In this study, photobiomodulation with low-level laser therapy (PBM-LLLT) along with potassium nitrate (KNO₃) significantly reduced sensitivity after bleaching as compared to the control group; but, no synergistic effect between these treatments was observed for the different evaluation periods. Both the desensitizing agents investigated reduced sensitivity after bleaching with 35% hydrogen peroxide.

To examine the effect of photobiomodulation with low-level laser therapy (PBM-LLLT) combined with 5% potassium nitrate (KNO₃) on controlling tooth sensitivity (TS) following in-office tooth bleaching.

Based on the inclusion and exclusion criteria in this clinical, randomized, controlled, double-blind, and split-mouth study, 50 volunteers were selected. These volunteers were randomly assigned to four groups namely, G1 (control): placebo gel application, 35% hydrogen peroxide bleaching (HP35) and mock PBM-LLLT without light emission; G2: placebo gel application, bleaching with HP35 and PBM-LLLT; G3: application of KNO₃, bleaching with HP35 and mock PBM-LLLT; and G4: application of KNO₃, bleaching with HP35 and PBM-LLLT. Pain assessment questionnaire helped to determine the TS during the 21 days of treatment. The Friedman test was used to determine intragroup analysis, and the Wilcoxon and Mann-Whitney tests were used for intergroup comparisons.  

The intragroup evaluation portrayed significant differences among the evaluation times in all the groups (p ≤ 0.05). The highest pain sensitivity levels were noted on the 1st, 8th, and 15th days. In G1, TS manifested for up to 3 days following each bleaching session, whereas G2, G3, and G4 presented TS only on the days of the bleaching sessions. The intergroup analysis depicted that TS manifestation varied significantly between G1 and the other groups (p ≤ 0.05) but did not differ significantly among G2, G3, and G4 (p ≥ 0.05).  

PBM-LLLT and KNO₃ are effective at minimizing pain sensitivity after tooth bleaching. Although, there was no synergistic effect between these treatments observed for the different evaluation periods.