Photobiomodulation with low-level laser therapy (PBM-LLLT) and potassium nitrate (KNO3) effectively reduces pain sensitivity after tooth bleaching, but no synergistic effect between these treatments was observed for the different evaluation periods as elucidated in the journal of 'Clinical Oral Investigations.

'Brennda de Paula and researchers analysed the effect of photobiomodulation with PBM-LLLT combined with 5% KNO3 on controlling tooth sensitivity (TS) following in-office tooth bleaching.They conducted a clinical, randomised, controlled, double-blind, and split-mouth study comprising 50 volunteers based on the inclusion and exclusion criteria. They were randomly categorised into four groups: 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: use of KNO3, bleaching with HP35 and mock PBM-LLLT; and G4: use of KNO3, bleaching with HP35 and PBM-LLLT. The TS during 21 days of treatment was examined with the help of a pain assessment questionnaire. For the intragroup analysis, Friedman test was used. Wilcoxon and Mann-Whitney tests were used for intergroup comparisons.

The study culminated that intragroup evaluation had significant differences among the evaluation times in all groups. The 1st, 8th, and 15th days witnessed high pain sensitivity levels. In Group 1, TS manifested for up to 3 days after each bleaching session, on the other hand, Group 2, Group 3, and Group 4 exhibited TS only on the days of the bleaching sessions. As per the Intergroup analysis, TS manifestation differed significantly between G1 and other groups (p ≤ 0.05) but no significant differences among G2, G3, and G4.