Occasionally with any dental or medical treatment the tooth does not heal as expected. Reasons for retreatment are delay in restoring treated tooth, untreated canal, new or recurrant decay or tooth fracture. Often a revision of previous treatment can save the tooth. The tooth is accessed again and the old root canal fillings is removed.. Then with the use of the microscope and fiber optics the tooth is carefully examined inside to possibly locate an untreated canal. When retreatment is completed you will again be advised to return to your dentist for the necessary restorative procedure.