ABSTRACT
This study was performed to find an acceptable internal adaptation of castable ceramics containing mica and beta-spodumene crystals. The influences of factors, expansion rate of phosphate-bonded investment (A), anisotropic expansion (B), diecoating (C), shrinkage during crystallization (D), and interaction (A x B), and (A x C) were tested by twice repeated experiments under block design according to L8(2)(7) orthogonal array. Estimated mean ranges under the conditions combined with significant factors were judged by considering the criteria of the ideal internal gap (about 50 microm). The ideal marginal fit of less than 50 microm and uniform cement space about 50 microm around the axial wall could be achieved by a combination of optimum levels of A1B1C2D2. However, the estimated mean gap at the cusp tip and central fossa of occlusal inside by this combination were about 120 microm. The near intolerable gaps could not be reduced.
Subject(s)
Crowns , Dental Marginal Adaptation , Dental Porcelain , Dental Prosthesis Design , Aluminum Silicates , Analysis of Variance , Dental Casting Investment , Dental Casting Technique/instrumentation , Dental Porcelain/chemistry , Dental Prosthesis Design/methods , Humans , Linear Models , Minerals , Models, DentalABSTRACT
PURPOSE: The study compared the probability of failure of three highly filled resin-veneered restorations to that of conventional metal-ceramic restorations when used as implant-supported prostheses. The effect of the location of load application on the fracture resistance of the restorations was also studied. MATERIALS AND METHODS: Twenty samples each of the three resins, Artglass, Targis, and Estenia, were applied on type IV gold frameworks. Twenty metal-ceramic restorations of equal dimensions (VMK 95 and Degudent Universal) were used as controls. Compressive load was applied vertically at 1 mm (n = 10) and 2 mm (n = 10) from the periphery of the occlusal table until the restorations failed. Weibull analysis was applied to the data. RESULTS: There was no significant difference in the probability of failure among the metal-ceramic restorations and three resin-veneered restoration systems. Loading the resin-veneered restorations at the 1-mm location significantly increased their probability of failure when compared to the 2-mm loading location. The loading location did not significantly change the probability of failure of the metal-ceramic restorations. CONCLUSION: The probability of failure of resin-veneered restorations tested was not significantly different from that of the metal-ceramic restoration under two compressive loading conditions. Eccentric loading of resin-veneered restorations should be minimized in light of the higher probability of failure associated with such a loading condition.
