1. Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, 14197 Berlin, Germany
2. Department of Prosthodontics and Material Science, University of Leipzig, 20251 Leipzig, Germany
3. Department of Prosthetic Dentistry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, 01069 Dresden, Germany
4. Department of Prosthodontics, Gerodontology and Dental Materials, Center of Oral Health, University Medicine Greifswald, 17489 Greifswald, Germany