1. Department of Pediatric Dentistry, School of Dentistry, Medical College of Georgia, 1459 Laney Walker Blvd., Augusta, GA 30912-1210, USA; and
2. College of Dentistry, University of Illinois at Chicago, 801 S. Paulina Street, Room 458, Chicago, IL 60612, USA, and Department of Cariology, West China College of Stomatology, Sichuan University, Renmin Nan Road Section 3 14#, Chengdu, Sichuan 610041, China