The success rate of root canal treatment is at 95%. In extremely rare situations, a complication of the root canal may occur if the procedure is not correctly done. The following are the common indications: Persistent pain Mild discomfort is common to experience after the root canal. But, if the pain increases and persists following few days or if the tooth seems better at first, but spontaneous pain occurs, it may be an indication of failed root canal therapy. Swelling It is not uncommon for your face or mouth to swell for a day or two after the procedure. Your root canal may have failed if you experience any new swelling or if it persists. Charge If you notice bleeding or pus coming from the treated tooth or area around the gums, you may have an abscess. An abscess is usually accompanied by pain, but not always, so you should check any discharge for an abscess. Any invasive procedure may carry risks, and it is recommended to follow your dentist’s instructions or have a second opinion from a specialist.