Sealing pain after root canal treatment may be due to medicated periapical inflammation, missed root canals, apical inflammation and other reasons. 1. Pharmacological periapical inflammation: the root canal sealing drug is mainly a disinfectant and bactericidal effect, some drugs have too high a concentration of action or the existence of semi-antigenic, such as formaldehyde cresol, it is easy to form a pharmacological apical periapical inflammation. Manifested as swelling and pain, serious facial swelling, the need to remove the drug, replace the drug. 2. Missing the root canal: the root canal system is complex, for some anatomical variations of the root canal, it is easy to miss, resulting in the sealing of the root canal, hidden pain after closure. It is necessary to find the root canal and continue root canal preparation. 3. Root tip inflammation: when dredging some calcified root canals or operating too violently, it is easy to cause stimulation to the root tip, causing pain after sealing, and it is recommended to remove the temporary sealing and anti-inflammatory treatment. Root canal system is complex, part of the treatment is difficult, it is recommended to go to the regular hospital stomatology department.