1. Department of Stomatology, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China
2. Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
3. Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, People's Republic of China
4. Laboratory of Tissue Regeneration and Immunology and Department of Periodontics, Beijing Key Laboratory of Tooth Regeneration and Function Reconstruction, School of Stomatology, Capital Medical University, Beijing, People's Republic of China