Tehran University of Medical Sciences Journal of Craniomaxillofacial Research 2345-5489 5 3 2018 09 15 112 118 Mehrnoush Momeni Department of Oral and Maxillofacial Surgeon, Sina Hospital, Tehran, Iran; Department of Oral and Maxillofacial Surgery, School of Dental Medicine, Tehran University of Medical Sciences, Tehran, Iran. Mostafa Mortazavi Department of Oral & Maxillofacial Surgery Resident, Shariati Hospital, Department of Tehran University of Medical Sciences, Tehran, Iran. Minou Najarnobari Dentist, School of Dental Medicine, Tehran University of Medical Sciences, Tehran, Iran. 2019 01 06 Purpose: This study determines the effectiveness and/or necessity of applying postoperative  antibiotics in the treatment of mandible fractures. Materials and Methods: This is a randomized, double-blind clinical study using a placebo control. 65 patients diagnosed with mandibular fractures underwent open reduction and internal fixation surgery. The patients were randomly divided into 2 groups: antibiotic group (38 patients) and placebo group (27 patients), based on whether or not they received postoperative antibiotics. Both groups received preoperative as well as intraoperative antibiotics on the day of surgery. The antibiotic group was postoperatively given clindamycin 600 mg IV every 8 hours for 5-7 days. The placebo group received placebo using the same schedule for the same duration as the antibiotic group. Follow-up examination was performed at discharge, 2 and 3 weeks, postoperatively. Results: A total number of 65 patients participated in this study; 50 (76.9%) males and 15 (23.1%) females. The evidence of surgical site infection was noted in 24 out of 65 patients within 3 weeks post-operation totally, 13 out of 38 patients in the antibiotic group (34.3%) and 11 out of 27 patients in the placebo group (40.7%) had evidence of surgical site infections. No statistically significant difference in the incidence of infection was noted between the groups (p<.368). Conclusion: This study could not statistically prove any beneficial effect for post-operative administration of antibiotics in patients undergoing open reduction and internal fixation of mandibular fractures. https://jcr.tums.ac.ir/index.php/jcr/article/view/268 https://jcr.tums.ac.ir/index.php/jcr/article/download/268/242