1. Department of orthodontics, Tianjin Stomatological Hospital , Tianjin , China
2. School of Medicine, Nankai University , Tianjin , China
3. Tianjin Key Laboratory of Oral and Maxillofacial Function Reconstruction , Tianjin , China
4. Department of Orthodontics, Stomatological Hospital, School of Stomatology, Southern Medical University , Guangzhou, Guangdong , China