Objective To research the reaction of rat, mandibular bone in histology in different periods after being hurt by air turbine handpiece,chisel and surgical turbine in different ways and to know the different degree of hurt in those methods, to find a safe way in bone removal for clinic.

Objective To compare the effects of high-speed air-turbine drill and traditional chisel technique in removal of impacted mandibular third molars,and to evaluate the superiority of the high-speed air-turbine drill.