1. State Key Laboratory of Oral Diseases; West China Hospital of Stomatology, Sichuan University; Chengdu 610041 China
2. Department of Operative Dentistry and Endodontics; West China Hospital of Stomatology; Sichuan University; Chengdu 610041 China
3. Department of Biomedical Polymers and Artificial Organs; College of Polymer Science and Engineering; Sichuan University; Chengdu 610065 China