Root canal treatment (also called root canal therapy or endodontic therapy) is necessary when an untreated cavity reaches the pulp. Treatment may also be needed when deep restorations or trauma to a tooth causes nerve damage. Once the pulp becomes infected, and can begin to eat away at the surrounding bone (this is known as an abscess). If the pulp is infected, it is painful and will require treatment as it cannot heal on its own. Symptoms that indicate the pulp has become infected may include sensitivity to hot/cold or sweets, pain, swelling, pain to biting or pressure, and a bad taste in the mouth. However, sometimes no symptoms are apparent, and you may be unaware of any problem until a checkup.
A root canal cleans out the infected tooth pulp and disinfects the tooth canals. An alternate treatment would be to extract the tooth. Once the infection is resolved, the canal is filled to prevent further disease. Usually, a core build-up and crown are recommended for restoring a tooth that has undergone root canal therapy.