Evaluation of the dentin bonding stability of fluoride-containing universal adhesives

Aim: This study aimed to evaluate the effects of fluoride-containing universal adhesives applied with self-etch (SE) and etch-and-rinse (E&R) strategies on the adhesive–dentin interface, both immediately and after different ageing protocols, using microtensile bond strength (µTBS) data. Material and Method: Sixty human molars were randomly assigned into three groups (n = 20): Clearfil Universal Bond Quick, Clearfil Universal Bond, and Zipbond Universal. Each adhesive group was further subdivided into two subgroups according to the application mode (n = 10). After the restorative procedures, the obtained dentin sticks were allocated into three subgroups based on the ageing conditions (24 h, thermocycling, and pH cycling). Following ageing, µTBS testing was performed. The degree of conversion of the adhesives was determined using ATR-FTIR spectroscopy. µTBS data were analyzed by three-way ANOVA and Tukey's HSD test, and DC data were analyzed by one-way ANOVA and Bonferroni test (α = 0,05). Results: Both the adhesive system (p = 0,001) and application mode (p = 0,007) significantly affected bond strength. Ageing protocols showed no significant effect (p> 0,05). ZBU exhibited higher bond strength compared with CBQ and CBU. At 24 h, the ZBU E&R group showed significantly higher µTBS than the CBQ E&R group. When the subtotal bond strength were evaluated, the ZBU SE group exhibited significantly higher µTBS compared to the E&R groups of CBQ and CBU. The DC value of CBQ was significantly lower compared with both CBU and ZBU. Conclusion: The application mode of universal adhesives did not create a significant difference in bond strength. Ageing protocols did not affect the dentin bond strength. The chemical composition and application strategies of fluoride-containing universal adhesives were found to exert different effects on the µTBS values measured on dentin. Key Words: Adhesion, DC, SEM, Sodium Fluoride, Universal Adhesive, μTBS