1. Department of Periodontology and Oral Implantology, Dental School, Faculty of Medicine and Health Sciences; Ghent University; Ghent Belgium
2. Oral Health Research Group (ORHE), Faculty of Medicine and Pharmacy; Vrije Universiteit Brussel; Brussels Belgium
3. Department of Oral Surgery and Stomatology, School of Dental Medicine; University of Bern; Bern Switzerland
4. Department of Prosthodontics, Faculty of Odontology; Malmö University; Malmö Sweden
5. Department Periodontology and Implantology; College of Dental Science, Radboud University Medical Center; Nijmegen The Netherlands