Influence of inner crown thickness on the bonding strength of porcelain fused to Co-Cr alloy endocrown.

PURPOSE: The purpose of this study was to investigate the influence of inner crown thickness on the bonding strength of porcelain fused to Co-Cr alloy endocrown by shear strength test. METHODS: According to the molar average anatomical data to obtain a simplified model for endocrowns, porcelain fused to Co-Cr alloy endocrowns were fabricated with four inner crown thicknesses: 0.3 mm, 0.5 mm, 0.8 mm, and 1.0 mm group, eight specimens were fabricated for each thickness group. Shear bond strength test was used to observe the metal-porcelain bonding strength, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analysis were performed after the test to evaluate the interface of metal-porcelain. RESULTS: The shear bond strength means (in MPa) were: 10.50 +/- 2.55 (0.3 mm), 13.21 +/- 2.27 (0.5 mm), 14.47 +/- 1.46 (0.8 mm), and 15.78 +/- 2.81 (1.0 mm), one-way ANOVA showed that there was a statistically significant difference among the thicknesses (P < 0.05). The SEM observation showed tight bonding, and the EDS analysis showed element diffusion phenomenon at the metal-porcelain interface. CONCLUSION: The bonding strength of porcelain fused to Co-Cr alloy endocrown varied according to the different thickness of inner crown and the thinner inner crown was recommended for tooth defects with limited prosthodontic space.