Purpose: to study the effect of type 2 diabetes mellitus on the state of the mucous membrane and tissues of the oral cavity to optimize the prevention and increase the effectiveness of dentition defects complex treatment in this contingent of patients. Materials and methods. We examined 112 patients with type 2 diabetes mellitus aged 35 to 64 years, who were further divided into three groups. The state of the oral mucosa, morphological changes, local immunity, lysozyme were determined. The work used morphological, microscopic methods, enzyme immunoassay and spectrophotometry. To test the statistical significance of intergroup differences, the nonparametric Mann- Whitney test was used. Results. Oral use in patients with diabetes mellitus type 2, applications of 1% Clotrimazole cream and Echinacea Compositum S had a positive preventive and therapeutic effect, which was accompanied by an increase in capillary resistance, a decrease in the degree of migration of leukocytes, an increase in the functional activity of immune system cells and an increase in the level of regenerative processes. In patients with defects in the dentition against the background of type 2 diabetes mellitus, violations of the oral cavity local immunity were revealed, characterized by a significant increase in the S-IgA content and a decrease in lysozyme.Orthopedic treatment with partial removable denturesled to a significant decrease in the concentration of S-IgA and an increase in the bactericidal activity of saliva due to increased lysozyme synthesis. It was concluded that type 2 diabetes mellitus affects the state of the oral mucosa, which must be taken into account when providing orthopedic and dental treatment.