1. Faculty in Orthodontics, Department of Preventive Dental Sciences, College of Dentistry, King Faisal University, Al Ahsa 31982, Saudi Arabia
2. Department of Preventive Dental Sciences, College of Dentistry, King Faisal University, Al Ahsa 31982, Saudi Arabia
3. Community Dental Services, Port Talbot Research Centre, Swansea Bay University Health Board, Port Talbot SA12 7BJ, UK