Degradation of resin–dentin bonds using NaOCl storage

Objectives. Several recent studies have reported collagen hydrolysis within bonds over the long-term. This may be one reason for the degradation of the bonds. This study therefore aimed to determine the effects of NaOCl on adhesive system bonds (total-etch bonding system vs. self-etching primer system) to dentin in order to accelerate the durability testing. Methods. Resin–dentin bonded specimens were produced using Liner Bond 2V (Kuraray), a self-etching primer system, and OptiBond SOLO (Kerr), a total-etch bonding system, according to the manufacturersʹ instructions. The bonded specimens were serially sectioned in both x and y directions across the adhesive interface to obtain beams (adhesive area: 0.9 mm2). The specimens were immersed in 10% NaOCl solution for 1–5 h after being stored in water at 37 °C for 24 h. Control specimens were tested without exposure to NaOCl. After storage, micro-tensile bond tests were performed. Results were analyzed by two-way ANOVA and Fisherʹs PLSD tests (p<0.05). All fractured surfaces were observed by SEM, and examined using an image analyzer. Results. The bond strengths decreased with increasing storage time in NaOCl. Fractography showed that NaOCl had a greater effect on the bond structure of OptiBond SOLO than on that of Liner Bond 2V, although both adhesives were susceptible. Significance. Deterioration of the bonds was responsible for the effect of NaOCl on the hybrid layer. This deterioration may occur in humans in cases of deproteinization within the bonds.