1. Department of Prosthodontics, School and Hospital of Stomatology, Peking University, Beijing, P.R. China.
2. Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing, P.R. China.
3. National Engineering Laboratory for Digital and Material Technology of Stomatology, School and Hospital of Stomatology, Peking University, Beijing, P.R. China.