If the tooth decay is deep and the pulp has been damaged, root canal treatment is needed. The whole process of root canal treatment can be roughly divided into 4 steps: 1.open pulp and drainage, under local anesthesia, open pulp and drainage, remove the infected nerve in the root canal. 2.prepare root canal, through special root canal preparation instruments, root canal files, etc., remove the decayed tissue in the root canal and form a specific channel, which can facilitate the next step of root canal filling. 3.root canal disinfection, after root canal preparation, root canal disinfection medicine should be placed in the root canal. After all the infected bacteria in the root canal are completely eliminated, the last step is to carry out root canal filling, using special root canal filling material, the canal channel is completely closed to avoid subsequent bacterial re-invasion and infection, which is the whole process of root canal treatment.