| A root canal can fail for several reasons. If your dentist failed to remove all of the infection from a canal or did not clean out all of the canals, the tooth can become infected again. Or, if there is leakage around an old filling or crown, bacteria can get in and reinfect a root canal. Although the procedure itself is the same, a repeat root canal treatment tends to be more involved and time consuming than the original one because your dentist must remove the restorative material before he or she can do the second root canal. That's why retreatment generally costs more than the first root canal. Another reason that a retreatment may take longer is that failed root canal treatments often involve infections that are difficult to destroy. Some people may also need endodontic surgery, either instead of or after retreatment. Endodontic surgery is done instead of retreatment if performing a second root canal is problematic. For example, if the tooth that has had root canal treatment has a post-and-core restoration, it may be difficult to remove the restoration without injuring the tooth. If the tooth still is infected after retreatment, endodontic surgery may be called for. During endodontic surgery, your endodontist makes a small incision in the gum near the tooth and cleans out the infected tissue around the tip (apex) of the root. He or she then shaves off 3 to 4 millimeters of the root (a procedure called an apicoectomy), cleans the inside of the canal from the root end, and places a filling in the end of the root. The incision is then stitched. The success rate for this surgery is 80% to 90%. If the surgery is not successful in removing the infection, the tooth will have to be extracted. ©2002-2005 Aetna, Inc. All rights reserved. Reviewed by the faculty of Columbia University College of Dental Medicine | 
