الفهرس 
Introduction
BLEACHINGOnly 14 pages are availabe for public view
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Abstract
Objectives: The purpose of the present study was to evaluate the effect of different concentrations of carbamide peroxide (CP) bleaching gels on surface roughness and surface hardness of silorane resin-based composite (RBC) comparing it with a methacrylate RBC. Scanning electron microscopy was used to study surface characterization before and after bleaching. Methods: Two different RBCs [methacrylate RBC (Valux Plus) and silorane RBC (Filtek P90)] were bleached with 3 CP bleaching gels (10%, 16% and 30% CP). For surface roughness and hardness, a total of 80 specimens (8 mm diameter and 2 mm thickness) were prepared (40 for each composite). Each group was equally subdivided into 4 subgroups to be immersed in distilled water (control) for 14 days, 10% and 16% CP 1h/day for 14 days and 30% CP once for 30 min. Surface roughness was measured by Surftest and surface hardness by Vickers microhardness tester. Results: of the used bleaching gels had a significant effect on the surface properties of the tested composites, except for 16% CP which caused significant increase in surface roughness for Valux Plus. This was supported by SEM micrographs. Additionally, Filtek P90 had higher surface roughness and lower surface hardness values than Valux Plus for all groups. Conclusions: Carbamide peroxide bleaching gel had no significant effect on surface properties of silorane and methacrylate resin-based composites except for 16% carbamide peroxide which increased the surface roughness for methacrylate resin-based composite. Silorane resin-based composite had higher surface roughness and lower surface hardness than the methacrylate-based one.