1. Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, 3010 Bern, Switzerland
2. Division of Gerodontology and Removable Prosthodontics, University of Geneva, 1205 Geneva, Switzerland
3. Department of Prosthodontics, Preclinical Education and Dental Materials Science, Medical Faculty, University of Bonn, 53113 Bonn, Germany