1. Department of Pediatric Dentistry, Hospital of Stomatology Hebei Medical University, Shijiazhuang, Hebei, China (mainland)
2. Department of Epidemiology and Statistics, School of Public Health, Hebei Medical University, Shijiazhuang, Hebei, China (mainland)
3. Department of Pathology, Hospital of Stomatology Hebei Medical University, Shijiazhuang, Hebei, China (mainland)