1. Department of Orthodontics, Fourth Military Medical University, Xi’an, Shaanxi, People’s Republic of China.
2. Research and Development Center for Tissue Engineering, Fourth Military Medical University, Xi’an, Shaanxi, People’s Republic of China.
3. Department of Oral Histology and Pathology, School of Stomatology, Fourth Military Medical University, Xi’an, Shaanxi, People’s Republic of China.