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Importance of the Latest Classification System

Dental hygienists may not be aware of the American Academy of Periodontology’s 1999 classification system for periodontal diseases. Gary Armitage, DDS, MS, discusses how the system affects dental hygiene practice.

To read the actual classifications and for more resources regarding the classification system, visit .

Q. What is a disease classification system?

A. Classification systems provide a general frame work>for studying the etiology, pathogenesis, and treatment of diseases. Classification systems, like the one for periodontal diseases, group similar diseases and conditions into general categories. They are useful in studying the full spectrum of diseases in large populations of patients. Disease classification systems differ from diagnoses because diagnoses are applied to individual patients—facilitating the formulation of a treatment plan and addressing specific patient needs. The classification is for a general population. Classification systems are useful in evaluating an optimal treatment for a given group of patients. From a dental practitioner’s point of view, the classification is a starting point for thinking about the periodontal diagnosis of an individual patient.


Q. How was the 1999 classification system for periodontal diseases created?

A. Previous to the current system, the classification of periodontal diseases emerged from the 1989 World Workshop in Clinical Periodontics. However, that classification had many shortcomings. As a result in 1997, the American Academy of Periodontology (AAP) formed a committee to address the problems with the 1989 system. The committee planned an international workshop to revise the classification system for periodontal diseases and conditions.The 1999 workshop was funded by a generous, unrestricted grant from the Colgate-Palmolive Co and its subsidiaryColgate Oral Pharmaceuticals.1  The AAP wanted worldwide input so about half of the 60 participants were from countries besides the United States. The work shop participants discussed the problems of the 1989 version and agreed on a new classification.1  The proceedings were published in the Annals of Periodontology.2

Q What were the problems with the 1989 classification?

A. The 1989 version did not include a gingivitis or a gingival disease category. The periodontitis categories had nonvalidated age-dependent criteria, such as adult periodontitis and juvenile periodontitis. In addition, extensive crossover existed in the rates of progression and other clinical characteristics of the different categories of periodontitis. For example, “rapidly progressive periodontitis” clearly was not a single disease. Workshop participants also recognized that refractory periodontitis was not a stand-alone disease category, but rather, a collection of conditions, and that prepubertal periodontitis was not a single disease entity.


Q. How did the 1999 classification address these problems?

A. One solution was to add a complete gingival disease category. More than 50 different conditions are now listed in the classification for gingival diseases. Regarding the nonvalidated age-dependent criteria, two questions that arose were what defines an adult and what defines a juvenile? Does adult periodontitis begin at age 18 or 21? Should a legal or biological definition of an adult be used? This makes it very difficult to decide on how to classify the disease if age is used as a criterion. In the 1989 classification, periodontitis patients who were 35 years and older were classified as having adult periodontitis. The arbitrary use of 35 years of age as an important disease classification criterion created a lot of criticism. Then came the issue of defining a juvenile—13-year-olds are certainly juveniles but what about 18-year-olds? Did their disease change once they got older? Because of these problems, it was decided to eliminate the use of adult and juvenile as descriptors. Much time was spent on what terms to use in place of adult and juvenile. Chronic replaced adult and aggressive replaced juvenile.

In the 1989 classification system there was a separate category called “rapidly progressive periodontitis.” However, it is now known that several forms of periodontitis can undergo short periods of rapid progression, eg, 2 mm of clinical attachment loss in a 3-month period. Therefore, the term “rapidly progressive periodontitis” was eliminated.

There’s been some confusion about what happened to the refractory periodontitis category. It was determined that refractory periodontitis wasn’t a single disease group so it was eliminated as a stand-alone category. However, it is still acknowledged that all forms of periodontitis can be nonresponsive to conventional treatment. For example, under the current system it is possible to have patients with “refractory chronic periodontitis” or “refractory localized aggressive periodontitis.”

The prepubertal periodontitis category was eliminated. In reality, many patients with prepubertal periodontitis have systemic diseases such as leukocyte adherence deficiency, hypophosphatasia, cyclic neutropenia, or congenital primary immunodeficiency. What was originally described as prepubertal periodontitis was actually a collection of periodontal manifestations of different systemic diseases. It was also recognized, based on epidemiologic data, that some children and adolescents develop what clinically appears to be chronic periodontitis.3 Epidemiologic data also suggest that aggressive periodontitis might begin at an early age.4-6

Q. Do the changes in the classification affect insurance reimbursement?

A. Any classification system should not disenfranchise or make problems for practitioners in reimbursement procedures. Members of the AAP Patient Benefits and Advocacy Advisory Committee attended the 1999 workshop. They wanted to make sure that whatever emerged didn’t make it difficult for practitioners to receive payment.

Regarding the Case Type (I-V) classification system, it never had any biological basis. It was primarily intended for insurance purposes. Unfortunately, some dental and dental hygiene schools taught it as a diagnostic classification. Many insurance companies still cling to the terminology. This is probably fine as long as dentists and dental hygienists don’t think it is a valid biological system of classification. The system is nothing more than insurance company paperwork. I know that some insurance companies are moving away from the I-V system.

Q. Should we consider treating periodontal diseases sooner or more rigorously now that they are reclassified?

AIn my view, the new classification system is simply a refinement, rather than going in an entirely new direction. A revolutionary classification did not emerge from the workshop. Some terms were changed and some regrouping was done to make the categories biologically less problematic. Therefore, treatment decisions should be based on the needs of the individual patient and the skill level of the practitioner. Referral to a periodontist is always an option and should be considered when appropriate.

Q. Will there be more changes in the future?

A. Yes, many scientists are currently working on how to separate the various categories of chronic periodontitis on the basis of biological differences. What is now called chronic periodontitis is probably more than one disease. Chronic periodontitis is a group of infections that involve many kinds of bacteria, rather than a few. In addition, there are significant variations in host susceptibility that will eventually become part of a new system of classification. The same is true with localized aggressive periodontitis. The current data indicate that it’s probably more than one specific disease.7 It will probably be at least a decade before we have enough information to classify periodontal diseases on firm evidence-based biological characteristics.



  1. Armitage GC. Development of a classification system for periodontal diseases and conditions. Ann Periodontol. 1999;4:1-6.
  2. American Academy of Periodontology. 1999 International Workshop for a Classification of Periodontal Diseases and Conditions. AnnPeriodontol. 1999;4:1-112.
  3. Albandar JM, Tinoco EMB. Global epidemiology of periodontal diseases in children and young persons.Periodontol 2000. 2002;29:153-176.
  4. Sweeney EA, Alcoforado GAP, Nyman S, Slots J. Prevalence and microbiology of localized prepubertal periodontitis. Oral Microbiol Immunol. 1987;2:65-70.
  5. Bimstein E, Delaney JE, Sweeney EA. Radiographic assessment of the alveolar bone in children and adolescents.Pediatr Dent. 1988;10:199-204.
  6. Sjödin B, Matsson L. Marginal bone loss in the primary dentition. A survey of 7–9-year-old children in Sweden.  Clin Periodontol. 1994;21:313-319.
  7. Li Y, Xu L, Hasturk H, Kantarci A, DePalma SR, Van DykeTE. Localized aggressive periodontitis is linked to human chromosome 1q25. Hum Genet. 2004;114:291-297.

From Dimensions of Dental Hygiene. June 2005;3(6):18, 20-21.

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