1. Research and Development Center for Tissue Engineering, School of Stomatology, The Fourth Military Medical University, Xi'an, People's Republic of China.
2. Department of Oral Histology and Pathology, School of Stomatology, The Fourth Military Medical University, Xi'an, People's Republic of China.
3. State Key Laboratory of Oral Disease, Sichuan University, Chengdu, People's Republic of China.
4. Department of Orthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, People's Republic of China.