1. Beijing Research Institute of Traumatology and Orthopaedics, Beijing, PR China
2. Beijing Jishuitan Hospital, Capital Medical University, Beijing, PR China
3. Institute for Laboratory Animal Resources, National Institutes for Food and Drug Control, Beijing, PR China
4. Department of Stomatology, Tsinghua Changgung Hospital, Beijing, PR China
5. Department of Stomatology, the First Medical Center of PLA General Hospital, Beijing, PR China