Effects of photobiomodulation on nociceptor activity and the expression of proinflammatory cytokines after temporomandibular joint disc injury in rats.

PURPOSE: Temporomandibular disorder (TMD) pain originates from muscular or intracapsular disorders, with the latter being represented by arthralgia. The aim of this study was to investigate the effects of photobiomodulation therapy (PBMT) on nociceptor activity, proinflammatory cytokine expression, neuropeptide expression, and tissue alterations in temporomandibular joint (TMJ) discs following unilateral injury in rats.

METHODS

Disc injury was induced via surgical access to the TMJ under general anesthesia. Forty rats were divided into four groups (n = 10 each). Group 1: surgical injury to the articular disc with PBMT; Group 2: sham surgery with PBMT; Group 3: surgical injury to the articular disc without PBMT; and Group 4: naïve (control). Ten PBMT sessions were conducted with a GaAs laser at a wavelength of 904 nm and an energy density of 6 J/cm². TMJs were analyzed for histological and histomorphometric parameters to evaluate tissue changes and protein levels of substance P (SP), transient receptor potential vanilloid 1 (TRPV-1), calcitonin gene-related peptide (CGRP), interleukin-6 (IL-6), interleukin-1 beta (IL-1β), and tumor necrosis factor-alpha (TNF-α). Statistical analysis was performed by ANOVA with Tukey's post-hoc test (p < 0.050 indicating a significant difference).

RESULTS

The results revealed increased expression of SP, TRPV-1, CGRP, IL-6, IL-1β, and TNF-α following TMJ injury, with significantly lower levels after PBMT than in the other groups, leading to an improvement in the initial phases of tissue repair.

CONCLUSION

These findings suggest that PBMT effectively modulates nociceptive activity and reduces proinflammatory cytokine expression, optimizing tissue regeneration and improving the treatment of TMD.