1. State Key Laboratory of Military Stomatology, Department of Prosthetics, School of Stomatology, The Fourth Military Medical University, Xi’an, Shaanxi, P.R. China,
2. Shaanxi Key Laboratory of Stomatology, Xi’an, Shaanxi, P.R. China, and
3. State Key Laboratory of Military Stomatology, Center for Tissue Engineering, School of Stomatology, The Fourth Military Medical University, Xi’an, Shaanxi, P.R. China