With the appropriate care, your teeth that have had endodontic treatment will last as long as other natural teeth. Yet, a tooth that has received treatment may fail to heal or pain may continue to exist. Sometimes, the pain may occur months or years after treatment. If so, Endodontic Retreatment may be needed. As occasionally happens with any dental or medical procedure, a tooth may not heal as expected after initial treatment for a variety of reasons: Narrow or curved canals were not treated during the initial procedure.