[Accuracy of fit of veneer crowns with ceramic shoulders]

Two different types of special ceramic shoulder powders were used for veneering 40 casted crowns. A total of 2400 measurements of the marginal defects provide information on the marginal qualities of the facially butted porcelain margins. Surfaces and shapes of the margins were compared by SEM and metallographic sections. Vita shoulder porcelain, with glazed surfaces and rounded edges of the facial margins, shows poor marginal adaptation. The veneers made of Ducera shoulder porcelain exhibit minor facial openings and high form stability during sintering. The higher content of aluminum oxide in this porcelain powder reduces sintering shrinkage but, at the same time, produces a rough surface. The use of a new experimental liquid failed to improve the results.