Effect of surface conditioning protocols on the repair bond strength of resin composite to CAD/CAM blocks: Bioactive-glass, silica-coated alumina, or aluminum oxide?

This study evaluated the repair bond strengths of ceramic and hybrid ceramic CAD/CAM restorations following bioactive-glass, silica-coated alumina, and aluminum oxide surface treatments. Shear bond strength (SBS) tests, surface roughness, and scanning electron microscopic (SEM) evaluations were performed on 180 specimens (7×12×2 mm³ and 5×5×3 mm³, respectively) of ceramic (IPS Empress) and hybrid ceramic (Cerasmart270) blocks. Samples were thermocycled (5°C-55°C, 5000 cycles) and silica-coated alumina, Al₂O₃, or bioactive-glass were used for surface conditioning. Resin composite was applied on substrate using two- (Tokuyama Universal) or one-bottle (G-Premio) universal adhesives, combined with the same brand universal shade composites (Omnichroma, Essentia Universal). SBS values were measured using a universal testing machine; failure types were analyzed using a stereomicroscope. Surface roughness was assessed with a profilometer, followed by SEM. Statistical analysis included ANOVA, Tukey HSD, and Fisher's Exact tests. The highest mean SBS values were observed for ceramics in conjunction with two-bottle universal adhesives. No statistically significant differences were found in the SBS values for different surface conditioning treatments except for hybrid ceramic conditioned with Al₂O₃. Bioactive-glass and silica-coated alumina caused similar surface roughness as indicated by the SEM images. A surface conditioning method and an adhesive system are both essential for hybrid ceramic repairs, while the adhesive system was more critical for ceramics.