Seong-Hun Kim1, Kyu-Rhim Chung2, Gerald Nelson3. 1. Department of Orthodontics, Graduate School, Kyung Hee University, Seoul, Korea. bravortho@gmail.com. 2. Department of Orthodontics, Graduate School, Kyung Hee University, Seoul, Korea. 3. Department of Orofacial Science, Division of Orthodontics, University of California, San Francisco.