Bacterial mediators in periodontal disease.

Periodontal disease is the general description given to the inflammatory response of the gingiva and underlying connective tissue to bacterial accumulations (dental plaque) on the teeth. A limited number of cultivable species are usually associated with periodontal disease. The majority of putative periodontal pathogens are gram-negative anaerobic rods. Some of the characteristics of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Treponema denticola will be discussed, given their prominence in the literature. These organisms share the ability to penetrate the gingival epithelium, such that their endotoxins, immunologically active compounds, and cytotoxic enzymes and molecules are presented directly to the host's inflammatory cells. This ability may be what distinguishes these gram-negative species from the plethora of other gram-negative species that inhabit the subgingival plaque. In addition, these organisms tend to be selected for in disease-associated plaques, suggesting that their nutritional needs are met when the gingival crevicular fluid contains a variety of inflammatory mediators and products of tissue breakdown. A. actinomycetemcomitans produces a leukotoxin, and the immunologic response of the host to this antigen may explain the unique pattern of tooth involvement in localized juvenile periodontitis. Both P. gingivalis and T. denticola have a trypsin-like enzyme that could be a virulence factor, primarily because this enzyme(s) may allow these organisms to grow in the presence of the inflammatory response of the host.