1. Clinic of Fixed and Removable Prosthodontics and Dental Materials Science; University of Zurich; Zurich Switzerland
2. Sir John Walsh Research Institute; School of Dentistry; University of Otago; Dunedin New Zealand
3. Division of Biostatistics; Institute of Social and Preventive Medicine; University of Zurich; Zurich Switzerland
4. Clinic of Preventive Dentistry, Periodontology and Cariology; University of Zurich; Zurich Switzerland