Introduction. The aim of the present paper was to study the peculiarities of the composition of the oral fluid (OF) in children affected by dental enamel hypoplasia (DEH). Material and methods. In the case-control study were clinically examined 78 children between the ages of 6 and 18. IN the research group (L1) were included 39 children with DEH. The control group (L0) consisted of 39 conventionally healthy children. In order to highlight the particularities of of composition in children with DEH were studied biochemical markers of phosphor-calcium bone metabolism. The dosage of Ca, Pi, tartrate-resistant acid phosphatases and thermolabile alkalis was performed with standard kits EliTech (France), osteocalcin dosing was performed immunoenzymatically (ELISA) with the DSL-10-7600 ACTIVE Human Osteocalcin Enzyme-linked Immolunosorbent Assay produced by Diagnostic Systems Laboratories Inc. (USA). Results. The study detected in OF the reduced activity of thermolabile alkaline phosphatase (ALP), the statistically significant increase in the activity of tartrate-resistant acid phosphatase (TRAP), the statistically significant decrease in the level of Vitamin D3, as well as the significant reduction of the Ca/Pi ratio in OF. Conclusions. The study of the particularities of the OF composition in children affected by DEH detected the deregulation of bone and phosphor-calcium metabolism which represents an important caries risk factor and highlighted the need for deepening interdisciplinary studies to argue for the complex approach in planning preventive measures, developed by multi-purpose teams of medical specialists.