1. Clinic of Fixed and Removable Prosthodontics and Dental Material Science; University of Zurich; Zurich; Switzerland
2. Implantology Department ACTA; Amsterdam; the Netherlands
3. Reconstructive Dentistry; Faculty of Odontology; University of Iceland; Reykjavík; Iceland
4. Institute of Social and Preventive Medicine; University of Berne; Berne; Switzerland