Special Issue:Proceedings of the World Workshop on the Classification of Periodontal and Peri‐Implant Diseases and Conditions. Co‐edited by Kenneth S. Kornman and Maurizio S. Tonetti. The workshop was planned and conducted jointly by the American Academy of Periodontology and the European Federation of Periodontology with financial support from the American Academy of Periodontology Foundation, Colgate, Johnson & Johnson Consumer Inc., Geistlich Biomaterials, SUNSTAR, and Procter & Gamble Professional Oral Health. All manuscripts were fully peer reviewed.