Influence of surface treatment before glazing on wear and flexural strength of translucent zirconia

Objectives: To determine whether the surface treatment of translucent zirconia prior to glazing affects wear and flexural strength. Methods: Translucent zirconia disks were either left as-sintered, polished, or sandblasted. Half of the specimens within these three groups were glazed. Human enamel and dentin substrates were prepared as control. The wear volume and depth, as well as surface roughness parameters, were obtained after chewing simulation (n = 8 per group). Biaxial flexural strength of zirconia specimens was measured and fractures were analyzed. Statistics was performed with multifactorial ANOVAs (alpha = 0.05). Results: The overall wear volume was significantly higher on glazed surfaces (0.020 f 0.007 mm(3)) compared to non-glazed zirconia (0.001 f 0.001 mm(3); p < 0.001). No significant difference in wear volume was found among different surface treatments (p = 0.368). Nevertheless, wear volume significantly increased when rough antagonists were used for zirconia and tooth substrates (both p < 0.001). The lowest wear volume was measured on polished zirconia (< 0.001 f < 0.001 mm(3)) and highest on dentin (2.327 f 1.686 mm(3)). The flexural strength was significantly higher for polished zirconia surfaces (652 f 135 MPa) than for all other groups (p < 0.001). Significance: Lowest wear and highest flexural strength of a translucent zirconia restoration can be expected when the surface is polished. When applying glaze, the prior surface treatment does not affect wear. Applied to clinical situations, perfect surface polishing after occlusion adjustments is recommended to prevent increased wear of the antagonist.