When a severe toothache occurs, a tooth may require root canal treatment (endodontics) in order to save it. Accidental injury or deep decay can damage the nerve inside the root of a tooth, causing inflammation or infection. Early signs of infected nerve tissue include toothache, infection around the gum of the tooth, or swelling of the face. The procedure involves the removal of the infected tissue inside the tooth and the cleansing and sealing of the canal which housed it. Following root canal treatment, the tooth is best restored with a crown in order to prevent further damage and extend its life. In some instances, a tooth that is very badly damaged from decay or injury may be unrestorable or unsuitable for root canal treatment and requires extraction.