Jie Zhen1, Cong-Hua Liu2, Wen-Xuan Zhang3, Li-Shu Zhou4, Hao-Xian He4, Xuan Qin5, Ze-Dong Lan6. 1. Postgraduate student, Orthodontic Program, Department of Stomatology, Shenzhen Hospital of Guangzhou University of Chinese Medicine, 6001 Beihuan Blvd., Shenzhen, China K1H 8L1; e-mail: janejie3@foxmail.com. 2. Professor and Chief, Department of Orthodontics, Stomatological Hospital of Southern Medical University (Guangdong Provincial Stomatological Hospital), Guangzhou, China. 3. Postgraduate student, Oral Surgery Program, Third Hospital of Hebei Medical University, Shijiazhuang, China. 4. Postgraduate student, Department of Orthodontics, Stomatological Hospital of Southern Medical University (Guangdong Provincial Stomatological Hospital), Guangzhou, China. 5. Postgraduate student, Orthodontic Program, Shenzhen Stomatological Hospital of Southern Medical University, Shenzhen, China. 6. Professor and Director of Hospital, Shenzhen Stomatological Hospital of Southern Medical University, Shenzhen, China.