Root canal therapy (RCT) is the most effective treatment for endodontic and periapical disease. Root canal therapy is performed to completely remove the source of infection in the root canal by debridement, chemical and mechanical preparation, and to tightly fill the root canal to prevent the occurrence of periapical lesions or to promote the healing of periapical lesions. Treatment steps 1. pulpal entry and crown preparation 2. root canal preparation: including cleaning and shaping of the root canal 3. Root canal disinfection: achieved by root canal irrigation and sealing. 4. Root canal filling: the cleaned, shaped and disinfected root canals are tightly filled and closed with biocompatible materials to create a favorable biological environment for the prevention and control of periapical histopathy. The advantages of root canal treatment are, first, that each step can be evaluated with objective indicators for quality control; second, that the root filling material used is biocompatible and does not cause harm to the human body, and that the root filling material can be removed when needed to facilitate root canal retreatment; and third, that the tooth after root canal treatment is conducive to pile crown restoration. The disadvantages of root canal treatment are that the operation steps are cumbersome (patients need to be seen several times and the treatment instruments are complicated), the technical requirements of the doctor are high, and the cost is relatively high.