The leading factor for improving the management of the pathological process that occurs in periodontal diseases is the understanding of the pathogenesis of the disease. Pathogenesis implies processes that gradually lead to the development of the disease, violating the structure and function of the periodontal. (1) Periodontal diseases tend to develop under the combined influence of general and undoubtedly local factors against the background of reactivity of the body. (3) A pathognomonic sign of periodontitis is the presence of a periodontal pocket, which occurs as a result of atrophy of the gingival pocket and the alveolar process. This article presents an overview of the data of domestic and foreign literature, etiological factors leading to the formation of periodontal pocket, the mechanism of its development from the point of view of modern dentistry.