Root canal treatment or endodontics is the treatment of the root of a tooth that has become infected as a result of injury or decay. Usually a tooth that needs to be root treated causes pain and may be tender to pressure or have a swelling beside it on the gum (known as an abscess).  Sometimes the tooth darkens and is a sign that the nerve inside is dead and or infected. A local aneasthetic is usually given and so the treatment should not be painful.