This study was divided into experimental part of study which was conducted on 75 Wistar rats with the modeled periodontitis and and clinical part of research which included 106 patients with the chronic generalized periodontitis (CGP). The study established an importance of the oxidative stress (both local and systemic) in development and progress of the disease. It is found out that the saliva of rats with the modeled periodontitis there is the reliable increase in the content of total protein, alkaline phosphatase (ALP) and malonic dialdehyde (MDA) in 1.2, 2.6 and 2.8 times respectively, with the reduced activity of catalase in 2.5 times (all p<0.05). It is determined that the gingiva tissue of rats with the modeled periodontitis has the reduced contents of total protein, collagen, elastin and sulfated glycosaminoglycans in 2.8, 1.5, 1.6 and 1.3 times respectively (all p<0.05). It is proved that the antioxidant (AO) therapy normalizes in the rat saliva the content of protein and MDA (decrease in 1,2 and 1,8 times accordingly, p<0.05) and increases the activity of catalase (in 2.5 times, p<0,05). Calcium D3 normalizes the protein content and activity of ALP (decrease in 1.2 and 1.5 times, respectively, p<0.05). It is found out that the saliva of patients with CGP in the acute phase the content of protein, ALP and MDA increases in 1.9, 2.2 and 1.5 times accordingly (p<0,05) with the reduced catalase activity in 1,1 times (p<0,05). It is revealed that the inclusion of CGP patents in AO complex therapy results jointly with the best clinical effect in the more expressed reduction in generation of reactive oxygen species and lipid peroxidation and also the increased plasma APA.