Tooth extraction is more painful than nerve killing. The extraction process will cause a lot of bleeding, and when extracting posterior teeth and obstructed wisdom teeth, due to the large number of roots and great resistance to root bifurcation, sometimes it is necessary to perform surgery such as cutting gums, separating soft tissues, splitting crowns, removing alveolar bone, etc. The large area of trauma will cause swelling in the jaw and face, and the pain will be severe after anesthesia, sometimes it is necessary to take oral painkillers, and the pain will be relieved only after 3-5 days. Nerve killing is performed under local block anesthesia and infiltration anesthesia, and the pulp has lost pain during the operation. Patients will have slight pain for 1-2 days after pulp removal, which will be relieved soon.