Root canal retreatment is a procedure used to clean the canals of a tooth that have already been subject to a root canal. Although most root canals are successful the first time, there are many reasons why a retreatment may be necessary. For example, some patients may have hidden canals that were not identified in the initial procedures, whereas others may experience a new infection caused by a loose crown or damaged filling. In some cases, these complications can occur immediately following a root canal when pain continues to persist and the tooth fails to heal. For other patients, complications can arise many years after an initial root canal. The goal of re-treatment is always the same as the initial root canal: Eliminate all bacteria from the inside of the tooth and seal it so that it is permanently protected from future infections.