1. Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi, China.
2. Research and Development Center for Tissue Engineering, Fourth Military Medical University, Xi'an, Shaanxi, China.
3. Department of Oral Histology and Pathology, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi, China.
4. Department of Stomatology, The Third Central Hospital, Tianjin, China.