Classification of periodontal diseases

The term periodontal diseases has had somewhat differing connotations over time, as discussed by Loe in the preceding chapter. A continuing concern in classification is whether to include only diseases that have primary manifestation and etiology in the periodontium or whether to also include periodontal manifestations of systemic diseases. Similarly, there may be questions about the propriety of including other conditions that present in the periodontium but do not involve primarily the marginal tissues. Regardless of academic considerations for such distinctions, clinicians must account for all potential abnormalities when formulating a differential diagnosis. The classification presented in this chapter therefore is meant to be relatively inclusive rather than restrictive. It is also based on certain other principles, including that: a) the periodontal diseases that progress from the marginal gingiva are infectious diseases (471, that is, they are caused by bacteria (148); b) inflammatory conditions restricted to the gingiva itself fit within the defining term gingivitis, whereas inflammations extending deeper to involve periodontal ligament, cementum or alveolar bone fit within the term periodontitis (124); and c) although both gingivitis and periodontitis of local origin can be influenced in their expression by systemic conditions and some gingival abnormalities may be caused primarily by systemic conditions, no periodontitis has been documented to be purely of systemic origin (47). Finally, this classification accepts occlusal trauma (and its synonyms for the changes that occur in the periodontium subsequent to +abnormally large forces transmitted to it through the teeth) as a physiological adaptation rather than a disease (32). It is thus not included as an entity in the classification. Actually formed in many ways by numerous investigators and authors over a number of years, the classification presented (Table 1) is only slightly modified from that published earlier in Advances in Dental Research (124). The text below follows the outline of Table 1.