Influence of Tooth Surface Pretreatment Procedure on Bond Strength of Self-Adhesive Cement—An In Vitro Study

Objectives: Reliable bonding is essential for the longevity of zirconia restorations. This in vitro study evaluated whether tooth surface pretreatment with a cleaning agent influences the bond strength of zirconia overlays cemented with a self-adhesive resin cement under simulated aging conditions. Methods: Twenty-three intact third molars were collected. Three specimens were used for surface roughness measurements. Twenty specimens were prepared by exposing dentin surfaces and creating standardized retentive cavities. Micro-CT was performed to calculate precise dentin and enamel area proportions. Zirconia overlays were fabricated and cemented using a self-adhesive resin cement. Specimens were randomly assigned to one of two groups: a control group (n = 10) or a test group (n = 10), where a cleaning agent (Katana Cleaner) pretreatment was applied. After cementation, all specimens underwent 5000 thermocycles. Tensile bond strength was assessed, and failure modes were classified as adhesive or cohesive. Results: Linear regression analysis showed that dentin and enamel surface areas were the main factors associated with failure force, although the overall model fit was modest (adjusted R2 = 0.17, p = 0.1169). No statistically significant difference in failure rates was found between the pretreated group and control group (Fisher’s Exact test, p = 0.3034). No significant differences in failure modes were identified between the two groups. Roughness results show that etching with acid reduced the actual surface area by 1 to 1.5%, while further cleaning with Katana Cleaner led to further reduction by 0.1%. Conclusions: Bond strength of zirconia overlays cemented with self-adhesive resin cement appeared to depend primarily on substrate area and cavity retention. Additional tooth surface pretreatment with a cleaning agent did not significantly improve bond strength under the tested conditions.