Affiliation: | 1. Department of Community and Preventive Dentistry, School of Dentistry, University of Athens, P.O. Box 18018, Athens 11610, Greece;2. Department of Orthodontics and Dentofacial Orthopedics, Dental School, Medical Faculty, University of Bern, Bern, Switzerland;3. Department of Periodontology, School of Dentistry, University of Athens, Athens, Greece |