OBJECTIVES: To assess the impact of photobiomodulation therapy in pain, facial oedema, and trismus mitigation in the postoperative period after lower third molar extractions. METHODS: We conducted a comparison between active photobiomodulation and simulated photobiomodulation after both lower third molars extraction in the same patients, within a double-center clinical trial. The role of photobiomodulation was evaluated based on pain, measured using the VAS scale. Oedema and trismus, assessed through millimetric measurements. Additionally, analgesic consumption was monitored during the 7-day's postoperative period. The study adhered to the CONSORT checklist and was registered on the ClinicalTrials (NCT05255731). The Levene test was used to assess precision (α=0.05), and statistical analysis was performed using Jamovi software. Paired t-tests or the Wilcoxon test were employed to analyze the primary and secondary outcomes. RESULTS: The study included 83 patients and 166 randomization units. The study group showed a significant reduction in pain at all evaluation times (P <
.01), as well as reductions in facial oedema and trismus on postoperative days 2 and 7 (P <
.01). A significant difference in analgesic use was observed on all days, except on the seventh postoperative day. CONCLUSION: The photobiomodulation protocol, using an 808 nm, 100 mW Ga-Al-As diode laser, applied both intraorally and extraorally in a single 30 seconds (3 Joules/per point) postoperative session, significantly reduced pain, oedema, and trismus following mandibular third molar extraction, particularly on postoperative days 2 and 7. CLINICAL SIGNIFICANCE: Photobiomodulation can be an effective complementary therapy for reducing pain, facial oedema, and trismus in patients after lower third molar extraction.