Effect of antioxidant/reducing agents on the initial and long-term bonding performance of a self-etch adhesive to caries-affected dentin with and without smear layer-deproteinizing

This study aimed to evaluate the effect of a reducing agent containingp-toluenesulfinic acid sodium salt (Accel (R)) and plant-extract antioxidant (rosmarinic acid solution) on the bonding durability of a self-etch adhesive to caries-affected dentin with and without smear layer-deproteinizing with NaOCl solution. The caries-affected dentin were assigned to pretreatment of smear layer-deproteinizing with NaOCl solution or none, then subdivided to reducing agent/antioxidant treatment with p-toluenesulfinic acid sodium salt or rosmarinic acid solution or none. After bonding with 2-step self-etch adhesive and restoring with resin composite, the specimens were stored in artificial saliva for 24 h or 1 year. The microtensile bond strength (mu TBS) were analyzed by threeway ANOVA with post-hoc Tukey's test and t-test (p < 0.05). The collagen-fibril status at hybridized complex was observed under TEM. The results showed that mu TBS to caries-affected dentin significantly decreased after 1-year of storage (p < 0.05). Smear layer-deproteinizing with NaOCl significantly decreased mu TBS to caries-affected dentin despite eliminating hybridized smear layer, however a subsequent application with p-toluenesulfinic acid sodium salt and rosmarinic acid solution significantly increased initial bond strengths (p < 0.05) and maintained the bond strengths after 1-year of storage (p > 0.05), with preservation of collagen-fibril integrity within authentic hybrid layer. Therefore, the additional application of p-toluenesulfinic acid sodium salt and rosmarinic acid solution after smear layer-deproteinizing with NaOCl could improve initial and long-term bond strengths of a self-etch adhesive to caries-affected dentin.