Ke Deng1,2, George Pelekos1, Lijian Jin1, Maurizio S Tonetti1,2,3. 1. Division of Periodontology and Implant Dentistry, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China. 2. Department of Oral and Maxillofacial Implantology, National Clinical Research Center of Stomatology, Ninth People' Hospital, College of Medicine, Shanghai Jiao Tong University, Shanghai, China. 3. European Research Group on Periodontology, Genoa, Italy.