1. Department of Cariology and Endodontology Peking University School and Hospital of Stomatology Beijing China
2. Minnesota Dental Research Center for Biomaterials and Biomechanics School of Dentistry University of Minnesota Minneapolis USA
3. Division of Endodontics Department of Restorative Sciences School of Dentistry University of Minnesota Minneapolis USA
4. Department of Stomatology Affiliated Hospital of Qingdao University Qingdao China