Shear bond strength of feldspathic porcelain in metal ceramic crowns and failure mode after multiple firing cycles (In-vitro Study)

Abstract

Purpose: To investigate the effect of multiple firing cycles on shear bond strength and failure mode of porcelain fused to metal. Materials and Methods: thirty porcelain fused to metal discs were divided into three groups according to number of firing cycles subjected to; group A; three firing cycles, group B; five firing cycles and group C; seven firing cycles to sinter the porcelain. All the specimens were labeled and stored in distilled water for 48 hours before testing. Shearing test was done by compressive load applied using a chisel shaped metallic rod attached to the upper movable compartment of testing machine traveling at cross-head speed of 1 mm/ min. Fractured specimens were ultrasonically cleaned, carefully checked. All failures mode were analyzed. Results: The test results showed a statistically significant difference in the mean shear stress averages among the three studied groups (p