“When is it illegal for a licensed dentist in Arkansas to clean teeth? When he also happens to be a licensed orthodontist. In 2013, Dr. Ben Burris ran afoul of Arkansas’ law when he started offering low-cost teeth cleanings. Within weeks, Ben was told by the Arkansas State Board of Dental Examiners that he was breaking the law and that his license would be revoked if he continued offering the cleanings. Arkansas prohibits licensed dental specialists like orthodontists from doing work outside of their specialty even though they are qualified to practice general dentistry. Faced with the threat of seeing his practice ruined and his 100+ employees out of work, Ben suspended the program.”
http://fee.org/anythingpeaceful/detail/its-illegal-to-charge-too-little-for-teeth-cleaning