1 Department of Stomatology, Affiliated Hospital of Jining Medical University, Jining, China.
2 Division of Endodontics, Department of Oral Biological & Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, Canada. Electronic address: he.liu@ubc.ca.
3 Division of Endodontics, Department of Oral Biological & Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, Canada.