Photobiomodulation (PBM) is a therapy that stimulates repair, pain relief, and reduces inflammation. The aim of this study is to evaluate the effectiveness of a new PBM protocol in the treatment and pain relief of RAS lesions.

Recurrent aphthous stomatitis (RAS) is the most common chronic ulcerative inflammatory disorder of the oral cavity, affecting approximately 20% of the general population, with no gender predilection. Its etiopathogenesis remains undefined, although factors such as local trauma and syndromes like Behcet's syndrome are implicated in predisposition. RAS manifests in three distinct clinical presentations, with the smallest being the most common, accounting for 80% of cases. Minor RAS present as round or oval ulcers, smaller than 1 cm, covered by a grayish-white pseudomembrane, commonly occurring on non-keratinized mucosa such as lips, buccal mucosa, and floor of the mouth. Photobiomodulation (PBM) is a therapy that stimulates repair, pain relief, and reduces inflammation. The aim of this study is to evaluate the effectiveness of a new PBM protocol in the treatment and pain relief of RAS lesions. The study is a randomized, triple-blind, placebo-controlled clinical trial to be conducted at the Hospital de Clinicas de Porto Alegre (HCPA) in Rio Grande do Sul, from March 2023 to December 2025. Thirty-four patients of both genders will be selected and randomly allocated into three groups: 17 patients in the PBM treatment group with 4.5J and 17 patients in the control group. Inclusion criteria are patients over 18 years old with at least one painful ulcer in the mouth. If the patient has more than one ulcer, all will be treated. Exclusion criteria include patients who have undergone previous treatment for RAS, patients with asymptomatic ulcers, and patients with any systemic condition related to RAS - for example, Behçet's Syndrome, Periodic Fever Syndrome, Aphthous Stomatitis, Pharyngitis, and Cervical Adenitis, HIV infection. The study outcome is lesion healing, and the independent variables analyzed in the study will be: pain, lesion size, and difficulty in eating, drinking, and brushing teeth due to the presence of RAS. These variables will be collected through questionnaires administered during all patient visits. Analyses will be performed using PASW 18.0 software. Initially, data distribution will be assessed using Shapiro-Wilk and Kolmogorov-Smirnov tests. If the data show normal distribution (p>0.05), the t-test will be used. If the distribution is non-normal (p<0.05), the Wilcoxon test will be employed. The significance level (p-value) will be set at 5%.

Inclusion Criteria:

• Patients over the age of 18
• Patients presenting at least one painful mouth ulcer (minor ulcer), located on the tongue, jugal mucosa or labial mucosa, starting on the same day or the day before.

Exclusion Criteria:

• Patients who have already undergone other treatment for RAS;
• Patients with asymptomatic ulcers;
• Patient must not be undergoing or have undergone any treatment for RAS;
• Patients with any systemic condition related to RAS - e.g. Behcet's Syndrome, Periodic Fever Syndrome, Pharyngitis and Cervical Adenitis, HIV infection.

All collected IPD

After publication of the outcomes, for one year

If formally requested and referenced by the interested researcher

The participant, examiner and outcomes assessor will not know which group has been allocated (triple-blind). Another person (the applicator) will carry out the randomization and know which group the patient belongs to.