Comparative study of fracture resistance of ceramic in metal ceramic restorations by using three different metal coping designs fabricated by direct metal laser sintering technology: An in vitro study.

Aim: The aim of this study was to compare the effect of different metal coping designs on fracture resistance of porcelain in metal ceramic restorations fabricated by direct metal laser sintering technology. Settings and Design: Comparative - In vitro study. Methods and Material: An ivorine central incisor tooth was selected and prepared according to biomechanical principles followed by fabrication of nickel-chromium dies according to conventional casting method. The direct metal laser sintered copings on the dies were made and divided in three groups consisting of metal coping extending up to gingivo-axial line angle of finish line, metal coping extending 1mm short of gingivo-axial line angle of finish line, metal coping having 0.4mm wide labial metal collar respectively. Ceramic layering of the metal copings was done and fracture resistance of the specimens were measured. Statistical analysis used: Data for the fracture load for all the groups were evaluated and compared and was tested for normality using Shapiro-Wilk test. The 3 groups were compared using the Kruskal-Wallis test (Non-parametric ANOVA). Results: The mean fracture resistance of Groups A, B, C was 971.8N, 705.2N, 531.66N respectively. Conclusions: The mean fracture resistance of the specimens with shoulder porcelain labial margins having metal coping design extending up to gingivo-axial line angle of the finish line was highest as compared to other groups.