Influence of surface roughness on crack formation in a glass-ceramic bonded to a resin composite base.

The objective of the present study was to assess the influence of the roughness of a loaded surface on crack formation in a mica-based glass-ceramic bonded to a resin composite base. Five different surface roughnesses were created on glass-ceramic discs by serial wet-grinding with silicone carbide abrasives. The thicknesses of the ceramic discs were 1.50 +/- 0.01 mm. Resin composite discs were bonded to the ceramic surfaces opposite to the ground surfaces using an adhesive resin composite cement and a silane coupling agent. A compressive load was then applied at the center of the ground ceramic surface. The loads at initial radial and cone crack formations in the ceramic were measured macroscopically. In three of the five groups, the initial radial crack formations could not be observed due to the high roughness of these surfaces. Statistical analysis was performed using Student's t test for initial radial cracks and one-way ANOVA for the cone cracks. There were no significant differences between the two groups for the initial radial cracks or among the five groups for the cone cracks (P < 0.05). The roughness of the loaded surface had no influence on crack formation in the bonded mica-based glass-ceramic.