The influence of precursor concentration, pressure, temperature and time of hydrothermal synthesis on the development of calcium hydroxyapatite structure has been analyzed. The obtained results show that it is possible to adjust the conditions of hydrothermal synthesis from solutions of relatively high concentrations to obtain calcium hydroxyapatite nanopowders of well-defined structure. The relationship between the synthesis and the lattice parameters, as well as the crystallite size and the microstructure of synthesized hydroxyapatite has been established. The synthesized powders are preferentially carbonated hydroxyapatite of the B type in the form of agglomerates that accommodate two-modal size pores of 1.5-10 and 50-200 nm. The structure of calcium hydroxyapatite particles consists of crystallites 8-22 nm in size, bound within prime particles, which size is between 10 and 63 nm, that in turn form bigger agglomerates 200 nm in size, which further cluster building up agglomerates 5-20 microm in size.

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The aim of this study was to synthesize and characterize new superplastic endodontic mixtures (named as ALBO‐MPSA) with strongly accelerated hydration rate. Two different ALBO‐MPSA mixtures were prepared using combination of hydrothermal and high‐temperature self‐propagating method. Phase analysis of the mixtures, before and after hydration, was carried out by X‐ray diffraction (XRD), while morphological analysis was performed by scanning electron microscopy (SEM). Investigations of mechanical properties showed that new superplastic, quick‐bonding endodontic mixtures with good mechanical properties were obtained (compressive strength after 28 days aging was from 35.7 ± 0.5 and 37.4 ± 0.5 MPa). The final phase compositions after hydration of the mixtures were determined on the base of XRD data, assumed mechanism of hydration and rational chemical analysis. The constitutive phases were tobermorite, portlandite, and amorphous Ca(OH)2, ettringite and amorphous like ettringite phase, gypsum, hydroxyapatite and barite.