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