Received: 10 December 2017 Revised: 12 March 2018 Accepted: 13 March 2018 DOI: 10.1002/JPER.17-0721 2017 WORLD WORKSHOP Periodontitis: Consensus report of workgroup 2 of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions Panos N. Papapanou 1 Mariano Sanz 2 Nurcan Buduneli 3 Thomas Dietrich 4 Magda Feres 5 Daniel H. Fine 6 Thomas F. Flemmig 7 Raul Garcia 8 William V. Giannobile 9 Filippo Graziani 10 Henry Greenwell 11 David Herrera 2 Richard T. Kao 12 Moritz Kebschull 1,13 Denis F. Kinane 14 Keith L. Kirkwood 15 Thomas Kocher 16 Kenneth S. Kornman 9 Purnima S. Kumar 17 Bruno G. Loos 18 Eli Machtei 19 Huanxin Meng 20 Andrea Mombelli 21 Ian Needleman 22 Steven Offenbacher 23 Gregory J. Seymour 24 Ricardo Teles 14 Maurizio S. Tonetti 7 1 Columbia University, New York, NY, USA 2 Universidad Complutense Madrid, Madrid, Spain 3 Ege University, Izmir, Turkey 4 University of Birmingham, Birmingham, United Kingdom 5 Universidade Guarulhos, Guarulhos, Brazil 6 Rutgers University, Newark, NJ, USA 7 University of Hong Kong, Hong Kong, SAR China 8 Boston University, Boston, MA, USA 9 University of Michigan, Ann Arbor, MI, USA 10 University of Pisa, Pisa, Italy 11 University of Louisville, Louisville, KY, USA 12 Private practice, Cupertino, CA, USA 13 Bonn University, Bonn, Germany 14 University of Pennsylvania, Philadelphia, PA, USA 15 University at Buffalo, Buffalo, NY, USA 16 Greifswald University, Greifswald, Germany 17 The Ohio State University, Columbus, OH, USA 18 Academic Center for Dentistry (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, The Netherlands 19 Rambam Health Care Campus & Israel Institute of Technology, Haifa, Israel 20 Peking University, Beijing, China 21 University of Geneva, Geneva, Switzerland 22 University College London, London, United Kingdom 23 University of North Carolina, Chapel Hill, NC, USA 24 University of Queensland, Brisbane, Australia © 2018 American Academy of Periodontology and European Federation of Periodontology J Periodontol. 2018;89(Suppl 1):S173–S182. wileyonlinelibrary.com/journal/jper S173