Although initial root canal treatment was successfully completed, the tooth may sometimes fail to heal. The tooth may become painful or diseased months or even years after successful treatment due to various reasons:

• Narrow or curved or calcified canals that were untreated during the initial procedure
• Complicated canal anatomy went undetected in the first procedure
• The crown or other restoration was not placed soon enough after the procedure causing recontamination of the canal system
• The restoration did not prevent saliva from contaminating the inside of the tooth
• New decay can expose the root canal filling material to bacteria, causing a new infection in the tooth.
• A loose, cracked or broken crown or filling can expose the tooth to new infection.

When this happens the endodontist can try to save the tooth by retreating the canal system. It involves removing the existing canal filling, exploring for new or untreated canals. This is usually done using an operating microscope, ultrasonic and digital imaging and will involve more time and effort in doing the procedure. The canals are then sealed with the canal filling. Sometimes retreatments are done in conjunction with endodontic surgery. Your endodontist will discuss your options and recommend appropriate treatment.