A tooth that has had a root canal that has become pus-filled may generally be due to the presence of an inflammatory factor at the root tip, which can be treated by root refilling and oral medication. 1. Root refilling: If a fistula is formed locally after the failure of the first root canal treatment and the inflammatory infection reappears, there will be pus again after the root canal treatment of the tooth. At this time, the original filling needs to be cleaned out, and after the local inflammation subsides, the tooth root is filled again. 2. Oral medication: If the periodontitis patient after root canal treatment, bacteria into the periodontal pocket, the root of the tooth around the reoccurrence of infection, there may be the phenomenon of pus after root canal treatment, this time you need to rinse the periodontal pocket, root scraping, and then under the guidance of the doctor, the appropriate oral anti-anaerobic infections drugs, such as metronidazole tablets or tinidazole tablets and other drugs. Dental root canal treatment and then pus, it is recommended to the regular hospital stomatology, clear cause, symptomatic treatment.