A root canal is made necessary when a cavity is allowed to reach all the way to the pulp. Sometimes deep dental restorations, or trauma to a tooth may cause the nerve to be damaged to the point it needs root canal therapy.

Once this occurs, the pulp becomes infected, and can even extend through the root tip and begin to infect the surrounding bone (this is 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. This infection is dangerous, and usually very painful. Symptoms that 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.

Sometimes, however, no symptoms are apparent, and the person is unaware of any problem until they come in for a dental exam.

Once the infection is resolved, the canal(s) are filled in to prevent any further infection. Usually a core build-up and crown is recommended for restoring a tooth that has had root canal therapy.