The Second Time Around: Possible Retreatment or Surgery
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.