1. aAssistant Professor, Department of Orthodontics and Dentofacial Orthopedics, Center of Dentistry, Georg-August-University, Goettingen, Germany
2. bConsultant, Zürich, Switzerland
3. cResearch Assistant, Clinic for Preventive Dentistry, Periodontology and Cariology, University of Zürich, Zürich, Switzerland
4. dProfessor and Head, Clinic for Preventive Dentistry, Periodontology and Cariology, University of Zürich, Zürich, Switzerland