Objective To study the effect of piezosurgery in the extraction of mandibular impacted third molars. Methods 228 mandibular impacted third molars with relative difficulty for extraction according to the scheme of degree of difficulty for extraction were included in the study, and were divided into two groups（114 teeth each group）: Test group（treated by piezosurgery）, control group（treated by traditional chisel osteotomy）. The surgery time and pain. restriction of mouth opening and facial swelling after surgery, were evaluated in both groups. Results The average surgery time was （16±5.2）min in test group and （30±8.7）min in control group. The surgery time, pain, facial swelling rate, and restriction of mouth opening were lower than control group（P
