1. College of Biomedical Engineering School of Chemical Engineering West China Hospital of Stomatology State Key Laboratory of Oral Diseases Sichuan University Chengdu 610065 P. R. China
2. State Key Laboratory of Oral Diseases National Clinical Research Center for Oral Diseases Department of Orthodontics and Pediatric Dentistry West China Hospital of Stomatology Sichuan University Chengdu 610065 P. R. China
3. State Key Laboratory of Oral Diseases National Clinical Research Center for Oral Diseases Department of Orthodontics West China Hospital of Stomatology Sichuan University Chengdu 610065 P. R. China
4. Department of Materials Imperial College London London SW7 2AZ UK
5. Department of Biomedical Engineering The City College of the City University of New York New York NY 10031 USA
6. State Key Laboratory of Polymer Materials Engineering Sichuan University Chengdu 610065 P. R. China
7. Department of Mechanical Engineering The University of Hong Kong Hong Kong 999077 P. R. China