Randomized clinical trial of two tooth bleaching agents: 2-year follow-up

Objectives: The aim of this double-blind, randomized clinical trial was to evaluate the longevity of the whitening effect (2-year follow-up) of two at-home tooth bleaching agents. Methods: Ninety-two volunteers with shade mean C1 or darker for the six maxillary anterior teeth were randomized into two groups (n= 46) according to carbamide peroxide concentration: 10% (CP10) or 16% (CP16). The treatment involved the use of the whitening agent in a tray for two hours/day during three weeks. Shade evaluations were done with a shade guide, and a spectrophotometer at baseline, and at 1-week, 6-month, 1-year and, 2-year post-bleaching. Volunteers for both treatment groups had to answer a questionnaire related to diet and oral hygiene behavior. Results: Eighty-one (88%) of the original 92 subjects enrolled in the study were recalled at 2-year follow-up and, the tooth shade remained significantly lighter than at baseline, in both treatment groups, considering the tooth shade median values (p< 0.001) or the color parameters: L*a* (p< 0.005) for CP10 group and L*b* for CP16 group (p< 0.001). Volunteers from CP10 and CP16 reported a consumption of beverage and food stains as high as at 6-month and 1-year recalls and, this consumption was not statistically significant between groups (p> 0.5). Conclusions: At 2-year post-bleaching, both treatment groups remained lighter than at baseline evaluation and, the whitening effect regression could not be observed when compared to 1-week post-bleaching.