The success rate of a first root canal treatment, if performed conscientiously, is very high. However, for various reasons, it may sometimes fail and have to be repeated.

Endodontic re-treatment is only possible under certain conditions, especially if the tooth does not have a fracture or is not affected by a deep cavity. If this is the case, apectomy or extraction may be considered.

Different problems and/or complications can sometimes occur after a first root canal treatment, and require its resumption:

• The formation of a new cavity on the treated tooth;
• An infection, due to the proliferation of intraradicular bacteria;
• The infected ducts were not sufficiently cleaned or some very narrow, difficult to access or invisible channels due to inflammation could not be disinfected during the first root canal treatment;
• The initial sealing was not waterproof enough.

Some symptoms may be indicative of these complications, including:

• Severe pain lasting several days or even weeks;
• Sensitivity to temperature changes (hot and cold) lasting beyond a few weeks;
• A sensitivity to pressure lasting beyond a few weeks;
• Swelling in the gums and redness;
• The presence of suppuration (pus discharge) in the gums.

• The possibility of reworking the root canal allows the natural tooth to be preserved;
• Sensitivity and pain are eliminated;
• More serious complications, including a periapical abscess or an infection that can spread to the rest of the body, are prevented;
• The success rate of a root canal resumption remains high.

• A resumption of root canal treatment cannot be performed on a tooth that is fractured or affected by deep caries.

If the treated tooth shows signs of infection and is not reprocessed, some more serious complications may occur, including :

• the loss of the tooth;
• a periapical abscess;
• a sinus infection;
• sepsis (a discharge of bacteria into the blood that can lead to fatal consequences).

There are several aspects to consider when evaluating the cost of resuming root canal therapy:

• First, the cost of treatment depends on the number of channels the tooth has (from 1 to 4);
• Second, the cost of root canal treatment at a general dentist includes the following procedures, spread over one or more appointments: the treatment plan, clinical procedures (cleaning, shaping of the canals and root canal filling) and x-rays;
• Finally, the cost of root canal treatment excludes the final restoration of the tooth. It will therefore be necessary to add the cost of an amalgam or composite restoration. A crown can also be suggested. In this case, additional costs may be added, especially if a pivot is required for the installation of the crown.

In all cases, the fees are based on the Association des chirurgiens dentistes du Québec (ACDQ) Guide des tarifs et nomenclature des actes buccodentaires.

• Tooth with a fracture;
• Deep cavity;
• Poor prognosis of the tooth.

In these specific cases, tooth extraction is recommended.

• The dentist first examines the condition of the tooth in question to determine if root canal reprocessing is the most appropriate procedure. The condition of the gums and periodontium, the tissues that support the tooth, is also assessed;
• If resuming root canal therapy is identified as the best solution, the dentist will first perform local anesthesia;
• A dam is then placed around the tooth to prevent contamination and the filling is removed to allow access to the tooth channels;
• Canals that have not been treated during the first root canal treatment and/or those that have not been sufficiently cleaned are disinfected with an antibacterial solution. The dentist may use a microscope to detect additional channels that are difficult to see with the naked eye;
• The tooth is filled again with a plastic material and a temporary dressing is applied;
• A second appointment is often required to make the final restoration of the tooth, usually with a CEREC crown or laboratory crown.

• In order to ensure the longevity of the treated tooth, and the success of the treatment, it is essential to follow the recommendations made by your dentist after the procedure;
• Oral hygiene measures, including brushing teeth 2 to 3 times a day, flossing and using interdental brushes if necessary, should be strictly applied to reduce the risk of complications;
• Consult your dentist once or twice a year, or as recommended by your dentist, for cleaning (prophylaxis) and routine examination.

• Apectomy;
• Extraction.