Objective: The aims of this study were to evaluate whether the use of a dentifrice containing 5% potassium nitrate (KNO 3 ) prior to and during in-office dental bleaching reduces bleaching-induced tooth sensitivity and affects bleaching efficiency.Materials and methods: Thirty-eight individuals were randomly distributed into two groups (n = 19). The experimental group performed toothbrushing using a dentifrice containing 5% KNO 3 , one week before treatment and before the first and second bleaching sessions. In the control group, a placebo dentifrice without KNO 3 was applied as described for the first group. Tooth sensitivity was recorded on visual analog scales (VAS) and numeric rating scales (NRS) immediately and up to 48 h after bleaching sessions. Color change at different time intervals, was evaluated with shade guide units (ΔSGU) and a digital spectrophotometer (ΔE CIELab 1976 and CIEDE2000) at baseline and 7, 15, and 30 days post-bleaching. Mann-Whitney test and t-test were used to evaluate TS intensity for NRS and VAS scales, respectively, and T-test was used for color difference evaluation.Results: No significant difference in tooth sensitivity's absolute risk and intensity were observed between tested groups in any evaluated treatment time for NRS (p = 0.91) or VAS scales (p = 0.48). T-test showed no significant difference in both ΔE and ΔSGU tooth color among the experimental and control groups during the different evaluation times (p = 0.27). Conclusion:The use of a dentifrice containing 5% KNO 3 does not prevent postoperatory tooth sensitivity but allows the same whitening efficiency as a regular dentifrice.Clinical significance: The use of a dentifrice-containing KNO 3 did not prevent bleaching-induced tooth sensitivity when high-concentrated hydrogen peroxide was used for in-office bleaching.