The effect of photobiomodulation on total amount of substance P in gingival crevicular fluid: placebo-controlled randomized clinical trial.

To investigate the effect of photobiomodulation (PBM) and placebo on total amount of substance P in gingival crevicular fluid (GCF) pre- and postoperatively. Twenty-six patients having tooth with symptomatic apical periodontitis were enrolled in this study. GCF was collected preoperatively. The patients were assigned into two groups (n = 13), as follows: placebo and PBM. Sampling was repeated 7 days after root canal treatment. Two independent samples T test was used for analyzing of the differences between preoperative and postoperative substance P levels in GCF (p = .05). The Pearson correlation analysis was used for determination of correlation among substance P levels and other variables. For placebo group, there is no significant difference between preoperative and postoperative total amounts of substance P level (p = 0.553). For PBM group, postoperative total amount of substance P level was significantly higher than those of preoperative level (p = 0.005). Within the limitation of the present study, PBM has immunomodulation effect linked to the modulation of the total amount of substance P in the gingival crevicular fluid. Thai Clinical Trials Registry: TCTR20161228002.