Also referred to as endodontic therapy, root canals are necessary when a cavity goes all the way to the pulp (nerves and vessels) of the tooth. Root canals are often necessary to prevent extraction of the tooth. Sometimes trauma or deep restorations may cause a nerve to be damaged to the point that a root canal is needed. When the pulp becomes infected, it can extend through the tip of the root and affect the surrounding bone which is an abscess. Symptoms that the pulp has become infected and a root canal may be needed may include sensitivity to hot/cold or sweets, pain, swelling, pain to biting or pressure and even a bad taste in the mouth.