Experimental study (in vitro) of intact premolars extracted considering the orthodontic indications in patients aged from 11 to 13 years old was performed to attest the structural state of calcium hydroxiappatite in the dentine using the electronmicroscopic and roentgenographiic methods. It was found out that the structural type of calcium hydroxiappatite determined through the peaks location in the roentgenograms appeared to be of hexaganal type. The elemental analysis made using the EDXA spectrometer placed on the electron microscope showed that the juvenile crown dentine in the foils contained the constituents of calcium hydroxiappatite (Ca, P, O, C ). The electronograms analysis of these sites indicated that the dentine including its mineral constituent is in the amorphic state which points to a low degree of its mineralzation.