1. Department of Conservative Dentistry and Periodontology; Ludwig-Maximilians-Universität München; Munich Germany
2. Department of Preventive and Paediatric Dentistry; University Hospital of Jena; Jena Germany
3. Health Centre of Kyffhäuser District; Sondershausen Germany
4. Institute for Medical Informatics, Biometry and Epidemiology; Ludwig-Maximilians-Universität München; Munich Germany
5. Bioscience Research Center; The University of Tennessee Health Science Center; Memphis TN USA