Effect of Bleaching on Surface Roughness of Composites

Objectives: This study evaluated the effect of home and office bleaching agents on surface roughness of microhybrid and nanofilled composite resins.

Methods: Point 4 (Kerr, USA) microhybrid composite, Premise (Kerr, USA) and Filtek Supreme (3M ESPE, USA) nanofilled composites were selected. Fifty samples of each composite were prepared in acrylic molds under clear matrix strips and polished. For each composite five groups(n=10) were defined as: control, two weeks home bleaching, 4 weeks home bleaching, one time office bleaching and two times office bleaching with 2 weeks interval. Opalescence PF (Ultradent, USA) with 20% carbamide peroxide and Opalescence Quick (Ultradent, USA) with 35% carbamide peroxide were used as the home and office bleaching agents respectively. After performance of bleaching procedures, all the specimens of bleached and control groups were subjected to roughness testing (Ra) using a profilometer. The data were analyzed with two-way ANOVA statistical test (P<0. 05). Surface topography of selected specimens was assessed by Scanning Electron Microscopy. Results: The mean values of surface roughness (Ra) in control, 2 weeks home bleaching, 4 weeks home bleaching, one time office bleaching, two times office bleaching for Point 4 were: 0.092± 0.025, 0.085± 0.012, 0.092 ± 0.024, 0.089 ± 0.010, 0.095 ± 0.030 micrometers respectively. These values for Filtek Supreme were: 0.087± 0.026, 0.093± 0.020, 0.096 ± 0.019, 0.100 ± 0.019, 0.100 ± 0.017 micrometers, respectively. Also these values for Premise were: 0.088± 0.015, 0.089± 0.019, 0.104 ± 0.031, 0.093 ± 0.017, 0.095 ± 0.026 micrometers, respectively. There was no significant difference in surface roughness values among all groups (P>0.05). None of composites showed crack or surface changes after bleaching.

Conclusion: The bleaching agents used in this study had no significant effects on surface roughness values and surface topography of two types of nanofilled composites and one type of microhybrid composite.