1. Department of Operative Dentistry and Endodontics, School of Stomatology, The Fourth Military Medical University, Xi’an, Shaanxi, China
2. Department of Microbiology, The Forsyth Institute, Cambridge, Massachusetts, USA
3. Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, Massachusetts, USA
4. School of Dentistry, UCLA, Los Angeles, California, USA