Effect of Etching Protocols on the Bonding Performance of a HEMA-Free Two-Step Universal Adhesive to Caries-Affected Dentin.

PURPOSE: To assess the bonding performance of a two-step universal adhesive applied in etch-and-rinse and self-etch protocols to caries-affected dentin. METHODS AND MATERIALS: Mid-coronal dentin surfaces were obtained from extracted human molars and assigned to either sound or caries-affected dentin groups. Specimens were randomly distributed into 12 subgroups (n = 10) based on adhesive type (G2-Bond Universal, Gluma Bond Universal, Clearfil S3 Bond Universal), bonding protocol (self-etch or etch-and-rinse), and evaluation period (24 h or aging). Resin composite blocks were fabricated and subjected to shear bond strength testing after 24 h or 10,000 thermocycles. Fourier-transform infrared spectroscopy was employed to measure the degree of conversion of each adhesive. Statistical analyses included ANOVA, Weibull analysis, and Kruskal-Wallis tests (α = 0.05). RESULTS: Adhesive type and bonding protocol significantly influenced bond strength (p 0.001), whereas substrate condition and thermocycling had no significant impact (p > 0.05). After aging, Clearfil S3 Bond Universal in the self-etch protocol presented considerably lower bond strength to caries-affected dentin compared with G2-Bond Universal and Gluma Bond Universal, with no significant difference between the latter two. After aging, Gluma Bond Universal and G2-Bond Universal revealed significantly greater bond strength to caries-affected dentin when applied in the self-etch protocol than in the etch-and-rinse protocol. No significant differences were detected among adhesives when the etch-and-rinse protocol was used, regardless of testing time and substrate. CONCLUSIONS: Phosphoric acid pre-etching negatively affected the bonding performance of Gluma Bond Universal and G2-Bond Universal to caries-affected dentin.