1. Department of Orthodontics, Postgraduate Dental Education Center , Örebro , Sweden
2. School of Medical Sciences, Faculty of Medicine and Health, Örebro University , Örebro , Sweden
3. Private orthodontic office , Traben-Trarbach , Germany
4. Private orthodontic office , Moscow , Russia
5. Clinical Epidemiology and Biostatistics, School of Medical Sciences, Faculty of Medicine and Health, Örebro University , Orebro , Sweden
6. Department of Orthodontics, University of Saarland , Homburg/Saar , Germany