After root canal treatment, the tooth has pressure pain, may be chronic apical periodontitis or periodontitis. 1. Chronic apical periodontitis: The success rate of root canal treatment is affected by anatomical factors, physician level and other factors, and there is a certain failure rate. If root canal treatment fails, the apical inflammation cannot be removed and pressure pain and bite discomfort will occur. It is recommended to re-treat the root canal. 2. Periodontitis: Root canal treatment is to treat diseases of the dental tissues, if the periodontal tissues of the teeth at the same time there is inflammation, there will be discomfort in biting and swelling of the gums and other symptoms, manifested as pressure and pain and swelling. Periodontal sequence treatment is needed. It is recommended to go to the regular hospital stomatology department, by the physician examination after a clear diagnosis, and the cause of the treatment.