Compatibility of Ceramic-Ceramic Systems for Fixed Prosthodont ics

This study evaluated dilatometric data for predicting ceramic-ceramic compatibility for porcelains fied on central incisor copings (n = 72) of high expansion colored IPS-Empress porcelain. Nine body porcelains (leucite 0 wt% to 51 wt%) were each fired onto eight copings. Cracks were detected at 10 x magnification using transilluminating light. Failure was defined as the rpesence of at least one crack and probability of failure (Pf) as the ratio of failed to total crowns. Thermal contraction coefficients (a) were determined using four bars of each porcelain followin g the protocol of ISO 9693. Absolute differences in thermal contraction, [ a], between core and test porcelains were plotted against Pf and curve fit. Significant differences in a were found among the porcelains tested (ANOVA, 95% Tukey); the a values ranged from 7.92 to 17.83 x 10 to the negative sixth power/degrees C; Pf ranged from 0 to 1. Compatible porcelains (no cracks during any firing of all eight crowns) had [ a] values less than 1 x 10 to the negative sixth power/degrees C. Absolute values ([ a]) were surprisingly predtive of Pf given the very different cooling rates (dilatometry versus dental lab) and the relatively complex crown shape. Standard dialtometry may be useful for predicting the compatibility of ceramic-ceramic systems. Three porcelains, IPS-Empress dentin, Duceram, and Will-Ceram were successfully used for veneering IPS Empress cores.