American Academy of Periodontology Disease Classification

The third learning objective is to understand periodontal disease classification. The AAP updated its classification system for periodontal diseases in 1999 to create a common terminology compatible with scientific knowledge of periodontal diseases.5 Major changes included a new section classifying gingival diseases, replacement of the term “adult periodontitis” with the term “chronic periodontitis” and replacement of the term “early-onset periodontitis,” with the term “aggressive periodontitis.”

Other less commonly occurring categories of periodontitis include disease associated with genetic disorders, necrotizing ulcerative periodontal diseases, abscesses of the periodontium, periodontitis associated with endodontic lesions and developmental or acquired deformities and conditions.

Chronic periodontitis is the most common type experienced by adults and it is known to occur in adolescents as well. Epidemiologic studies currently do not provide enough information to report exact prevalence due to the lack of consistency in study design, outcome measures and endpoints. In the 1996 Annals of Periodontology, Volume 1, Number 1, November, 1996, a review of the published data found that more severe forms of periodontal disease occur in approximately 10% of the population in developed countries, but that moderate attachment loss is more widespread. Variables of age, plaque and bleeding on probing are all found to be related to disease incidence and severity.6 Chronic periodontitis is usually, but not always, a slowly progressing form of periodontitis that often responds to treatment. The rate of progression is neither predictable nor steady. Studies show that patients may experience periods of relative quiescence and bursts of rapidly progressing disease activity.7 Chronic periodontitis can be considered localized (≤ 30% of sites involved) or generalized (> 30% of sites involved). The Update to 1999 Disease Classification24 provides additional parameters for describing localized vs. generalized chronic periodontitis. It recommends that the disease be considered localized if it affects either 1) a clear pattern of the location of affected teeth or 2) >30% of the teeth present. Likewise, it recommends that the disease be considered generalized if it affects either 1)greater than 30% of teeth or 2) with no clear pattern of distribution. Severity can be characterized by the amount of clinical attachment loss (CAL) (Slight = 1-2 mm, Moderate = 3-4 mm, Severe = ≥ 5mm). The Update to 1999 Disease Classification24 also provides additional parameters for determining the severity of periodontitis. One parameter is probing depth, which can be considered slight (>3 & <5 mm), moderate (>5 & <7 mm), or advanced (>7 mm). Another parameter is bleeding on probing which can be another sign of periodontitis of any severity. The third parameter is radiographic bone loss, which can be considered slight (up to 15% of root length or >2 mm & <3 mm), moderate (16% to 30% of root length or >3 mm & <5 mm), and advanced (>30% or >5mm). The addition of these three parameters is helpful because accurate CAL measurements may be difficult to determine clinically.

This course focuses on chronic periodontitis; by far the most common form of the disease.