1. Department of Periodontology, Operative and Preventive Dentistry, University of Bonn, Welschnonnenstrasse 17, 53111 Bonn, Germany
2. Independent Researcher, Lortzingstraße 38, 53332 Bornheim, Germany
3. Department of Paediatric Dentistry, University Clinic of Dentistry, Medical University of Vienna, Sensengasse 2a, 1090 Vienna, Austria
4. Independent Researcher, Glogauer Straße 28, 53117 Bonn, Germany