1. Stomatological Hospital of Chongqing Medical University Chongqing 401147 P.R. China
2. Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education Chongqing 401147 P.R. China
3. Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences Chongqing 401147 P.R. China