1. First Clinical Division, Peking University School and Hospital of Stomatology, Beijing, China
2. Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
3. Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing, China
4. Laboratory of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing, China