Silorane and dimethacrylate-based composites and bleaching agents

Objectives: This study evaluated the effects of two different bleaching agents (whiteness HP-FGM-Brasil and Whiteness Perfect-FGM-Brasil) with two different methods :in-office system: 35% hydrogen peroxide (HP) and home system: 16% carbamide peroxide(CP) on the microhardness and surface texture of 3 different  composite resins (Filtek Z250, 3M ESPE, St Paul, MN,EUA - methacrylate  based-resin,micro hybrid (FZ); Filtek Supreme, 3M ESPE, St Paul,MN, EUA – methacrylate-based nano hybrid (FSU);  Filtek silorane, 3M ESPE, St Paul, MN,EUA - silorane micro hybrid (FSI)). Methods: Ten specimens were made of each resin and randomly divided into 2 groups (A and B) equally (n=5). The appropriate bleaching procedure was performed on the top surface of test group. The Vickers hardness (VHN) measurements were performed at the top surface before and after the bleaching procedure.One specimen of each group was investigated in scanning electron microscope and EDX. Results: The data were analyzed with two-way Analysis of Variance (ANOVA) and Tukey test. Statistical significance difference among the microhardness of the tested composite groups was detected. After exposure to both bleaching agents the FZ showed decreased of its VHN values. The FSU was only affected when the in-office bleaching procedure was conducted. The initial VHN values of FSI were minor than FZ and  FSU. Silorane based resin,FSI, showed no significant alteration after none of the bleaching procedures. The  bleaching procedures did not cause major surface texture changes on the restorative materials. Conclusions: Within the limitations of this study,the Energy dispersive X-ray microanalysis (EDX) showed great diversity of ultrastructures of the composite resins tested, which stemmed from the different revolutionary technologies used to manufacture them. This diversity among them had an impact on its Vickers hardness before and after contact with bleaching agents.