1. Faculty of Medicine and Health Sciences; Department of Periodontology and Oral Implantology; Dental School; Ghent University; Ghent Belgium
2. Faculty of Odontology; Department of Prosthodontics; School of Dentistry; Malmö University; Malmö Sweden
3. Faculty of Dentistry; Department of Prosthodontics; School of Dentistry; University of Hong Kong; Hong Kong China