1. State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Research Unit of Oral Carcinogenesis and Management, Chinese Academy of Medical Sciences, Med-X Center for Materials, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan 610041, P. R. China
2. College of Stomatology, Chongqing Medical University, Chongqing 401147, China