Apparent fracture toughness of metal ceramic restorations with different manipulative variables

Abstract

Apparent fracture toughness (K c) is a measure of the strain absorption capacity of brittle materials. It relates to the level of tensile stress that must be exceeded at the tip of a crack before failure occurs. Using an indentation technique, this study measured K c and elastic modulus-to-hardness ratio ( E H ) of 65 metal ceramic crowns made with 13 different variables. The variables studied were (1) brand of porcelain, (2) firing temperature, (3) condensation, and (4) modeling liquid. Statistically significant differences in K c and E H were found in respect to porcelain brand and between two of the modeling liquids. No significant differences were found in respect to altering firing temperature or condensation.