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Although root canal treatment is highly successful, a root canal can fail for several reasons. They include:

  • Incomplete removal of the bacteria from the canals
  • Waiting too long after the root canal to get a permanent restoration (crown or filling.) In this case the bacteria can reinfect the root canal.
  • Not all the canals were located during treatment. The bacteria in the untreated canal can cause pain and infection.
  • The tip of the root was not properly sealed during treatment
  • Root fracture
  • Separated instruments in a canal, during the procedure

A repeat root canal treatment tends to be more involved and take more time than the first one, so it also is more costly. Your dentist must remove the crown, post and core, and filling material before doing the second root canal. Some people who need another treatment may have infections that are difficult to control.

Sometimes a second root canal can be hard to do. For example, it may be too risky to remove a post and core. The post that is in the tooth may be cemented or set in very tightly. If that is the case, the tooth may be fractured in the process. Your dentist may therefore decide to do endodontic surgery instead. This surgery allows the dentist to get inside a tooth's root from the bottom of the tooth, rather than from the top (the crown).

Endodontic surgery is done in the dentist's office. An endodontist, general dentist or oral surgeon can perform this procedure. First, you will receive a shot to numb the area. Then your dentist will make a small cut (incision) in the gum near the base of the tooth. He or she will clean out the infected tissue around the tip (apex) of the root and shave off the tip. This procedure is called an apicoectomy. The endodontist will clean the inside of the canal from the root end, and then put a filling in the end of the root. The incision is then stitched.

Endodontic surgery is successful about 85% of the time. It is typically done only on premolars and front teeth. It is sometimes done on molars, although with a lower success rate. If the surgery does not get rid of the infection, the tooth will have to be extracted. Factors complicating surgical treatment include severe curvature of the roots and the internal root canal system.


Last updated May 7, 2021



  • Signor B,Blomberg L, et al. Root canal retreatment:A retrospective investigation using regression and data mining methods for prediction of technical quality and periapical healing. J Appl Oral Sci.2021;29:e20200799. Doi:10.1590/1678-7857-2020-0799. PMID:33886941
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