Recently it has been shown that very deep lesions, extending through the enamel into the dentin, can still be remineralized when brought into contact with a mineralizing agent. Biodentine is a calcium silicate based dentin substitute recommended to use in dentistry for direct and indirect pulp capping, perforations, apexification and retrograde root filling. The aim of the study was to examine the reaction between Biodentine and dentin comparing chemical composition of both of them in microspectral analysis. The human molars dentinal samples with Biodentine were analyzed by scanning electron microscopy (SEM) and electron probe microanalyser (EDS) with image observation function. Aditionally Raman microscope was used to identify Biodentine/denine interface. The results showed that Biodentine released some of its components into dentin specimens and caused the uptake of Ca and Si in the adjacent dentine. The formation of an interfacial layer at the Biodentine/dentin border was identified as a "Transition Zone". On the basis of performed experiment it can be concluded that Biodentine is an active dental material and microanalytic methods used in the study are suitable to investigate it. The obtained outcomes can open up possibilities for a non-operative approach to deep caries cavities. 2013