1. Department of Restorative, Pediatric and Preventive Dentistry, School of Dental Medicine, University of Bern, 3010 Bern, Switzerland
2. Department of Periodontology, School of Dental Medicine, University of Bern, 3010 Bern, Switzerland
3. Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, 3010 Bern, Switzerland
4. Division of Gerodontology and Removable Prosthodontics, University Clinics of Dental Medicine, University of Geneva, 1205 Geneva, Switzerland
5. Centre for Dentistry and Oral Health, University Medical Centre Groningen, 9713 AV Groningen, The Netherlands
6. Department of Surgery, Microsurgery and Medicine Sciences, School of Dentistry, University of Sassari, 07100 Sassari, Italy