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

Abstract 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: Δ 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 p 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 E *) and gloss changes caused by bleaching treatments. Conclusions After 2-week bleaching cycles, composites showed significant gloss reduction ( p E *