The pain of sealing the tooth after root canal may be caused by the irritation reaction of the drug, or infected with inflammation, root canal residue and other factors, which need to be treated according to the cause of the disease, as follows. 1. Irritation reaction of medication: after sealing the root canal of the tooth, it may produce irritation reaction in the short term, which is a normal performance, and can be observed temporarily without special treatment. 2. Inflammatory infections: if the root canal sealing drug is not properly localized care, resulting in inflammation invasion, easy to cause inflammatory reactions, need to follow the doctor’s instructions oral metronidazole or tinidazole anti-inflammatory. 3. Root canal residue: the residual tissue is not cleaned up before root canal treatment, which may cause toothache after sealing. A follow-up appointment is needed to clean up the residual tissue and reseal the medication. Regarding the symptoms of tooth pain after root canal sealing, the cause of the disease should be clarified first, and then carry out regular treatment. During this period, oral hygiene should be observed to minimize secondary infections, and any discomfort should be treated promptly.