1. Graduate student, Graduate School of Clinical Dentistry, Ewha Womans University, Seoul, Korea
2. Assistant Professor, Division of Orthodontics, Department of Dentistry, Ewha Womans University, Seoul, Korea
3. Assistant Professor, Department of Orthodontics, School of Dentistry & Dental Research Institute, Seoul National University, Seoul, Korea
4. Professor, Division of Orthodontics, Department of Dentistry, Ewha Womans University, Seoul, Korea
5. Corresponding author: Dr Youn Sic Chun, Division of Orthodontics, Department of Dentistry, Ewha Womans University, Seoul, Korea. 911-1 Mokdong, Yangcheon-gu, Seoul 158-710 Korea (yschun@ewha.ac.kr)