1. Department of Orthodontics, University of Giessen, Giessen, Germany
2. Private Practice, Mainz, Germany
3. Department of Medical Statistics, University of Giessen, Giessen, Germany
4. Orthodontics, Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland
5. Orthodontics, Oral and Maxillofacial Diseases, Helsinki University Hospital and University of Helsinki, Helsinki, Finland