The Effect of Different Concentrations of Carbamide Peroxide Bleaching Gel on Shear Bond Strength of a Bonded Nanocomposite to Enamel and Dentin

Although bleaching is an effective way in creating a beautiful smile, there is a controversy about the effectiveness of bleaching agents on composite restored teeth. Therefore, this study aimed to evaluate the effect of carbamide peroxide (CP) at different concentrations on shear strength (SS) of a bonded nanocomposite to enamel and dentin.
Material and In this in-vitro study, 96 premolar teeth were divided into two groups. Buccal surfaces were abraded to reach enamel or dentin surfaces. The specimens were mounted in acrylic cubs and bonding procedures were performed using Single Bond 2. A composite cylinder was formed on surfaces using Z350 nanohybrid composite and then, the specimens were divided into four subgroups: 1: the control; 2, 3, and 4 bleached with Opalescence PF 10, 15, & 20% in 8, 6, & 4 hours a day, respectively. The SS were measured and the data were analyzed using one-way ANOVA followed by Tukey multiple comparisons test.
There was a reduction in SS in both groups after bleaching. This reduction was not statistically significant in the enamel subgroups (P=0.589), but it was statistically significant in the dentin subgroups. This significance was only between the control and fourth subgroups (P=0.005).
According to this study, if bleaching with CP is performed on a nanocomposite restoration with dentinal margins, replacing the restoration should be taken in to consideration. Increasing the CP concentration leads to more deterioration of dentinal bond. Enamel bond is less affected.