1. Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China
2. School of Dentistry, University of California at San Francisco, California, USA
3. Department of Dental Medicine, Division of Periodontology, Karolinska Institutet, Stockholm, Sweden
4. European Research Group on Periodontology, Berne, Switzerland
5. School of Dental Medicine, State University of New York at Stony Brook, New York, USA