PurposeWound closure technique is an operative factor that influences early post-operative complications after third molar surgery. This study investigates and compared the effectiveness of two closure techniques, primary closure and healing by second intention of the oblique incision on postsurgical discomfort after mandibular third molar surgery.Materials and methodsThis is a prospective, randomized, double-blind, split mouth controlled trial. Surgical sites were divided into two groups Control group received simple sutures in both alveolar crest incision and oblique incision and intervention group received simple sutures in alveolar crest incision, while the oblique incision healed by second intention. All the patients were instructed to measure pain according to visual analogue scale (VAS) in postoperative period, swelling, mouth opening was assessed at 72h and 7 days after surgery. The wound healing was assessed on day 7.ResultsThirty-five patients, who had bilateral impacted third molars of similar surgical difficulty, were recruited. Thirty-one successfully completed the study. Patients in the second intention group had significantly less pain at 24h (p < 0.27). and 48h (< 0.001), had significantly less swelling (< 0.001) and trismus (< 0.001) and patients submitted to primary closure had a better evaluation of the Landry index (p < 0.001).ConclusionHealing by second intention of the oblique relaxing incision by partial surgical wound closure, in our study, were superior to the primary closure in reduction of post-operative pain, swelling and trismus.Trial registrationThis trial is registered at Brazilian Registry of Clinical Trials–ReBEC -UTN: RBR-5fxbqsf (https://ensaiosclinicos.gov.br/rg/RBR-5fxbqsf).