1. Department of Stomatology,
Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, P. R. China
2. State Key
Laboratory of High Performance Ceramics and Superfine Microstructure,
Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, P. R. China
3. University of Chinese Academy of Science, Beijing 100049, P. R. China