Effect of In-Office Bleaching on New and Stained Resin Composites

Purpose: The effect of in-office bleaching on whitening of newly-placed or discolored composite resin restorations is controversial. The purpose of this study was to determine color changes of composites when subjected to light- and chemically-activated in-office bleaching. Methods: 12 Discs 15mm in diameter and 2mm thick were fabricated from each of 2 shades (A2 & A4) of 2 composites: microfilled composite (Durafil VS - Heraeus Kulzer) (DF) and micro-hybrid composite (TPH3- Dentsply Caulk) (TPH). Four groups (DF-A2, DF-A4, TPH-A2 and TPH-A4) were subdivided into 3 subgroups (n=4) and specimens were polished, placed in distilled water for 24h at 37°C before subjected to bleaching/staining/bleaching routine. Bleaching was performed using Beyond (Beyond Technology Corp), LumaWhite-Plus (LumaLite, Inc.) and Opalescence-Boost (Ultradent Products, Inc.) in-office bleaching systems according to manufacturers' recommendations with light-activation where indicated. Staining was achieved by immersing in coffee solution for 48h at 37°C. Colorimetric measurements were performed at baseline, after bleaching, after staining then after second bleaching using Chroma-meter CR-300 (Minolta). Changes from baseline were calculated and statistically-analyzed using ANOVA. Results: None of the bleaching systems notably changed the color of any of composites tested (delta-E<2). Generally the microfilled resin composite groups showed more staining than the micro hybrid resin groups. Stained resin composites showed different degrees of whitening with no significant color change observed with TPH (delta-E<2) and significant changes (p<.012) ranging from delta-E 2.7 to delta-E 4.1 were observed with DF only with Beyond and LumaWhite but not with Opalescence. Conclusions: DF showed more color change than TPH when immersed in coffee. Stained resin composites showed different degrees of whitening with no significant color change observed with TPH and significant changes observed with DF only with Beyond and LumaWhite but not with Opalescence. Acknowledgments: Egyptian Ministry of Higher Education, Dentsply, Kulzer, Beyond, Lumalite and Ultradent.