1. Department of Geriatric Dentistry, Peking University School and Hospital of Stomatology, Beijing 100081, China
2. State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
3. The Oral Clinic of the 2nd Hospital of Beijing Armed Police Force, Beijing 100037, China
4. National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing 100081, China