Effect of Photobiomodulation on Salivary Nitrite in Patients with Chemotherapy-Induced Oral Mucositis: A Randomized Clinical Trial.

Background: Oral mucositis (OM) is a severe inflammatory and ulcerative condition of the oral mucosa commonly induced by chemotherapy. Photobiomodulation (PBM) therapy has been proposed for preventing and treating OM. However, the understanding of light interaction with biological tissues and the variability in light sources and protocols limit its widespread application. This study aimed to evaluate the impact of PBM on salivary nitrite levels, a marker of oxidative stress associated with inflammation and tissue damage. Materials and Methods: This prospective, randomized, double-blind clinical trial included 45 patients, evenly divided into three age- and sex-matched groups. Group 1 received basic oral care instructions prior to chemotherapy. Group 2 received these instructions plus PBM using a 650 nm intraoral diode laser. Group 3 received basic oral care instructions combined with PBM using both a 650 nm intraoral diode laser and a 980 nm extraoral diode laser. OM severity was assessed using World Health Organization criteria, and salivary nitrite levels were measured using the Griess reagent kit (Biotium®) according to the manufacturer's instructions 1 and 2 weeks after the first chemotherapy session. Results: Our study included 45 patients who were evenly distributed into three groups, matched for age, sex, tumor type, and type of chemotherapy. Significant differences in OM severity were observed among the groups at both 1 and 2 weeks (p = 0.000). Salivary nitrite levels also showed significant differences between groups at these time points (p = 0.00). Significant differences were found between the control group and both laser treatment groups, but no significant difference was noted between the two laser treatment groups. Conclusions: PBM effectively reduces OM severity, whether used intraorally alone or combined with extraoral application. This effect is likely due to PBM's ability to lower salivary nitrite levels, indicating reduced oxidative stress and inflammation.