Influence of Different Cavity Disinfection Protocols on Adhesion at the Resin Composite–Dentin Interface

This study evaluated the effects of four cavity disinfection protocols on microtensile bond strength (µTBS) and failure mode of dentin bonded with a universal adhesive in self-etch mode. Sixty human third molars were assigned to five groups (n = 12): Control (Clearfil S3 Bond Universal), Clearfil SE Protect Bond (CPB, MDPB-containing), 2% chlorhexidine (CHX), 5.25% sodium hypochlorite (NaOCl), and 200 ppm hypochlorous acid (HOCl). After disinfectant application and bonding, composite build-ups were sectioned into beams (≈0.9 mm2) and tested as immediate (24 h) and thermocycled (10,000 cycles) subgroups. Data were analyzed using two-way ANOVA, Tukey HSD, and chi-square/Fisher’s exact tests (α = 0.05). At 24 h, NaOCl and CHX produced significantly lower µTBS than the control, HOCl, and CPB groups (p < 0.05). After thermocycling, Control, CPB, and NaOCl declined significantly, while CHX remained stable (p = 0.960) and HOCl showed non-significant reduction (p = 0.086). NaOCl yielded the highest adhesive failure rate and lowest bond strength. CHX reduced initial µTBS but maintained stability. HOCl and CPB produced values comparable to controls, though HOCl was more aging-susceptible. MDPB-containing adhesives may preserve bond durability while providing disinfection.