Background: Odontectomy is one of the most common surgical procedures in oral and maxillofacial surgery. Flap design influences the post operative complications. Triangular flap is the most widely used flap design but it has many shortages such as dehiscence, alveolar osteitis, reactionary bleeding, and periodontal disruption distal of second molar. The aim of this study is to introduce an alternative flap design in the surgical removal of impacted mandibular third molars ? reversed triangular flap ? and to compare this flap design with the triangular flap in case of dehiscence, reactionary bleeding, and clinical attachment loss. Material and Methods: This prospective, split-mouth study involved 15 patients with bilateral partially impacted mandibular third molars with similar impaction classification. One impacted tooth was removed using a triangular flap and the other using a reversed triangular flap. Post operative complications such as dehiscence, reactionary bleeding, and clinical attachment loss were recorded 1, 3, 7, 14, and 30 days post odontectomy. Results: Chi square test result shows that there were fewer incidences of dehiscence seven days post surgery using the reversed triangular flap (p=0.032). Mann Whitney-U test result shows that the reversed triangular flap exhibited less bleeding score on day 1 (p=0.002) and day 2 (p=0.035) post surgery. There were no statistically significant differences according to Mann Whitney-U test between the flap designs for the clinical attachment loss on distal of second molar on day 14 (p=0.512) and day 30 (p=0.902) post surgery. Conclusions: The reversed triangular flap design is preferable to triangular flap for impacted third molar surgery, escpecially in terms of wound dehisence and reactionary bleeding.