1. State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases & Department of Cariology and Endodontics & Department of Oral Pathology, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
2. Department of Operative Dentistry and Endodontics, West China School of Stomatology, Sichuan University, Chengdu 610041, China
3. Stomatology Center, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052 Henan, China
4. Department of Endodontics, Periodontics and Prosthodontics, University of Maryland Dental School, Baltimore, MD 21201, USA