The purpose of this study was to examine the effect of hydrogen peroxide at different application time and concentrations on the microtensile bond strength of resin restorations to the deep and the pulp chamber dentin.

A conventional endodontic access cavity was prepared in each tooth, and then the teeth were randomly divided into 1 control group and 4 experimental groups as follows: Group 1, non treated; Group 2, with 20% Hydrogen peroxide(H₂O₂); Group 3, with 10% H₂O₂; Group 4, with 5% H₂O₂; Group 5, with 2.5% H₂O₂; the teeth of all groups except group 1 were treated for 20, 10, and 5min. The treated teeth were filled using a Superbond C&B (Sun medical Co., Shiga, Japan). Thereafter, the specimens were stored in distilled water at 37℃ for 24-hours and then sectioned into the deep and the chamber dentin. The microtensile bond strength values of each group were analyzed by 3-way ANOVA and Tukey post hoc test(p < 0.05).

In this study, the microtensile bond strength of the deep dentin (D1) was significantly greater than that of the pulp chamber dentin (D2) in the all groups tested. The average of microtensile bond strength was decreased as the concentration and the application time of H₂O₂ were increased. Analysis showed significant correlation effect not only between the depth of the dentin and the concentration of H₂O₂ but also between the concentration of H₂O₂ and the application time(p < 0.05), while no significant difference existed among these three variables(p > 0.05). The higher H₂O₂ concentration, the more opened dentinal tubules under a scanning electron microscope(SEM) examination.