Effect of chemical pretreatment on shear bond strength of universal adhesive in the repair of CAD/CAM hybrid ceramics

Purpose: This study aimed to evaluate the effect of additional chemical pretreatment using silane and MDP prior to the application of universal adhesive on the shear bond strength during the repair of CAD/CAM hybrid ceramics.Two types of hybrid ceramics with different characteristics were used to compare shear bond strength.Materials and Methods: Two hybrid ceramics (Vita Enamic and Celtra Duo) were used in this study.To simulate intraoral aging, all specimens underwent 10,000 cycles of thermocycling in water.After surface polishing and etching with 4% hydrofluoric acid, the specimens were divided into three groups according to the pretreatment method: Group 1 (no pretreatment), Group 2 (silane application), and Group 3 (silane + MDP application).Scotchbond Universal Plus was applied to all specimens, followed by bonding of composite resin using a cylindrical mold (2.4 mm in diameter, 2 mm in height).The specimens were stored in 100% relative humidity at 37°C for 24 hours, and then shear bond strength was measured.Two-way ANOVA was conducted to analyze the effects of ceramic type and pretreatment method, followed by one-way ANOVA and Scheffe post hoc tests when significant differences were found.A significance level of 0.05 was used for all statistical analyses.Results: Both Vita Enamic and Celtra Duo exhibited the lowest shear bond strength when only universal adhesive was applied.In Vita Enamic, all pretreatment groups showed increased bond strength, but no significant difference was observed between pretreatment methods.In Celtra Duo, the group treated with both silane and MDP showed the highest bond strength (P < 0.05).Conclusion: Even when using a universal adhesive containing silane and MDP, the effect of pretreatment varies depending on the type of hybrid ceramic.Therefore, selecting an appropriate chemical pretreatment method based on the characteristics of each material is essential for successful repair.(