1. Department of Operative Dentistry, Periodontology and Preventive Dentistry, Rheinisch-Westfälische Technische Hochschule University Hospital, Pauwelsstrasse 30, 52074 Aachen, Germany
2. Department of Operative Dentistry, Endodontics and Pediatric Dentistry, Campus Marburg, University Medical Center Giessen and Marburg, Georg-Voigt-Strasse 3, 35039 Marburg, Germany
3. Center for Oro-Dental Microbiology, Hamburger Chausse 25, 24220 Flintbek, Germany