Occasionally a tooth that has undergone endodontic treatment fails to heal or pain continues despite therapy. Although rare, sometimes a tooth initially responds to root canal therapy but becomes painful or diseased months or years later. When either of these situations occur, the tooth often can be maintained with a second endodontic treatment. This is known as a retreatment and can be accomplished in a non-surgically manner. Occasionally a surgical option known as an apicoectomy will be recommended.