1. Institute for Medical Epidemiology, Biometrics and Informatics (IMEBI), Interdisciplinary Centre for Health Sciences, Medical School of the Martin Luther University Halle-Wittenberg , Magdeburgerstraße 8 , 06112 Halle (Saale), Germany
2. Department of Operative Dentistry and Periodontology, School of Dental Medicine, Martin Luther University Halle-Wittenberg , Halle, Germany
3. Department of Public Health, Child and Youth Medical Service , Saalekreis, Germany