Ceramic materials in Na2O-CaO-P2O5 system were obtained by firing cement-salt stone made from pastes based on powder mixtures including calcium citrate tetrahydrate Ca3(C6H5O7)2∙4H2O, monocalcium phosphate monohydrate (MCPM) Ca(H2PO4)2∙H2O and/or sodium dihydrogen phosphate NaH2PO4. The phase composition of the obtained samples of cement-salt stone after adding water, hardening and drying included brushite CaHPO4∙2H2O, monetite CaHPO4 and also unreacted Ca3(C6H5O7)2∙4H2O, Ca(H2PO4)2∙H2O and/or NaH2PO4. The phase composition of ceramics in Na2O-CaO-P2O5 system obtained by firing cement-salt stone was formed due to thermal conversion of hydrated salt and heterophase reactions between components presented in samples during firing. The phase composition of ceramic samples based on powder mixture of Ca3(C6H5O7)2∙4H2O and Ca(H2PO4)2∙H2O after firing at 900 °C included β-calcium pyrophosphate (CPP) β-Ca2P2O7. The phase composition of ceramic samples based on powder mixture of Ca3(C6H5O7)2∙4H2O, and NaH2PO4 after firing at 900 °C included β-sodium rhenanite β-CaNaPO4. The phase composition of ceramic samples based on powder mixture of Ca3(C6H5O7)2∙4H2O, Ca(H2PO4)2∙H2O and NaH2PO4 after firing at 900 °C included β-Ca2P2O7, β-CaNaPO4, double calcium-sodium pyrophosphate Na2CaP2O7, and Na-substituted tricalcium phosphate Сa10Na(PO4)7. Obtained ceramic materials in Na2O-CaO-P2O5 system including biocompatible and biodegradable phases could be important for treatments of bone tissue defects by means of approaches of regenerative medicine.

— β-Tricalcium phosphate (β-Ca 3 (PO 4 ) 2 ) based ceramics with a relative density of 20–21%, grain size from 200 to 600 nm, and compressive strength from 1.6 to 1.8 MPa have been produced by 1000°C firing of cement stone prepared from a powder mixture having a Ca/P molar ratio of 1.5 and consisting of hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ), calcium citrate tetrahydrate (Ca 3 (C 6 H 5 O 7 ) 2 ·4H 2 O), and calcium dihydrogen phosphate monohydrate (Ca(H 2 PO 4 ) 2 ·H 2 O). The mixing liquid used to initiate chemical binding reaction in the powder mixture was distilled water. The phase composition of the cement stone included brushite (CaHPO 4 ·2H 2 O) and unreacted starting materials. The presence of platelike calcium pyrophosphate (Ca 2 P 2 O 7 ) particles, formed from platelike brushite (CaHPO 4 ·2H 2 O) particles, impeded densification of the ceramics during firing and ensured the formation of an ultraporous structure. The submicron-grained microstructure and phase composition of the β-Ca 3 (PO 4 ) 2 -based ceramics resulted mainly from heterophase interactions between the products of thermal decomposition of cement stone components. Offering sufficient strength, biocompatible and bioresorbable ultraporous submicron-grained β-Ca 3 (PO 4 ) 2 -based ceramics can be recommended for use in regenerative medicine for bone tissue defect repair.

Low-temperature ceramics based on magnesium calcium phosphate cement are a promising resorbable material for bone tissue restoration with the possibility of functionalization. The replacement of the magnesium Mg2+ ion with a calcium Ca2+ ion at the stage of preparation of the precursor leads to the production of multiphase ceramics containing phases of brushite, monetite, and newberyite, with different dissolution rates. Multiphase ceramics leads to volumetric resorption with preservation of their geometric shape, which was confirmed by the results of an evaluation of the output of magnesium Mg2+ and calcium Ca2+ ions into the contact solution of the ceramics and the X-ray density of ceramic samples during subcutaneous implantation. The combined introduction of sodium pyrophosphate decahydrate and citric acid monohydrate as setting inhibitors neutralizes their insignificant negative effect on the physico-chemical properties of ceramics (strength, pH, porosity), determining the optimal composition. In vivo experiments with setting inhibitors in the composition of ceramics showed a different biological response, affecting the rate of resorption on par with magnesium ions. Preliminary data on biocompatibility and solubility determined magnesium-calcium phosphate ceramics containing additives that regulate setting to be a potential material for bone tissue restoration and a vector for further research, including in orthotopic implantation models.

