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 discuss therapy possibilities in the management of molar incisor hypomineralization. Molar incisor hypomineralization (MIH) is defined as hypomineralization of one or more first permanent molars frequently affecting incisors. Etiology of MIH is not fully clarified and numerous etiological factors have been cited. Hypomineralized molars are more prone to caries, cause severe restorative problems and are frequently extracted due to serious damage and caries complications. Incisors can present demarcated enamel opacities, while enamel breakdown is uncommon. Clinically, affected molars can be sensitive to thermal and chemical irritations even when there is no enamel breakdown. Molars can be sensitive to mechanical irritations making even regular tooth brushing painful. Specific problems related to the treatment of these teeth are sensitivity and occlusion in molars and aesthetics in incisors. Considering the fact that permanent first molars with severe defects and incisors demand complex and multidisciplinary treatment they present serious problem for the patient as well as for the dentist

Mineral trioxide aggregate (MTA) is a material with broad indications in endodontics. Currently, this material is used for pulp capping, pulpotomy, as apical barrier in teeth with necrotic pulp and open apex, and in the treatment of various root canal perforations. By comparing the biological response of pulp tissue capped with calcium hydroxide and MTA, the superiority of MTA has been indicated. The bridge of hard tissue formed under MTA prevented the irritation of pulp. Histological studies of pulpotomy in dog teeth have shown after 120 days a hard tissue without necrosis formed under MTA. MTA is also the material of choice for retrograde root canal obturation and lateral perforation. Meta analysis of published papers on MTA in recent years indicated the great clinical success of this material which ensured a good canal seal and superior biocompatibility. It is the only material for retrograde root canal obturation that encourages tissue regeneration. Studies have also shown that MTA has inductive and conductive properties for hard tissue as well as the ability to release ions in a liquid medium. The main disadvantage of MTA is related to its color, the presence of iron and mangan ions, the difficulties in maintaining the characteristics of material during time, absence of solvent for this material and the difficulty for its removal after crosslinking

Cytotoxicity testing, as a standard assay for toxicity of dental materials, is useful for initial biocompatibility evaluations. In vitro test of calcium hydroxyapatite (CHA) with established laboratory cell line showed multiple partitions of cells proving good biocompatibility properties of this new material. Further research should be directed towards simulation of in vivo conditions and animal experimentation to obtain sufficient data before its clinical application in humans.