Influence of Zirconia Type and Surface Treatment on the Shear Bond Strength Between Veneering Porcelain and Zirconia

Background: Proximal contact loss is a major problem in zirconia restorations on implant abutments. This study investigated the effect of surface treatments on the shear bond strength (SBS) between veneering porcelain and translucent zirconia (4Y-PSZ and 5Y-PSZ) compared with conventional zirconia (3Y-TZP). Methods: Forty-four specimens of each zirconia type (10.0 × 7.0 × 1.0 mm) were prepared and randomly assigned to four surface treatment groups: control (C), grinding with 150-grit silicon carbide paper (GR), airborne-particle abrasion with alumina particles (AB), and glazing (GL). Surface roughness (Ra) was measured for one specimen from each treatment group. Veneering porcelain cylinders (2.38 mm in diameter, 0.5 mm in thickness) were fabricated and bonded to the zirconia surfaces. SBS was evaluated using a universal testing machine (n = 10). Data were analyzed using two-way ANOVA and Tukey’s HSD test (α = 0.05). Results: The GL group exhibited the lowest Ra, whereas the AB group showed the highest Ra. Regarding zirconia type, 3Y-TZP demonstrated significantly higher SBS than 5Y-PSZ, while no significant differences were found between 3Y-TZP and 4Y-PSZ or between 4Y-PSZ and 5Y-PSZ. The AB and GL groups showed significantly higher SBS than the C group, whereas the GR group did not differ significantly from the C group. Conclusions: Airborne-particle abrasion and glazing effectively enhanced SBS across the zirconia types evaluated prior to veneering.