Porcelain shoulder adaptation using direct refractory dies.
Eleven direct refractory dies were made from separate polysulfide rubber impressions of two Dentoform teeth which had been prepared for porcelain-fused-to-gold veneer crowns with labial porcelain shoulders. Porcelain veneer crowns were built and fired directly on the dies, following the manufacturer's instructions and using a common laboratory technique. The finished crowns were seated on the Dentoform teeth, and the porcelain-tooth adaptation was measured with a micrometer eyepiece in a dissecting microscope. In general, the study indicated that by use of a direct refractory die, the porcelain adaptation of an average porcelain shoulder veneer crown could be made to fall within the tolerances of a clinically acceptable gold margin (39 mu).21 The crown could likewise be made to adapt closer than the normal thickness of cement film may allow (20 to 40 mu).22 However the adaptation of many crowns was more uneven than the above statements would tend to indicate. The study also showed that with great care and a limited number of firings, margins of a lesser thickness than a piece of 0.001 inch (25.4 mu) platinum foil could be attained. There appears to be promise in the use of a direct refractory die material. However, more studies are needed to overcome some of the problems in the technique described.
D003442:Crowns; D003735:Dental Casting Technique / Q000295:instrumentation*; D003776:Dental Porcelain; D003779:Denture Design; D006047:Gold Alloys
D006047:Gold Alloys; D003776:Dental Porcelain