Effect of tooth-bleaching strips on gloss and color of composites

Objectives: The purpose of this in vitro study was to evaluate the gloss and color changes of hybrid and nano-hybrid resin composites after tooth-whitening strips and carbamide peroxide bleaching gel application. Materials and methods: The resin composites used were: a hybrid (Herculite-HR, Kerr) and a nano-hybrid (Premise-PR, Kerr), A2 shade and the bleaching agents: 10% carbamide peroxide bleaching gel (Nite White-NW, Discus Dental); 6.0% (Crest Whitestrips Classic-Cs, Procter&Gamble) and 14% hydrogen peroxide strips (Crest Whitestrips Supreme-Ss, Procter&Gamble). Three groups of disk-shaped (10x1mm thickness) specimens per resin composite were prepared (n=8), which were subjected bleaching treatment with the three agents evaluated, for two weeks, according to their respective protocols. Surface gloss and color (CIE-L*a*b* system) measurements were performed before (baseline) and after bleaching applications. Gloss changes were expressed as % value differences and color changes were assigned as ÄE relative to the baseline measurements. Statistical analysis of the % gloss differences and ÄE values were performed by two-way Anova and Sheffe's tests (a=0.05). Results: The gloss change (%) and ÄE values were, accordingly: HR-NW 45,6±7,1/1,0±0,3; HR-Cs 49,2±5,4/1,2±0,3; HR-Ss 50,6±4,2/0,8±0,2; PR-NW 29,6±5,8/1,9±0,7; PR-Cs 50,0±3,9/1,2±0,3; PR-Ss 41,7±4,1/1,4±0,2. Regarding gloss, Herculite revealed higher changes compared to Premise after NW gel and Ss application; Ss and Ps caused higher effect on Premise relative to NW, whereas no differences were established for Herculite. In respect to color, NW and Ss induced higher ÄE changes in Premise compared to Herculite; treatment of Premise with NW provided higher color changes than Cs and Ss. Conclusions: All bleaching agents provided gloss and color changes on the resin composites evaluated. More aggressive effect was noted on gloss than on color changes for both resin composites. The degree of the influence on gloss and color parameters is resin composite- and bleaching agent-depended.