1. Department of Endodontics, Fourth Military Medical University, Xi'an, Shaanxi, China.
2. Department of Oral Histology and Pathology, Fourth Military Medical University, Xi'an, Shaanxi, China.
3. Department of Research and Development Center for Tissue Engineering, Fourth Military Medical University, Xi'an, Shaanxi, China.
4. Department of Orthodontics, College of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi, China.
5. Department of Stomatology, General Hospital of PLA, Beijing, China.
6. Department of Periodontology and Oral Medicine, College of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi, China.