The Effect of in Office Bleaching on Free Surface Energy of Siloran and Methacrylate-Based Composite Resins

Bleaching materials may influence the physical properties of resin composite restorations such as surface free energy. High surface free energy causes plaque accumulation and is an important factor for adhesion of bacteria to surfaces. The purpose of this study was to compare the surface free energy of Methacrylate-based Resin Composites with Silorane-based Resin Composites after bleaching. In this in vitro study, 48 samples of composite resin in the form of disks (8 mm diameter and 2 mm thickness) were prepared and divided into 4 groups (n=12). Samples of each group were in-office bleached with 35% hydrogen peroxide (three sessions of 45 minute, one week apart). The surface free energy (dyne cm-1) was measured with Angle Measuring System. Data were analyzed by one way ANOVA, Tukey and paired t-test at the significance level of 0.05. The mean and standard deviation of the surface free energy of P90, Z250, Z250 XT and Z350 XT composites after bleaching, were 50.09±6.22, 52.48±5.50, 61.38±4.62 and 54.59±2.41, respectively. Paired t-test analysis showed that there was no significant difference after bleaching in all composites except Z250 (P<0.05). Bleaching with 35% hydrogen peroxide caused a significant increase in the surface free energy of P90, Z250 XT and Z350 XT composites, but caused no significant difference in the composite Z250.