Correlation between Surface Roughness and Shear Bond Strength in Zirconia Veneering Ceramics: a Preliminary Report

Delamination and chipping of veneering porcelain were described as the most frequent reasons for the failure of zirconia fixed partial dentures. Aim: The aim of the study was to assess the correlation of surface roughness and the shear bond strength of veneering ceramics to zirconia core. Materials and methods: A total number of 10 zirconia samples, 5 in each group were sintered. Samples in the first group were ground, and in the second were ground and sandblasted. After the surface treatment, veneering ceramic was fired to the core up to the thickness of 3 mm, the samples were embedded in the PTFE molds using PMMA resin and subjected to shear force until fracture occurred. The surface roughness was assessed prior to application of veneering ceramics by the Stylus instrument Perthometer S8P and Ra (mean roughness) and Z values (distance from the highest to the lowest point of measurement along the observed line) were obtained. Results: Ground and sandblasted samples had significantly rougher surface (p<0.01) and showed significantly higher shear bond strength (p<0.01). Conclusion: The positive and significant correlation was found between surface roughness values and shear bond strength. Further research is needed to completely elucidate the observed relation.