Interest in calcium phosphate cements as materials for the restoration and treatment of bone tissue defects is still high. Despite commercialization and use in the clinic, the calcium phosphate cements have great potential for development. Existing approaches to the production of calcium phosphate cements as drugs are analyzed. A description of the pathogenesis of the main diseases of bone tissue (trauma, osteomyelitis, osteoporosis and tumor) and effective common treatment strategies are presented in the review. An analysis of the modern understanding of the complex action of the cement matrix and the additives and drugs distributed in it in relation to the successful treatment of bone defects is given. The mechanisms of biological action of functional substances determine the effectiveness of use in certain clinical cases. An important direction of using calcium phosphate cements as a carrier of functional substances is the volumetric incorporation of anti-inflammatory, antitumor, antiresorptive and osteogenic functional substances. The main functionalization requirement for carrier materials is prolonged elution. Various release factors related to the matrix, functional substances and elution conditions are considered in the work. It is shown that cements are a complex system. Changing one of the many initial parameters in a wide range changes the final characteristics of the matrix and, accordingly, the kinetics. The main approaches to the effective functionalization of calcium phosphate cements are considered in the review.

Composite powders were synthesized from the water solutions of sodium silicate and different calcium salts (nitrate, chloride, and acetate) at a Ca/Si molar ratio of 1.0. According to the XRD data, all the synthesized powders included hydrated calcium silicate Ca1,5SiO3,5·xH2O (Ca/Si molar ratio = 1.5) and calcium carbonate CaCO3 (Ca/Si molar ratio = ∞). The presence of H2SiO3 or SiO2·xH2O in the synthesized powders was assumed to be due to the difference between the Ca/Si molar ratio of 1.0 specified by the synthesis protocol and the molar ratio of the detected products. Reaction by-products (sodium nitrate NaNO3, sodium chloride NaCl, and sodium acetate NaCH3COO) were also found in the synthesized powders after filtration and drying. According to the XRD data phase composition of all powders after washing four times consisted of the quasi-amorphous phase and calcium carbonate in the form of calcite. Calcium carbonate in the form of aragonite was detected in powders synthesized from calcium chloride CaCl2 and calcium nitrate Ca(NO3)2 before and after washing. Synthesized powders containing reaction by-products and washed powders were used for the preparation of ceramics at 900, 1000, and 1100 °C. The phase composition of the ceramic samples prepared from the washed powders and powder containing NaCl after firing at 900 and 1000 °C consisted of β-wollastonite β-CaSiO3, and, after firing at 1100 °C, consisted of both β-wollastonite β-CaSiO3 and pseudo-wollastonite α-CaSiO3. The phase composition of the ceramic samples prepared from powders containing sodium nitrate NaNO3 and sodium acetate NaCH3COO after firing at 900, 1000, and 1100 °C consisted of calcium sodium silicates, i.e., Na2Ca2Si3O9 (combeite) and Na2Ca3Si2O8. Synthesized and washed composite powders can be used for the preparation of biocompatible materials, in the technology of construction materials, and as components of lunar soil simulants.

β-Tricalcium phosphate (β-Ca3(PO4)2) based ceramics with a relative density of 20–21

Ceramics with post-firing (600 – 900°C) phase composition represented by calcium sulfate anhydrite CaSO 4 and sodium calcium sulfates (Na 0.8 Ca 0.1 ) 2 SO 4 and Na 6 Ca(SO 4 ) 4 was obtained from a powder mixture of sodium sulfate Na 2 SO 4 and calcium sulfate dihydrate CaSO 4 ∙ 2H 2 O with molar ratio CaSO 4 ∙ 2H 2 O/Na 2 SO 4 = 1. The phase composition of the powder mixture after homogenization (in acetone) in a planetary mill included, in addition to the initial salts, hydrated sodium calcium sulfate Na 4 Ca(SO 4 ) 3 ∙ 2H 2 O. On soaking in water for 5 and 60 min the weight loss of the ceramic sample fired at 700°C was equal to 15 and 75%, respectively. Na 2 O–CaO–SO 3 ceramics in the form of granules or complex structures obtained by means of 3D printing can be used as a removable (soluble or leachable) porogen and (or) a prototype of a porous space with specified architecture to obtain porous polymeric or inorganic materials.

