1. Clinic for Conservative Dentistry and Periodontology, School for Dental Medicine, Christian-Albrechts-Universität zu Kiel, Arnold-Heller-Str. 3, Haus 26, 24105 Kiel, Germany
2. Department of Medical Informatics, Biometry, and Epidemiology, Charité Centrum 4, Institute of Medical Biometry and Clinical Epidemiology, Charité-Universitätsmedizin Berlin, Hindenburgdamm 30, 12203 Berlin, Germany