A root canal is a procedure used to repair and save a tooth that is badly decayed or becomes infected. Although decay is the most common cause of needing a root canal, sometimes blunt trauma can cause the tooth to die. Your dentist will remove the dead nerve from the tooth and then seal it off to prevent another infection or abscess from forming around the tooth. If the nerve is not removed the infection will continue to climb deeper into your gums, often causing swelling, pain, and discomfort.