1. Physical Examination Center, West China Hospital, Sichuan University, Chengdu 610041, P. R. China
2. College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, P. R. China
3. State Key Laboratory of Oral Diseases, Med-X Center for Materials, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, P. R. China