1. Heidelberg University, Section of Periodontology, Department of Conservative Dentistry, Clinic for Oral, Dental and Maxillofacial Diseases, University Hospital Heidelberg, Heidelberg, Germany
2. Department of Orthodontics and Dentofacial Orthopaedics, Dental School, Heidelberg University, Heidelberg, Germany
3. Institute of Medical Biometry, University of Heidelberg, Heidelberg, Germany
4. Department of Orthodontics, University Hospital Schleswig-Holstein, Kiel, Germany