A tooth has a canal(s) filled with pulp, containing blood vessels and nerve tissue. Sometimes, when decay progresses to the pulp of the tooth, infection and abscess may occur, requiring root canal therapy to salvage the tooth. Also, teeth with deep restorations may eventually require root canal therapy. Sometimes endodontic treatment is required when there has been trauma to the tooth, resulting in injury to the pulp that is not reversible. At this point, if root canal therapy is not done (and it is not always the best treatment option), then extraction of the tooth will be necessary to eliminate pain and infection.