1. Department of Prosthodontics and Biomaterials, Medical Faculty, RWTH Aachen University, Pauwelsstraße 30, 52074 Aachen, Germany
2. Department of Prosthetic Dentistry, Technische Universität Dresden, University Hospital Carl Gustav Carus, Dental School, Dresden, Germany
3. Department of Prosthetic Dentistry, Justus-Liebig University of Giessen, Gießen, Germany
4. Department of Prosthetic Dentistry, Christan-Albrechts University, Kiel, Germany
5. Department of Prosthodontics, Gerodontology and Biomaterials, Dental School, Ernst-Moritz-Arndt University of Greifswald, Greifswald, Germany
6. Ulm University, Center of Dentistry, Department of Prosthetic Dentistry, Albert-Einstein-Allee Ulm, Germany
7. Department of Prosthetic Dentistry, Julius-Maximilians University of Würzburg, Würzburg, Germany
8. Charité - Universitätsmedizin Berlin, CC3 – Charité, Center for Dental and Craniofacial Sciences, Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Campus Benjamin Franklin, Berlin, Germany
9. Department of Prosthetic Dentistry and Dental Material Science, University of Leipzig, Leipzig, Germany
10. Department of Prosthetic Dentistry, Albert-Ludwig University of Freiburg, Freiburg, Germany
11. University Medical Center Eppendorf, Department of Prosthodontics, Hamburg, Germany
12. Department of Prosthetic Dentistry and Dental Material Science, Friedrich-Schiller University of Jena, Jena, Germany
13. Department of Prosthetic Dentistry, Johannes-Gutenberg University of Mainz, Mainz, Germany
14. Department of Prosthetic Dentistry, Witten-Herdecke University, Witten, Germany
15. Department of Prosthodontics, Preclinical Education and Dental Materials Science, University of Bonn, Bonn, Germany
16. Danube Privat University Krems, Krems, Austria
17. Department of Prosthetic Dentistry, Ludwig-Maximilians University, Munich, Germany