Epidemiologic patterns of chronic and aggressive periodontitis.

The currently used definitions of chronic and aggressive periodontitis were introduced at the 1999 World Workshop for the Classification of Periodontal Diseases and Conditions (2). This revised classification system was meant to address a number of widely recognized shortcomings of the 1989 World Workshop diagnostic scheme, according to which the majority of the pathologic periodontal conditions were classified under three main categories: ‘Early Onset Periodontitis’, ‘Adult Periodontitis’, and ‘Refractory Periodontitis’. The 1999 classification did indeed address some key deficiencies of the earlier system including (i) the lack of a diagnostic category describing exclusively gingival lesions, (ii) the dependence on knowledge about the time of disease onset for distinguishing between ‘Early Onset-’ and ‘Adult’ periodontitis, and (iii) the highly heterogeneous ‘Refractory Periodontitis’ group, a term whose appropriate use required prior knowledge of the volume and quality of therapy rendered, as well as of patient compliance. Nevertheless, although one of the 1999 Classification’s explicitly expressed goals was “to discard classification terminologies that were age-dependent or required knowledge of rates of progression” (5), the new system admittedly offered only limited substantial improvement on either front. For example, one of the primary features of the newly introduced ‘Aggressive Periodontitis’ is “rapid attachment loss and bone destruction” (33). With respect to age, “circumpubertal onset” continues to constitute a key feature of Localized Aggressive Periodontitis, while Generalized Aggressive Periodontitis is suggested to “usually affect persons under 30 years of age, but patients may be older” (33). Considering that another primary diagnostic feature of Aggressive Periodontitis is “familial aggregation” of the disease, a feature that is often impossible to ascertain upon examination of a patient, one quickly recognizes that appropriate assignment of this particular diagnosis by the clinician –let alone by the epidemiologist- remains highly problematic. Nevertheless, use of the search terms ‘chronic periodontitis’ and ‘aggressive periodontitis’ in the PubMed database alone at the time of authorship of this text (July 2009) identified approximately 3,300 and 1,650 publications, respectively. Interestingly, articles using the term ‘chronic periodontitis’ covered a time span dating back to 1948, while the earliest indexed publication retrieved using ‘aggressive periodontitis’ as a keyword was published the same year, indicating that these terms have been obviously used in a variety of different contexts. Hence, given the substantial body of literature using these terms and in order to contrast with earlier reviews of the epidemiology of periodontitis that heavily relied on publications employing terminology no longer in use (9, 41), we decided to limit the present text to epidemiologic studies published over the past decade, anticipating that they would have utilized the 1999 World Workshop nomenclature. For an overview of the literature prior to 1999, the reader is referred to the above earlier quoted texts. In our review, we first address some methodological considerations related to the assessment of chronic and aggressive periodontitis in epidemiologic studies. We particularly address the issue of disease onset and the impact of age in the determination of diagnosis. Subsequently, we present current data on the global prevalence of destructive periodontitis and its variability with respect to demographic characteristics. Our review does not include the study of diagnosis-specific genetic and environmental risk factors for chronic or aggressive periodontitis, as these are dealt with in detail in Chapter 10.