1. Radboud University Nijmegen Medical Centre, College of Dental Sciences, Preventive and Restorative Dentistry, Ph van Leydenlaan 25, PO Box 9101 6500HB Nijmegen, The Netherlands
2. Federal University of Pelotas, Graduate Program in Dentistry, Gonçalves Chaves, 457, 5th floor, Pelotas, RS, 96015560, Brazil
3. Vrije Universiteit Brussels, Dept. of Oral Health Sciences, Laarbeeklaan 103, BE 1090 Brussels, Belgium
4. Faculty of Health and Medical Sciences, University of Copenhagen, Institute of Odontology, Nørre Allé 20, DK-2200, Copenhagen, Denmark
5. Universität Witten/Herdecke, Abteilung für Zahnerhaltung und Präventive Zahnmedizin, Alfred-Herrhausen-Str. 44, D-58455 Witten, Germany
6. Umeå University, Department of Odontology, SE-901 85 Umeå, Sweden