1. Department of Conservative Dentistry and Periodontology, University Medical Center Regensburg, Regensburg, Germany;
2. Department of Preventive Dentistry, Academic Center for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands;
3. Department of Operative Dentistry and Periodontology, Faculty of Medicine, Center for Dental Medicine, University of Freiburg, Freiburg, Germany;
4. Department of Dermatology, University Medical Center Regensburg, Regensburg, Germany