1. Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, 22 Zhongguancun South Street, Haidian District, Beijing, China
2. Department of Dental Materials, Peking University School and Hospital of Stomatology, 22 Zhongguancun South Street, Haidian District, Beijing, China
3. Department of Geriatric Dentistry, Peking University School and Hospital of Stomatology, 22 Zhongguancun South Street, Haidian District, Beijing, China