Effects of three different bleaching agents on microhardness and roughness of composite sample surfaces finished with different polishing techniques

Background: The aim of this study was to evaluate effects of different polishing methods and whitening agents on surface hardness and roughness of nano-hybrid composite resin.Material and Methods: In total, one hundred twenty disc-shaped specimens were prepared to nano-hybrid composite (Charisma Diamond).60 samples were used for microhardness measurements and the others were used for the evaluation of surface roughness.Samples were divided randomly into two subgroups (n = 30 each).In first group a low-viscosity liquid polishing agent (Biscover LV) was applied.In the second group, nothing was applied.All the samples were stored in distilled water at 37°C for 24 h.After initial measurements were completed, samples were divided randomly into three subgroups for bleaching application.10% carbamide peroxide (Opalescence PF), 45% carbamide peroxide (Opalescence PF Quick), 38% hydrogen peroxide (Opalescence Boost) was applied.Then microhardness and surface roughness measurements of samples were repeated and data were recorded as final values for each sample.Results: When the polishing techniques were compared, no signicant difference was observed in surface hardness and roughness.When the bleaching agents were compared, the 10% carbamide peroxide and 38% hydrogen peroxide containing bleaching agent groups showed statistically significant differences between pre-and post-procedure hardness values (p<0.05).Conclusions: Office-type bleaching agent containing CP was observed to be more secure for composite resins than other bleaching agents.No negative effect of glaze materials on the protection of surface roughness and hardness of composite resin was observed.