Root canal treatment, the second release of medicine, very painful, may be missed root canals, medicated periapical inflammation, postoperative reaction, etc., need to redo the root canal preparation or oral amoxicillin capsules, clindamycin capsules, cefprozil and other drugs to relieve. Root canal treatment is mainly divided into root canal preparation, root canal disinfection and root canal filling three major steps, the second release of pain may be the following situations. 1. Missing root canals: Some complex root canal systems often have variations, which can lead to missing root canals during root canal preparation and pain after closure. It is necessary to search for the missing root canal for preparation and disinfection. 2. Drug-induced periapical inflammation: The improper use of some medications for root canal disinfection, such as excessive dosage of medication or body allergies, may easily lead to drug-induced periapical inflammation, with obvious pain and facial swelling in severe cases. Need to remove the drug after anti-inflammatory treatment, such as oral amoxicillin capsules, metronidazole tablets, clindamycin capsules and so on. 3. Postoperative reaction: some teeth root canal treatment process will push out the material in the root canal out of the apical foramen, resulting in postoperative swelling and pain. It is recommended to observe, if the pain is obvious, you can take oral cephalosporins anti-inflammatory treatment, such as cefprozil, cefaclor and so on. It is recommended that patients with post-treatment pain should consult a doctor in time to avoid unnecessary pain. Drugs should be used under the guidance of a physician.