Lang Lei1, Fuhua Yan2, Houxuan Li3, Huang Li1. 1. Department of Orthodontics, Nanjing Stomatological Hospital, Medical School of Nanjing University, Nanjing, Jiangsu 210008, China. 2. Department of Periodontics, Nanjing Stomatological Hospital, Medical School of Nanjing University, Nanjing, Jiangsu 210008, China. 3. Department of Periodontics, Nanjing Stomatological Hospital, Medical School of Nanjing University, Nanjing, Jiangsu 210008, China. lihouxuan3435_0@163.com.