The recurrence of pain after several years of root canal treatment is usually caused by incomplete root canal treatment, pulpitis, gingivitis, etc. Patients are advised to take appropriate treatment according to their own causes. 1. Incomplete root canal treatment: If the pain recurs due to incomplete root canal treatment, it is recommended to go to the hospital for pulp vitality test and other related tests, and if the tooth suffers from apical area lesions, the root canal filling should be removed under the guidance of the doctor and root canal exchange. 2. Pulpitis: If the patient suffers from tooth pain caused by pulpitis, he or she can be treated with root canal therapy by the doctor to relieve the pain. 3. Gingivitis: If the patient is suffering from gingivitis, you can under the guidance of the doctor through the scaling and other ways to alleviate the treatment, usually with hydrogen peroxide solution to clean the gum sulcus, can to a certain extent to remove the local irritating factors, so as to eliminate the inflammation. Patients are advised to pay attention to oral hygiene during the recovery process and to reduce the intake of sweets.