1. Department of Orthodontics, College of Dentistry, Yonsei University, Seoul, Korea.
2. Department of Orthodontics, College of Dentistry and Institute of Craniofacial Deformity, Yonsei University, Seoul, Korea.
3. Research Institute of Dental Biomaterials and Bioengineering, BK21 Project, College of Dentistry, Yonsei University, Seoul, Korea.