1. Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, Jiangsu 210029, P.R. China
2. Department of Anatomy, Histology and Embryology, Nanjing Medical University, Nanjing, Jiangsu 211100, P.R. China
3. Department of Periodontology Nanjing Stomatological Hospital, Medical School of Nanjing University, Nanjing, Jiangsu 210029, P.R. China