1. Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University at Kiel, Germany
2. Department of Prosthodontics, Gerodontology and Biomaterials, Greifswald University Hospital, Germany
3. Center for Clinical Studies, Christian-Albrechts University at Kiel, Germany
4. Medical Center – University of Freiburg, Center for Dental Medicine, Department of Prosthetic dentistry, Faculty of Medicine, University of Freiburg, Germany
5. Center of Dentistry, Department of Prosthetic Dentistry, Ulm University Hospital, Germany
6. Department of Prosthodontics, University Hospital Hannover, Germany
7. Department of Prosthetic Dentistry, Faculty of Medicine Carl Gustav Carus, TU Dresden, Germany
8. Center for Dental and Oral Medicine, Department of Prosthetic Dentistry, University Medical Center Hamburg-Eppendorf, Germany
9. Department of Prosthodontics, Heidelberg University Hospital, Germany
10. Department of Prosthodontics and Biomaterials, Medical Faculty, RWTH Aachen University, Germany