1. State Key Laboratory of Oral Diseases National Clinical Research Center for Oral Diseases West China Hospital of Stomatology Sichuan University Chengdu Sichuan 610041 P. R. China
2. State Key Laboratory of Oral Diseases West China Hospital of Stomatology Sichuan University Chengdu 610041 P. R. China
3. College of Biomedical Engineering Sichuan University Chengdu 610041 P. R. China