The American Association of Orthoontists, or AAO, is an American advocate group for orthodontists. Most American orthodontists, about 95 percent, are members. They are also dentists and are members of the American Dental Association. Orthodontists are specialists in the diagnosis, prevention and treatment of orthodontic problems. After dental school, orthodontists are required to successfully complete a minimum of two academic years of study in an accredited orthodontic residency program. Only those who have completed this training may call themselves "orthodontists," and only orthodontists may be members of the American Association of Orthodontists.