1. Department of Geriatric Dentistry, Peking University School and Hospital of Stomatology, Beijing, People's Republic of China.
2. First Clinical Division, Peking University School and Hospital of Stomatology, Beijing, People's Republic of China.
3. Department of Dental Materials, Peking University School and Hospital of Stomatology, Beijing, People's Republic of China.
4. Central Laboratory, Peking University School and Hospital of Stomatology, Beijing, People's Republic of China.
5. Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, People's Republic of China.
6. National Engineering Laboratory for Digital and Material Technology of Stomatology, Peking University School and Hospital of Stomatology, Beijing, People's Republic of China.