To compare the bleaching efficacy and tooth sensitivity (TS) of 4% hydrogen peroxide (HP) in adults using a continuous or fractioned protocol.

Methods and Materials

A single-blind randomized controlled trial with a parallel design was conducted. Eighty-six patients with upper canines A2 or darker were submitted to bleaching with 4% HP gel for three weeks after random allocation into the fractioned protocol (two 30-minute daily applications) or continuous protocol (single one-hour application). We evaluated the color change at baseline, weekly, and 30 days after the bleaching using Vita Classical and Vita Bleachedguide using the units of shade guides (SGU) and by spectrophotometer using CIELab 1976 (ΔEab) and CIEDE 2000 formulas (ΔE00), as well as Whiteness Index (ΔWID). We assessed the absolute risk of TS with a visual analog scale (VAS) and numeric rating scale (NRS). Color changes in each recall were compared with the Student t-test. The risk of TS was evaluated by the Chi-square test, and the intensity by Mann–Whitney test (NRS) and Student t-test (VAS).


The mean difference for the ΔSGU Vita Classical (0.5; 95% CI: −0.5 to 1.5), ΔSGU Vita Bleachedguide (−0.4; 95% CI: −1.5 to 0.7), ΔEab (1.4; 95% CI: −0.1 to 2.9), ΔE00 (0.6; 95% CI: −0.4 to 1.6), and ΔWID (−3.2; 95% CI: −7.3 to 0.9) after three weeks of bleaching was not clinically or statistically significant (p>0.10). The absolute risk of TS was 44% (95% CI: 30–58%) and 46% (95% CI: 32–61%) in the fractioned and continuous protocols, respectively (RR=1.0; 95% CI: 0.6 to 1.5; p>0.91).


A fractioned bleaching protocol with 4% HP (30 minutes twice daily) did not increase the whitening degree nor affect the risk and intensity of TS when compared with the one-hour continuous protocol.

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