Objective To discuss the etiology and prophylaxis measures of dry-socket.Methods A total of 4 897 cases of mandibular impacted third molar were randomly divided into two groups,2 284 cases in the group 1 were performed extraction by knocking chisel,while 2 613 cases in the group 2 were applied with extraction with turbine.The incidences of dry-socket were observed among these cases in both groups.Results The 87 cases of dry-socket were found in the group 1,and the incidence of dry-socket was 3.81%.No dry-so...