A mixture of abramis brama (freshwater bream), carassius carassius (crucian carp), and sander lucioperca (pike perch) scales was used for the preparation of fish scale powder containing constituents of organic and inorganic nature. The mixture of the mentioned fish scales was washed, dried, and ground for the preparation of fish scale powder. Vibration sieving was used to prepare fish scale powder enriched with inorganic components. According to thermal analysis data, this fish scale powder enriched with inorganic components included about 36.5 wt.% components removed when heating, primarily those of organic nature, and 63.5 wt.% mineral components. Inorganic powders consisting of hydroxyapatite and magnesium whitlockite were obtained via heat treatment of this fish scale powder at 800–1000 °C. Particles of these inorganic powders consisted of sintered grains with dimensions less than 100 nm after heat treatment at 800 °C, less than 200 nm after heat treatment at 900 °C, and 100–1000 nm after heat treatment at 1000 °C. Fish scale powder enriched with inorganic components as well as heat-treated inorganic powders consisting of hydroxyapatite and magnesium whitlockite can be recommended for the production of different materials, such as ceramics or composites.

Ceramic samples based on β-calcium pyrophosphate β-Ca2P2O7 were prepared from powders of γ-calcium pyrophosphate γ-Ca2P2O7 with preset molar ratios Ca/P = 1, 0.975 and 0.95 using firing at 900, 1000, and 1100 °C. Calcium lactate pentahydrate Ca(C3H5O3)2⋅5H2O and monocalcium phosphate monohydrate Ca(H2PO4)2⋅H2O were treated in an aqua medium in mechanical activation conditions to prepare powder mixtures with preset molar ratios Ca/P containing calcium hydrophosphates with Ca/P = 1 (precursors of calcium pyrophosphate Ca2P2O7). These powder mixtures containing calcium hydrophosphates with Ca/P = 1 and non-reacted starting salts were heat-treated at 600 °C after drying and disaggregation in acetone. Phase composition of all powder mixtures after heat treatment at 600 °C was presented by γ-calcium pyrophosphate γ-Ca2P2O7 according to the XRD data. The addition of more excess of monocalcium phosphate monohydrate Ca(H2PO4)2·H2O (with appropriate molar ratio of Ca/P = 1) to the mixture of starting components resulted in lower dimensions of γ-calcium pyrophosphate (γ-Ca2P2O7) individual particles. The grain size of ceramics increased both with the growth in firing temperature and with decreasing molar ratio Ca/P of powder mixtures. Calcium polyphosphate (t melt = 984 °C), formed from monocalcium phosphate monohydrate Ca(H2PO4)2⋅H2O, acted similar to a liquid phase sintering additive. It was confirmed by tests in vitro that prepared ceramic materials with preset molar ratios Ca/P = 1, 0.975, and 0.95 and phase composition presented by β-calcium pyrophosphate β-Ca2P2O7 were biocompatible and could maintain bone cells proliferation.

Ceramics with phase composition after firing in the range of 600 – 900 °C represented by anhydrous calcium sulfate CaSO4, and calcium sodium sulfates (Na0,8Ca0,1)2SO4 and Na6Ca(SO4)4 were obtained from a powder mixture of sodium sulfate Na2SO4 and calcium sulfate dihydrate CaSO42H2O, taken at a molar ratio CaSO42H2O/Na2SO4 = 1. The phase composition of the powder mixture after homogenization in a planetary mill in an acetone medium, in addition to the starting salts, also included hydrated sodium calcium sulfate Na4Ca(SO4)32H2O. When kept in water for 5 and 60 min the mass loss of ceramic sample fired at 700 °C was 15 and 75 % respectively. Ceramics in the Na2O–CaO–SO3 system in the form of granules or complex shapes obtained using 3D printing can be used as a removable (soluble or leachable) porogen and/or a prototype of a porous space with a given architecture when creating porous polymer or inorganic materials.

