1. State Key Laboratory of Organic‐Inorganic CompositesBeijing University of Chemical Technology Beijing 100029 P. R. China
2. Beijing Laboratory of Biomedical MaterialsBeijing University of Chemical Technology Beijing 100029 P. R. China
3. Department of Mechanics and Engineering ScienceCollege of EngineeringPeking University Beijing 100871 P. R. China
4. Department of EndodonticsSchool and Hospital of StomatologyTianjin Medical University Tianjin 300070 P. R. China
5. Department of Spine SurgeryBeijing Jishuitan Hospital Beijing 100035 P. R. China