A registered dental hygienist (RDH) is a licensed dental professional who specialises in preventive oral health, typically focusing on techniques in oral hygiene. Dental hygienists provide three types of services to their patients. The first of these is preventive services to promote and maintain good oral health. The second is educational services to help patients develop behaviours that promote better oral heath and help them understand the importance of practicing these behaviours. The third type of service provided is therapeutic services which are treatments meant to stop disease and maintain healthy tissues in the mouth.