1. a Associate Professor, Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, 100081 China
2. b Thomas M. and Doris Graber Endowed Professor of Dentistry, Department of Orthodontics and Pediatric Dentistry, School of Dentistry; Professor of Cell and Developmental Biology, School of Medicine; and Research Professor, Center for Human Growth and Development, The University of Michigan, Ann Arbor, Mich. Private practice of orthodontics, Ann Arbor, Mich