1. Department of Periodontology & Oral Implantology; Faculty of Medicine and Health Sciences, School of Dental Medicine; Ghent University; Ghent Belgium
2. Center for Periodontology and Implantology Leuven; Heverlee Belgium
3. Vrij Universiteit Brussel (VUB); Brussels Belgium
4. Department of Biomedical Statistics; Ghent University; Ghent Belgium
5. Department of Prosthodontics; University of Malmö; Malmö Sweden