RESUMO
PURPOSE: The aim of the present study was to compare the effect of intraoral (IO) and extraoral (EO) diode laser irradiation on oral mucositis (OM) induced by 5-fluorouracil (5-FU) in rats. METHODS: Animals (n = 78) were divided into the following groups: negative control (NC), positive control (PC), IO 6 J/cm2, EO with 6 J/cm2 (EO 6 J/cm2), and 12 J/cm2 (EO 12 J/cm2). OM was induced with an intraperitoneal injection of 5-FU and scarification of the buccal mucosa. Over the following 14 days, animals received photobiomodulation (PBM) daily. Clinical and histological evaluation was done by scores at days 8, 10, and 14. The redox state was evaluated by reactive species levels, antioxidant network, and immunohistochemistry analysis. RESULTS: Clinically, on day 8, PBM groups showed lower scores of OM with EO 6 J/cm2 presenting a significantly lower degree compared to PC (p < 0.05). On days 10 and 14, all PBM groups exhibited improvement of OM compared to PC (p < 0.01). On day 8, all PBM groups exhibited an accelerated healing process compared to PC (p < 0.01) and reduction of reactive species (p < 0.001). Also, all PBM groups demonstrated higher levels of antioxidant GPx compared to PC (p < 0.001). Analysis of nitrotyrosine revealed that on day 14, this protein damage marker was significantly reduced in the EO 6 J/cm2 group (p > 0.05). CONCLUSIONS: An EO diode laser protocol promoted positive effects in the clinical, histopathological, and redox state in OM induced by 5-FU in rats. Among the EO protocols, EO 6 J/cm2 showed the most encouraging results.