Bond strength of Y-TZP-zirconia ceramics subjected to various surface roughening methods and layering porcelain

The interface between yttrium oxide partially stabilized tetragonal zirconia polycrystalline (Y-TZP) core and veneering porcelain is the site of most clinical failures. Many efforts have focused on increasing the bond strength between Y-TZP core and veneering porcelain, and such approaches include increasing the surface roughness and providing undercuts. However, each surface roughening method carries limitations. The specific aim of this study was to test the bond strengths of Y-TZP subjected to different methods (sandblasting, fine polising, and rough polising) and of veneering porcelain. Presintered zirconia blocks with rectangular parallelepiped shape were prepared, and the surfaces were roughened with different methods before sintering. Shear strength of each zirconia-veneer interface was measured from 15 specimens. The surface at the fractured areas after shear test was investigated using an optical microscope. In conclusion, Y-TZP subjected to sandblasting showed inferior shear strength compared to other groups. Cohesive fracture was observed in the sandblasting group; combination of cohesive and adhesive fracture was observed in the control, fine polishing, and rough polishing groups.