Ставропольский государственный медицинский университет, российская Федерация 2 Кубанский государственный медицинский университет, Краснодар, российская Федерация The results of immunohistochemical studies of the pulpal state and vascular endothelium of the dental alveolar complex are presented in the experimental modeling of periodontitis and osteoporosis in sheep. The endothelial structural parameters of PD in animals in the gums of the upper and lower jaws differ and affect the length, thickness of cells, number of mitochondria, Golgi complex, reticulum of the endothelium, relationship between the nucleus and cytoplasm, and amount of heterochromatin in the nucleus. In periodontitis, pathological changes are noted in the endothelial circle, as well as in pericytes; this is manifested by a complex vascular-tissue reaction of the microcirculatory bed of periodontal tissues with a violation of the rheological properties of the blood, combined with the formation of exudate and an inflammatory cell infiltrate. In the early period after the formation of the model of experimental osteoporosis, slight thickening and straightening were observed in the Korff fibers; at 180 days, the APhF exhibited a more linear structure, occasionally forming a finely mottled network that resembled a mosquito net. At 1 year of observation, there was a lack of Korff fibers in the primary substance of the pulp, and significant thickening of the argyrophilic membranes in the vascular endothelium; these are signs of impairment in the metabolism of the tooth pulp.