Microtensile bond strength and bond durability of resin composite to dentin pretreated with chlorhexidine, dimethyl sulfoxide, and trans-cinnamaldehyde

Background: Despite successful immediate dentin bonding, its stability remains challenging due to its susceptibility to protease-induced degradation. Aim: This study aimed to comparatively evaluate microtensile bond strength (μTBS) of resin composite to dentin pretreated using 2% chlorhexidine (CHX), 0.05% trans-cinnamaldehyde (TCA), their combination (2% CHX/0.05% TCA) and 50% dimethyl sulfoxide (DMSO) immediately (24 h) and after long-term aging (6 months) under in vitro conditions. Materials and Methods: Superficial dentin was exposed in 75 extracted human molars. Following etching with 37% phosphoric acid, the specimens were randomly allocated ( n = 15) according to the pretreatment agent used. Universal adhesive (Single Bond Universal, 3M ESPE, St. Paul, USA) was utilized in etch-and-rinse mode and resin composite (4 mm) was built in two increments. From each tooth, dentin-composite beams (1 mm × 1 mm) were sectioned, exposed to tensile load at a crosshead speed of 0.5 mm/min to evaluate immediate and long-term μTBS. Data was analyzed statistically by Kruskal–Wallis and Wilcoxon signed-rank test ( P < 0.05). The failure modes were verified with a stereomicroscope (×40). Results: At 24 h, DMSO showed significantly higher mean μTBS than CHX ( P < 0.05). Following aging, DMSO remained the highest while the mean μTBS of control was significantly lower than CHX and CHX/TCA ( P < 0.05). Intragroup comparisons showed that μTBS decreased over time in control and increased in CHX ( P < 0.05). Conclusion: Within the limits of this study, DMSO pretreatment significantly improved both the immediate and long-term μTBS of composite to dentin.