Introduction: Colonization resistance of the oral cavity is an important protective factor of local immunity, which prevents the adhesion and proliferation of microorganisms on the oral mucosa.Objectives: The research aimed to discover the colonization resistance state of the oral mucosa of young patients with different body mass indices and their dependence on the intensity of the teeth carious and inflammatory response of the gums. Material and methods:The survey conducted on 132 Ukrainians of all genders, with aged ranging from 18 to 22 years. Body mass index (BMI) was determined, which was the distribution factor. Oral status was detected by decay, missing, and filled teeth (DMFT) index, oral hygiene index (OHI) and papilla bleeding index (PBI) determination. Colonization resistance of the oral mucosa was defined by microscopy of the buccal epithelium using a light microscope with a magnification of ×400. Results: 21.2% of patients with normal BMI had colonization resistance index (CRI) 0, 78.8% -CRI 1. In patients with extra weight, 44.5% had CRI 0, 38.9% -CRI 1, 16.6 -CRI 2. In patients with 1 st degree obesity, 64.5% had CRI 0, 25.8% -CRI 1, 9.7% -CRI 2. In patients with 2 nd degree obesity, 68.75% presented CRI 0, 31.25% -CRI 1. Conclusions: With satisfactory oral hygiene in patients with diverse BMI the severity of gingivitis was different. This indicates that the systemic response of the organism in patients with BMI over 30 kg/m 2 is the crucial determining factor that influences the manifestation of the disease, as a response to local pathogenic factor -dental plaque. Therefore, in patients with 1 st and 2 nd degree obesity, in 70% of patients, suppression of colonization resistance of the oral mucosa was observed, compared with patients with normal BMI where the frequency of patients with colonization resistance disturbance was 2.5 times lower.

The oral cavity is a unique environment that consists of teeth surrounded by periodontal tissues, oral mucosae with minor salivary glands, and terminal parts of major salivary glands that open into the oral cavity. The cavity is constantly exposed to viral and microbial pathogens. Recent studies indicate that components of the plasminogen (Plg)/plasmin (Pm) system are expressed in tissues of the oral cavity, such as the salivary gland, and contribute to microbial infection and inflammation, such as periodontitis. The Plg/Pm system fulfills two major functions: (a) the destruction of fibrin deposits in the bloodstream or damaged tissues, a process called fibrinolysis, and (b) non-fibrinolytic actions that include the proteolytic modulation of proteins. One can observe both functions during inflammation. The virus that causes the coronavirus disease 2019 (COVID-19) exploits the fibrinolytic and non-fibrinolytic functions of the Plg/Pm system in the oral cavity. During COVID-19, well-established coagulopathy with the development of microthrombi requires constant activation of the fibrinolytic function. Furthermore, viral entry is modulated by receptors such as TMPRSS2, which is necessary in the oral cavity, leading to a derailed immune response that peaks in cytokine storm syndrome. This paper outlines the significance of the Plg/Pm system for infectious and inflammatory diseases that start in the oral cavity.