all restorative dentists.
Dr. Berson is an assistant clinical professor of restorative dentistry at the University of Pennsylvania School of Dental Medicine in Philadelphia.
1. Amsterdam M. Periodontal prosthesis-Twenty-five years in retrospect. Alpha Omegan 1974;Dec.:14-15.
2. Casullo, Matarazzo. The use of telescopes in general dentistry. Alpha Omegan 1977;Dec.:20-22