Root canal treatment, commonly known as nerve killing, is the main means of treating dental and endodontic diseases and periapical diseases, patients usually need to visit the clinic 1-3 times, the specific treatment methods are as follows: 1, 1-time root canal treatment: mainly for accidental pulp exposure due to tooth trauma or infection only in the root canal, under adequate conditions, local anesthesia after pulp removal, root canal preparation and molding, rinsing and cleaning immediately after root canal 2.2 times method of root canal treatment: the first time to remove the pulp under local anesthesia, root canal cleaning and shaping, rinsing and sealing with sterilization and disinfection drugs, and root canal filling after an interval of 7 days; 3.3 times method of filling: mainly for acute periapical infection and pulpitis in which the pulp cannot be removed cleanly. The pulp is opened and drained under local anesthesia for the first time, and 2 visits are made after an interval of 3-5 days to remove the pulp, prepare the root canal, clean and shape it, and seal it with sterilizing and disinfecting drugs. Root canal filling can be performed on the 3rd visit without subjective symptoms. After root canal filling, the tooth is prone to become fragile and fracture. It is recommended that the patient undergo crown restoration after 1 week of treatment and observation to prevent the tooth from splitting due to unexpected circumstances.