1. Faculty of Medicine and Health Sciences, School of Dental Medicine, Department of Periodontology and Oral Implantology Ghent University Ghent Belgium
2. Center for Periodontology and Implantology Leuven Heverlee Belgium
3. Biostatistics Unit, Faculty of Medicine and Health Sciences Ghent University Ghent Belgium
4. Radbound University Medical Center Implantology and Periodontology Nijmegen The Netherlands
5. Department of Prosthodontics University of Malmö Malmö Sweden
6. Private Practice Periodontology and Oral Implantology Geluwe Belgium