One of the factors in the development of dental caries in children with malocclusion is the insufficient enamel mineralization in different age periods, that is, its resistance is reduced. An important role in the formation of enamel resistance is played by the oral fluid, in particular its physical properties, mineralization potential and protective mechanisms. Fluctuations in the pH of the oral fluid significantly depend on the hygienic condition of the oral cavity and the nature of the food. At the same time, the possibility of access of mineral elements to the surface of the enamel significantly worsens in case of increased viscosity and decreased rate of saliva secretion of oral fluid. This, in turn, contributes to the reduction of diffusion processes in tooth enamel and the creation of conditions for the development of enamel demineralization. The purpose of the investigation is to study the peculiarities of the physical properties of oral fluid in children with malocclusion at different levels of enamel resistance. Research methods. It was found that the concentration of hydrogen ions in the oral fluid of the examined children with malocclusion is, on average, 6.67±0.05 units, and the viscosity and rate of saliva secretion is 2.32±0.06 rel. unit and 0.43±0.02 ml/min. In children with anomalies of individual teeth, the average pH value of the oral fluid is 6.93±0.08 units, while with anomalies of the dental arches and occlusion, there is a shift of the pH to the acidic side. In 12and 15-year-old children with anomalies of occlusion and caries-resistant enamel, the pH of the oral fluid is higher by 7.46% and 7.85%, respectively, compared to children with conditional-resistant and caries-susceptible enamel, the viscosity of the oral fluid is lower by 40.49% and 33.48%, respectively, and the rate of salivation is higher by 26.19% and 22.92%, which changes the function of oral fluid in the latter towards the demineralizing solution. Conclusions. Thus, the detected changes in the physical properties of the oral fluid in children with malocclusion and reduced enamel resistance may be important in the pathogenesis of dental caries development, as in such conditions the function of the oral fluid changes from mineralizing to demineralizing.