Pain: Pain is the most common symptom of needing a root canal. The pain that comes from a tooth needing a root canal is fairly specific. If the tooth is still alive, it will become extremely sensitive to hot or cold, and will remain sensitive even after the hot or cold stimulus is taken away from the tooth. The tooth may start to hurt spontaneously, in the middle of the night, or sometime when the patient isn't even using the affected tooth to eat or drink. If the tooth is dead and has become abscessed, the patient will feel pain when he or she chews or puts pressure on the tooth.

Abscess: If a tooth has become abscessed, it will require a root canal. An abscess forms when the pulp of the tooth dies and a pus pocket forms around the end of the root. The pus accumulates in an area of dead nerve tissue that is infected with bacteria. Sometimes the abscess will form a bump that looks like a pimple on the outside of the gums. A patient may even notice pus draining from the pimple or notice a bad taste in his or her mouth.

An abscess that is left untreated will continue to grow and infect the bone around the root of the tooth. It may spread into surrounding bone and tissues. In rare cases, people have died from infections that started from a tooth abscess. Although antibiotics can help keep the infection from spreading, the only way to remove the infection completely is by performing root canal treatment and cleaning out all the dead tissue and bacteria inside the pulp chamber and root canals.

Deep cavity: If tooth decay extends deep into the tooth and reaches the pulp, the pulp will become infected with bacteria. When this happens, it will either become inflamed and painful, or it will die and become decayed tissue. Sometimes there will be no pain, but the only way the dentist can get all of the tooth decay out of the tooth is by performing a root canal and removing the nerve that has become affected as well.

Trauma: If a tooth is hit with great force, the nerve can be severed at the end of the root and eventually die. This could happen immediately after the traumatic incident, or it may happen over many years following the trauma.

Fracture: A tooth that has become fractured may need a root canal if the fracture extends deep into the tooth and reaches the pulp. If a tooth has fractured in a way that doesn't leave very much tooth structure left above the gum line for a crown or other restoration, a root canal may need to be performed so a post and can be placed down the canal of the tooth to help retain the restoration.

Repeated dental procedures: Dental procedures produce a lot of stress on a tooth. Sometimes repeated drilling may cause the pulp of a tooth to become inflamed. The tooth will need to be tested by a dentist to determine whether the inflammation is reversible or irreversible.

In the past, whenever one of these situations happened to a tooth, the only treatment option was to have it extracted. Root canal treatment is an extremely beneficial option that allows for most teeth to be saved in the mouth and used effectively for a very long time. Once the teeth are formed, they don't need the pulp to function properly. The pulp provides the tooth sensation to a stimulus like hot or cold, but it isn't required for the tooth to remain functional in a healthy mouth.