Root canal treatment or endodontic therapy is used to save an infected or damaged tooth to avoid having it removed. A root canal becomes necessary when a neglected cavity reaches all the way to the pulp at the center of the tooth, causing the pulp to become infected.
Trauma can also cause deep damage to the nerve of a tooth. Once this occurs, the pulp becomes infected and begins to eat away at the surrounding bone (this is called an abscess). By the time the pulp is infected it must be treated and cannot heal on its own. It can even weaken the entire immune system, making it very dangerous and painful.
Symptoms of infected pulp may include severe sensitivity to hot/cold or sweets, pain, swelling, pain with biting or pressure, and a bad taste in the mouth. Sometimes, however, there are no symptoms, and you are unaware of any problem until a checkup.
A root canal is performed to clean out the infected tooth pulp and disinfect the canals of the tooth. The only other treatment would be to remove the tooth. Once the infection is resolved, the canal(s) is filled to prevent any further infection. Crowns are usually recommended to cover, reinforce and restore a tooth after root canal therapy.