1. Department of orthodontics, Peking University School and Hospital of Stomatology, Haidian District, PR. China
2. National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology, Haidian District, PR. China
3. Department of Orthodontics, University of Florence, Italy
4. Central Laboratory, Peking University School and Hospital of Stomatology, Haidian District, PR. China