Abstract: Abstract： Objective To evaluate effects of two different flap designs (envelope flap and triangular flap) on complica⁃ tions after the mandibular third molar surgery. Methods A randomized, self controlled clinical trial design was selected for 52 patients treated in the outpatient surgery of Stomatological Hospital Affiliated to Tianjin Medical University. Patients were treated with envelope flap design for lower third molar removal in one side and triangular flap on the other side. VAS scores were used to evaluate postoperative pain. The postoperative swelling was evaluated by patient` subjective index. The degree of the upper and lower incisor distance was used to evaluate trismus. Data of postoperative swelling, pain and trismus were re⁃ corded 1, 2 and 7 days after surgery. Data of postoperative wound dehiscence, bleeding situation and alveolitis were also re⁃ corded and compared between two groups. Results There were no significant differences in postoperative pain after 1, 2 and 7 days between two flap designs (P > 0.05). After 1 and 2 days there was more severe facial swelling in triangular flap group than that of envelope flap group (Z=2.005, Z=2.017, P < 0.05). There was more limited mouth opening after 1 and 2 days in triangular flap group than that of envelope flap group (t=2.578, t=2.410, P < 0.05), but on the seventh day there was no significant difference in the severity of facial swelling and trismus between two groups (P > 0.05). There were no signifi⁃ cant differences in postoperative pain, alveolitis, bleeding and wound dehiscence between two groups (P > 0.05). Conclu⁃ sion The envelope flap is more conductive to the early recovery in patients after surgery, but in the long term there is no ob⁃ vious difference between the two flap designs.

Key words: gingiva；molar, third；tooth extraction；postoperative complications；incision, envelope flap, triangular flap