1. Institute of Health Services Research in Dentistry University of Münster Münster Germany
2. Department of Restorative Dentistry, Periodontology, Endodontology, and Preventive and Pediatric Dentistry University Medicine Greifswald Greifswald Germany
3. Department of Epidemiology and Preventive Medicine University of Regensburg Regensburg Germany
4. Clinic for Periodontology and Conservative Dentistry University of Münster Münster Germany