Microvasculature in gingivitis and chronic periodontitis: disruption of vascular networks with protracted inflammation.

Gingivitis occurring when bacterial plaque accumulates in the gingival crevice provides a convenient and interesting model for chronic inflammation in humans. In some patients, gingivitis progresses to the destructive lesion of periodontitis, involving the formation of periodontal pockets. The basis for pocket formation and progression is not as yet clear, although neutrophilic polymorphonuclear leukocytes (PMN) appear to play a protective role. Vascular changes appear to either facilitate or inhibit PMN function with the effect of either protecting from, or stimulating, periodontitis. Contrary to most circumstances, high endothelial cells in periodontitis are involved with PMN rather than lymphocyte emigration. Expansion of the microvasculature through increased vascular diameter and tortuosity as well as the development of high endothelial cells appears to protect from periodontitis by increasing the supply of both plasma defense factors and PMN to the tissues. Vascular changes that may oppose this and promote periodontitis are the formation of perivascular hyaline material and accumulation of basement membrane rests. The inadequate tissue turnover that accumulation of these vascular products represents can be argued as a vascular response to a chronic inflammation that has failed to eliminate the irritant. It is suggested that these vascular changes may account for the highly localized and burst-like pattern of pocket formation in periodontitis. Finally, it is possible that the recent observation that periodontitis is an independent risk factor for systemic vascular disease may reflect stimulation of acute phase protein synthesis by cytokines released by periodontal high endothelial cells.