SUMMARYThis double-blind randomized clinical trial evaluated the efficacy and safety of two carbamide peroxide concentrations used in at-home vital bleaching. Ninety-two volunteers with a shade mean of C1 or darker for the six maxillary anterior teeth were randomized into two balanced groups (n=46) according to bleaching agent concentration: 10% (CP10) or 16% (CP16) carbamide peroxide. The patients were instructed to use the whitening agent in a tray for two hours once a day for three weeks. Shade evaluations were done with a value-oriented shade guide and a spectrophotometer at baseline and one week post-bleaching (four-week evaluation). Tooth sensitivity was measured daily using a scale ranging from 0 (no sensitivity) to 4 (severe sensitivity). At the end of the study, the volunteers filled out a This clinical trial suggests that two carbamide peroxide concentrations, when used once a day for three weeks, were well tolerated by patients and were effective in tooth whitening. Although some tooth sensitivity occurred during treatment, this side effect was mostly mild and transient. SS Meireles • SS Heckmann • FL Leida IS Santos • Á Della Bona • FF Demarcoquestionnaire with seven questions aimed to give their opinion about the adopted treatment regimen. Both carbamide peroxide concentrations resulted in significantly lighter teeth at the fourweek evaluation compared to the baseline for all color parameters (p<0.0001) and shade median (p<0.001). There was no significant difference between the two groups in terms of shade change difference with either the spectrophotometer (p=0.1) or the shade guide (p=0.7). Also, no statistically significant difference was found in relation to ΔL* (p=0.7), Δa* and ΔE* (p=0.5). A significant reduction in yellowness (Δb*) was observed for CP16 compared to CP10 (p=0.05) in crude analysis, which disappeared after controlling for b* parameter at baseline. The group treated with CP16 experienced more tooth sensitivity during the first (p=0.02) and third (p=0.01) weeks of treatment compared to the CP10 group. However, no major difference was observed (p=0.09) when the degree of tooth sensitivity between groups was compared. Both 10% and 16% carbamide peroxide concentrations were equally effective and safe for a three-week at-home tooth-bleaching treatment.