Old pain in the tooth after treatment mostly refers to the pain after root canal treatment. If the root canal treatment is successful, the pain usually disappears within 1 week, if the treatment is unsuccessful, the pain lasts for a longer period of time, or even persists or worsens. Root canal treatment is the most commonly used and effective treatment for endodontics and periapical diseases, using more instruments and complex steps, during and after the treatment, pain and other uncomfortable symptoms may occur, which is mostly a normal reaction, pay attention to the regular review can be, generally within 1 week the pain will disappear. If the root canal treatment is not successful, the toothache may persist or even worsen. If the pain is severe, accompanied by local swelling and systemic reactions such as fever, you should follow up with your doctor in time.