1. Department of Operative and Preventive Dentistry, Faculty of Health, School of Dentistry, Witten/Herdecke University, Witten, Germany
2. Department of Periodontology, Faculty of Health, School of Dentistry, Witten/Herdecke University, Witten, Germany
3. Institute of Medical Biometry and Epidemiology, Faculty of Health, School of Medicine, Witten/Herdecke University, Witten, Germany
4. Department of Oral Surgery, Faculty of Health, School of Dentistry, Witten/Herdecke University, Witten, Germany