Root canal treatment is a procedure which is carried out to save the natural tooth and restoring its functional and esthetic purpose. Root canal treatment are generally painless, but due to some unwarranted reasons, root canal treated tooth can develop pain after years. The reasons for which are as below:-

  1. Missed Canals: Normal anatomy of anterior or posterior teeth can vary from patient. Sometimes, if the anatomy is complex or if there are more than one canals, there are high chances that the canals may be missed out. These missed canals add to the source of infection which leads to pain and may disturb the seal of the filled canals as well. This can cause failure of root canal therapy over the years.
  2. Secondary Caries: ill- fitting crowns may cause food lodgment which leads to secondary caries in a tooth. This in turn will gradually lead to pain in root canal treated tooth.
  3. Under filled canals: While obturating, certain canals are filled halfway not reaching the apex region. Such under filled canals lead to periapical lesions causing pain. Not necessarily, all under filled canals cause pain.
  4. Trauma from Occlusion: If the occlusion is imbalanced, it creates pressure on the root canal treated tooth leading to damage of periodontal ligaments over a period of time causing gradual pain.
  5. Poor oral hygiene: If the patient does not maintain proper oral hygiene, it may lead to food lodgment further causing gingivitis and periodontitis. An abscess can develop adjacent to the tooth or at the apex of the root leading to endo-perio lesion causing re-infection of the root canal treated tooth.
  6. Dislodged prosthesis leading to fracture of the tooth: If the patient fails to replace his or her broken prosthesis, it may lead to fracture of the tooth and dislodgement of the core build up done causing micro leakage and subsequent infection of the treated tooth.
  7. Other unknown causes.