1. Department of Preventive Dentistry, Shanghai Key Laboratory of Stomatology, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, P.R. China
2. Department of Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong, SAR, P.R. China
3. Department of Orthodontics, Shanghai Key Laboratory of Stomatology, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, P.R. China