1. Department of Prosthetic Dentistry, Propaedeutics and Dental Materials; University of Bonn; Bonn
2. Private Practice, Lennestadt; Germany
3. Institute for Medical Biometrics, Informatics and Epidemiology (IMBIE); Bonn; Germany
4. Division of Gerodontology and Removable Prosthodontics; University of Geneva; Geneva; Switzerland