A root canal is a procedure used to save a tooth that has had an infection that has reached the nerve. Although normal tooth decay can become increasingly worse and eventually lead to a root canal, often trauma can cause the tooth to die as well. In a root canal, the dentist removes the dead nerve from the tooth, cleans the tooth out on the inside, and seals it off to prevent another infection or abscess from forming around the tooth. If the nerve and all the infection is not removed the bacterial continues to move deeper down the root and into the bone, often causing swelling, pain, and discomfort that worsens with time.