Introduction

Clinicians and students worldwide have looked upon the American Academy of Periodontology (AAP) and the European Federation of Periodontology (EFP) as the world leaders in the classification of periodontal diseases for several decades. Given that the last published classification of periodontal disease prior to 2018 was in 1999,1 their decision in 2015 to commence planning a new World Workshop to modernize the classification based on more current research findings was determined to be warranted. There are numerous reasons why an international periodontal classification system is required, all of which are important. A classification system provides an international language for both research and communication in order to facilitate population surveys of disease prevalence, natural history, etiology and pathogenesis. Additionally, a standardized case definition of periodontal disease is critical to allowing more homogeneity in research protocols such as determination of the effectiveness of treatment modalities as well as in oral-systemic research in order to provide more consistent evidence to determine the nature of these relationships. A common system also enables diagnosis, risk assessment, and prognostication in order to educate and communicate with patients, and most importantly, to ensure implementation of appropriate treatment.

After 2 years of intensive planning, the World Workshop was held in Chicago November 9–11, 2017.2,3 Nineteen review papers and 4 Consensus Reports were commissioned by the AAP/EFP organizing committee with a focus on not only updating/revision of the 1999 classification, but to also include peri-implant diseases and conditions.2,3 These workgroups were also asked to establish both case definitions and diagnostic criteria to assist clinicians with the use of the new system. The 4 Working Groups commissioned with the creation of the Consensus Reports were divided as follows:

  • Working Group #1: Periodontal Health and Gingival Diseases and Conditions on an Intact and a Reduced Periodontium
  • Working Group # 2: Periodontitis
  • Working Group # 3: Periodontal Manifestations of Systemic Diseases and Developmental and Acquired Conditions
  • Working Group #4: Peri-implant Diseases and Conditions

This classification system is based on these 4 categories encompassing the most current literature available. In particular, the creation of the new system was driven by a focus on the findings from the Human Microbiome Project; the World Health Organization’s definition of Health; new discoveries on Inflammation; and on the concept of Precision/Personalized Medicine.

A major change from the 1999 Classification was required as advances in scientific research provided new evidence from multiple sources such as basic science investigations, population studies and prospective studies that evaluated both environmental and systemic risk factors. The first major change was to address some of the unresolved issues with the previous classification. The previous classification did not identify parameters for gingival health or gingivitis in an intact or reduced periodontium. This led to a lack of clarity regarding classification of diagnosis given the presence of gingival inflammation at one or more sites and a patient-level definition of gingivitis. Thus, a definition for periodontal health was included in this classification, which serves as a treatment endpoint goal and a benchmark for contrast with disease processes. In this classification, bleeding on probing was identified as the primary parameter to set thresholds for gingivitis.2-5 The new classification also differentiates gingival health and gingival inflammation occurring on an intact periodontium from that found on a reduced periodontium, which could be present on either a stable periodontitis patient or a non-periodontitis patient, in whom attachment was not lost due to inflammatory periodontitis.2,3 It is well-established that gingivitis is reversible and therefore that a gingivitis patient can revert to a state of health. In a patient who has lost attachment due to inflammatory periodontitis, they always remain at an increased risk of further attachment loss and therefore, despite successful therapy, a periodontitis patient remains one for life and requires lifelong supportive care.2,3 Introduction and incorporation of a system of staging and grading based on medical systems for symptomatology and risk stratification, such as those for hypertension and/or oncology, is another major change in this classification of periodontitis. Lastly, the inclusion of a classification for peri-implant health and diseases was a de novo addition to the new classification system.