Effect of tooth-bleaching methods on gloss and color of resin composites

Objectives: The purpose of the study was to evaluate gloss and color changes of resin composites after exposure to different bleaching agents. Methods: Products used, were: Nite White ACP (10% carbamide peroxide gel), Crest Classic and Supreme Whitestrip (6.5% and 14% hydrogen peroxide strips, accordingly). A hybrid (Herculite XRV) and a nanohybrid (Premise) resin composite were exposed to the bleaching agents. Twenty-four disk-shaped specimens per composite were subjected to bleaching by each of the agents (n = 8) for up to 2 weeks. Color changes using CIE-L*a*b* system (50:50% acceptability threshold: Delta E* = 3.3) were recorded after 1 and 2 weeks bleaching cycles relative to baseline measurements. In addition, gloss measurements (in gloss units) were performed at the same bleaching intervals and gloss changes were calculated. Results: All bleaching agents tested provided decrease in gloss of both composites after 2-week bleaching (p < 0.05). No differences were detected among the three bleaching regimens, for up to 2-week application, in terms of color and gloss changes on both composites. After the 2-week bleaching period, hybrid composite presented higher gloss reduction (%) than nanohybrid regardless of the bleaching agent (p < 0.05). Color change (Delta E*) was lower than 3.3 for all composite-bleaching agent combinations. After 1- and 2-week bleaching time, the nanohybrid composite provided higher color change than the hybrid under all bleaching procedures (p < 0.05). No strong correlation was proved between color (Delta E*) and gloss changes caused by bleaching treatments. Conclusions: After 2-week bleaching cycles, composites showed significant gloss reduction (p < 0.05). Color alteration was below the 50:50% acceptability threshold (Delta E* < 3.3) and it was product-depended. There was no significant difference in color and gloss changes between the evaluated bleaching strips and 10% carbamide peroxide gel. (C) 2010 Published by Elsevier Ltd.