Root Canal Therapy is part of a branch of dentistry called endodontics. A tooth needs a root canal there is a significant amount of decay or if a tooth is fractured. A root canal is also needed when the nerve supply of a tooth is damaged and cannot repair itself. If this occurs and left untreated, the result could be an infection and pain and the possible loss of the tooth. Prior to endodontic therapy, the way to treat diseased teeth was to extract them. Now, root canals are performed to save teeth that once would have been extracted. After a root canal has been completed, it is vital to follow up with your dentist to be fitted for a crown to protect the tooth.