Loos, B. G. & Van Dyke, T. E.


Patients with periodontitis show inflammatory destruction of the supporting tissues around the teeth. Loss of connective tissue and collagen in the gingiva is characteristic, along with loss of periodontal ligament and resorption of alveolar bone. Thus the tooth roots become exposed to the oral environment, and the root and root cementum are colonized with a bacterial biofilm, which can calcify to form dental calculus. The chronicity and mostly slow progression of this disease results in tooth mobility, loss of chewing function, esthetic disturbances and, ultimately, if left untreated, tooth exfoliation. Moreover, periodontal inflammation has systemic effects; it can induce low grade systemic inflammation, which has negative effects on other organs.

Traditionally, the most common forms of periodontitis have been separated into 2 types: aggressive periodontitis and chronic periodontitis.1 However, it has recently been acknowledged that the scientific basis for this classification is weak and based on a variable clinical presentation.2-5 In particular, in light of the complexity of the causative factors for periodontitis that will be discussed in this paper, the distinction between various clinical presentations has been removed. The shortcomings of clinical diagnoses included substantial overlap and lack of clear pathobiology‐based distinctions between the stipulated categories, diagnostic imprecision, and treatment implementation difficulties. Although the 1999 classification1 provided a workable framework that has been used extensively in both clinical practice and scientific investigations in periodontology during the past 17 years, the shortcomings were deemed too great for further utility, and a new classification was introduced.

Epidemiological research has shown that severe periodontitis occurs in about 7%‐14% of the population in western Europe and North America, depending on the definitions used for severe periodontitis, and depending on the specific study population evaluated. In populations and countries with low availability of dental care with limited dental health awareness, and when limited preventive measures are available, the prevalence of severe periodontitis may be 10%‐15%.9 It may well be that the genetic susceptibility factors are more pronounced in certain racial/ethnic populations; the prevalence of severe periodontal disease in central and east sub‐ Saharan Africa, and within some racial/ethnic groups in the USA, was found to be up to 20%.

Periodontology 2000, 83(1), 26–39