The results of some studies indicate that strontium may participate in the processes of enamel remineralisation. Objectives: the effects of strontium toothpaste on the tooth enamel surface in in situ conditions. Methods: The research material comprised 20 healthy premolars extracted for orthodontic reasons from children aged 12–14 years. An in situ model was prepared by placing the samples of artificially decalcified enamel on the buccal surfaces of first molars in 6 oral environments. Samples were exposed for the period of 3 or 6 months to one of the two experimental toothpastes: 1) supplemented with Ca2+ and P03 ions (“HAP”); 2) supplemented with Ca2+, P03 and Sr2+ ions (“HAP+Sr”). Quantitative X–ray EDS microanalysis was performed to examine the contents of Ca, P, Mg, Na, K, Cl and Sr in the enamel surface. Selected oral cavity parameters, ie saliva pH, saliva flow rate and osmolarity, saliva contents of Ca, P, Na, K, F, Sr, total protein and albumin saliva level at baseline, during the experiment and after its completion, were analysed with standard biochemical methods. Results: After 3 months there was significant increase of Ca and P content in the enamel surface in “HAP” (p<0.001 and p<0.01, respectively) and “HAP+Sr” group (p<0.05 both), and of Sr contents in “HAP+Sr” group (p<0.001), as compared to the control enamel evaluated immediately after the damage. After 6 months no significant differences in the contents of the analysed elements could be detected. None of the experimental toothpastes changed the values of the analysed saliva parameters beyond the physiological range. Conclusion: Introduction of calcium, phosphorus and strontium ions to the oral cavity environment does not significantly change this environment, though it increases the contents of these elements in the enamel.