Aim: to assess the caries risk and study the particularities of oral fluid microcrystallization in children. Identifying caries risk factors using the Cariogram software is an important measure which contributes to best understanding of the cariogenic profile of the with fixed orthodontic apppliances. The clinical data of this study is based on the examination of 100 children aged 7-10. The complex evaluation of caries risk was performed using the Cariogram software. The study of crystallographic changes of the oral fluid in children with dental caries and in caries free ones was performed using the method developed by Shatohina S. et al., 2006. Oral fluid (OF) was collected with a sterile pipette in the amount of 0.2-0.3 ml from the oral cavity floor. Then, three drops of oral liquid have been applied on a glass slide. Dehydration of OF drops happened in the thermostat at t 37°C, being protected from dust. Micropreparations have been examined with the optical microscope. The study was conducted in accordance with the requirements of the Code of Ethics for scientific research. The influence of a series of factors was found in the majority of children with fixed orthodontic apppliances. A very low risk in caries was determined in 14% of the children, low risk - in 25%, medium – 28%, high – 17% and very high - 16%. An extreme caries risk was caused by deficient oral hygiene, high concentration of Streptococcus Mutans in saliva, lack of fluoridation etc. The degree of microcrystallization of oral liquid in children with high and very high carious lrisk was 1.9 and 2.4 times lower than the same indicator considered in caries-free children, which was correlated with the duration of dental caries and the work of caries process The study of structural particularities of dehydrated droplet of oral liquid in children with dental caries has elucidated a number of markers of the changes produced in the oral cavity that can be applied later in the screening research in dental practice, development of cariopreventive measures and evaluation of their effectiveness. The high risk in caries occurrence in children indicates the need of initiation of prevention programs targeting individual factors of caries development.