In the American system of Dentistry, there are three levels:
- Board Certified Orthodontist
This is visually demonstrated by the ABO here.
Dentists have passed sufficient tests to qualify for ADA membership. This is about 160,000 members in the USA.
Orthodontists have passed sufficient tests to qualify for AAO membership, which includes about 19,000 members.
Once you have passed these tests, you can voluntarily study and take exams offered by the ABO, which need renewing every 10 years.
The ABO is recognized by both the ADA and AAO (in fact it is their only recognized orthodontic board). About 150 members became Board Certified, or renewed, in September 2017.
Just for reference, they have a Facebook page:
and provide a list of questions to ask your potential orthodontist: