Endodontics (from the Greek endo "inside"; and odons "tooth") is the dental specialty concerned with the study and treatment of the dental pulp. Endodontists perform a variety of procedures including endodontic therapy (commonly known as "root canal therapy"), endodontic retreatment, surgery, treating cracked teeth, and treating dental trauma. Root canal therapy is one of the most common procedures. If the dental pulp (containing nerves, arterioles, venules, lymphatic tissue, and fibrous tissue) becomes diseased or injured, endodontic treatment is required to save the tooth. Endodontics is recognized as a specialty by many national dental organizations including the American Dental Association, Royal College of Dentists of Canada, and Royal Australasian College of Dental Surgeons.