Prosthodontics, also known as dental prosthetics or prosthetic dentistry, is the area of dentistry that focuses on dental prostheses. It is one of 12 dental specialties recognized by the American Dental Association (ADA), Royal College of Surgeons of England, Royal College of Surgeons of Edinburgh, Royal College of Surgeons of Ireland, Royal College of Surgeons of Glasgow, Royal College of Dentists of Canada, and Royal Australasian College of Dental Surgeons. The ADA defines it as "the dental specialty pertaining to the diagnosis, treatment planning, rehabilitation and maintenance of the oral function, comfort, appearance and health of patients with clinical conditions associated with missing or deficient teeth or oral and maxillofacial tissues using biocompatible substitutes. According to the ADA, specialties are recognized in those areas where advanced knowledge and skills are essential to maintain or restore oral health (Principles of Ethics and Code of Professional Conduct). Not all areas in dentistry will satisfy the requirements for specialty recognition. Acknowledged by the profession, the contributions of such and their endeavors are encouraged. Treatment is multidisciplinary, involving oral and maxillofacial surgeons, plastic surgeons, head and neck surgeons, ENT doctors, medical oncologists, radiation oncologists, hospital dentists, speech pathologies (speech therapists), clinical psychologist, occupational therapists, physiotherapists, and other healthcare professionals.