1. Periodontology and Oral Implantology, Department of Oral Health Sciences, Faculty of Medicine and Health Sciences Ghent University Ghent Belgium
2. Department of Oral Health Sciences, Faculty of Medicine and Health Sciences Ghent University Ghent Belgium
3. Clinic for Removable Prosthodontics, Department of Oral Health Sciences, Faculty of Medicine and Health Sciences Ghent University Ghent Belgium
4. Department of Speech, Language and Hearing Sciences, Faculty of Medicine and Health Sciences Ghent University Ghent Belgium
5. Department of Communication University of Pretoria Pretoria South Africa
6. Department of Dentistry Radboud University Medical Center Nijmegen the Netherlands