Effect of home bleaching agents on the hardness and surface roughness of resin composites

ABSTRACT

Ten percent carbamide peroxide is an effective, safe home bleaching agent. Higher concentrations are more effective, but there are mixed reports on their hardness and surface roughness effects on resin composites. To evaluate the effect of home bleaching agents; Opalescence Now 10% carbamide peroxide (Ultradent Products, USA) and Perfect Bleach 17% carbamide peroxide (Voco, Germany) on the surface hardness of microhybrid resin composites; Filtek Z250 (3M ESPE, USA) and Point 4 (Kerr, USA) and their surface roughness of selected treatment. Thirty specimens were prepared using acrylic moulds (4mm diameter x 2mm thick). N=5 controls placed in distilled water for 14 days. N=5 treated with Opalescence, and n=5 treated with Perfect Bleach for 2 hours every day for 14 days. Surface hardness was tested using Vickers hardness tester FV-7 (Future Tech Corp, Japan). Data analyzed with Mann-Whitney test with (P<0.05) considered significant. One specimen from 10% carbamide peroxide group was randomly selected for surface roughness, (Ra) evaluation using Atomic Force Microscopy (Ambios Technology, California, USA). All tested materials showed no significant changes in surface hardness after 14 days bleaching with 10% and 17% carbamide peroxide. However, AFM evaluation revealed an increase in Ra in both composites with 10% carbamide peroxide. Fourteen days bleaching using 10% and 17% carbamide peroxide did not have different effect on the surface hardness of Point 4 and Filtek Z250. The Ra increased after bleaching in both composites. The AFM surface roughness evaluation observed in 3D images shows to be a promising technique.