Biocompatibility of ceramic materials in Ca2P2O7-Ca(PO3)2 system was investigated using different methods, including in vitro and in vivo tests. Ceramic materials in the Ca2P2O7-Ca(PO3)2 system were obtained by annealing cement-salt stone based on powder mixtures of calcium citrate tet-rahydrate Ca3(C6H5O7)2·4H2O and monocalcium phosphate monohydrate (MCPM) Ca(H2PO4)2·H2O. The phase composition of cement-salt stone included brushite, monetite as a result of chemical reaction of starting components after adding of water. The presence of citric acid as by-product of chemical reaction, leads to increase the setting time of the cement-salt stone. Highly concentrated aqueous suspensions based on calcium citrate and MCPM powders providing content of calcium polyphosphate Ca(PO3)2 up to 20 wt % in ceramics were used for designing bioresorbable materials. The presence of an excess of monocalcium phosphate monohydrate makes it possible to reduce the annealing temperature of ceramics, which is associated with the formation of a lower melting phase of Ca(PO3)2. In vivo tests shown that obtained ceramic materials can be recommended for regenerative treatments for bone defects.

Biocompatibility of ceramic materials in CaO-P2O5 system was investigated using different methods, including in vitro and in vivo tests. Ceramics based on calcium pyrophosphate Ca2P2O7 were obtained by annealing cement-salt stone from highly concentrated hardening suspensions (HCHS). Cement-salt stone was prepared using powder mixtures of calcium citrate tetrahydrate Ca3(C6H5O7)2·4H2O and monocalcium phosphate monohydrate (MCPM) Ca(H2PO4)2·H2O. These salts were mixed with each other in such a way that calcium pyrophosphate and calcium polyphosphate were present in the final ceramic product in the following weight ratios: Ca(PO3)2/Ca2P2O7 = 0/100; 5/95; 10/90 and 20/80. Distilled water was added to a homogenized powder mixtures of Ca3(C6H5O7)2·4H2O and Ca(H2PO4)2·H2O by a water/solid ratio of 0,5 by weight. The obtained suspensions were shaped using silicon molds and left to dry in air for a week. The phase composition of the obtained samples of cement-salt stone was represented by brushite CaHPO4·2H2O, monetite CaHPO4, calcium citrate tetrahydrate Ca3(C6H5O7)2·4H2O and monocalcium phosphate monohydrate Ca(H2PO4)2·H2O. According to the XRD data, the phase composition of ceramic materials after annealing in the temperature range of 800-1000 0C was mainly represented by the β-Ca2P2O7 phase. In vivo tests shown that obtained ceramic materials can be recommended for regenerative treatments for bone defects.

Local drug delivery systems are an effective approach in the treatment of purulent–septic inflammation of bone tissue. Chemically bonded multiphase ceramics based on calcium-deficient carbonate-substituted hydroxyapatite combine resorbability, osteoconductivity, and the possibility of volumetric incorporation of antibiotics. Macroporosity is regulated by the concentration of polyethylene glycol granules introduced into the initial powder composition, followed by their extraction. The selected conditions for the consolidation of the ceramic matrix and the extraction of PEG granules retain the activity of vancomycin, which is confirmed by the results of microbiological studies. The concentration of vancomycin and the porosity affect the local concentration and release of the antibiotic. The incorporation method provides a prolonged release of the antibiotic for up to 31 days. In vivo experiments with bone implantation have shown that chemically bound macroporous ceramics with incorporated vancomycin are a therapeutically effective carrier of the substance during the healing of bone defects in conditions of surrounding purulent–septic inflammation, and can be considered as a carrier for local antibacterial therapy, at the site of implantation.

Ceramics based on rhenanite CaNaPO4 with density of 0.94 g/cm3 and compressive strength of 10.3 MPa was obtained via firing at 900 °C of composite cement-salt stone prepared from a hardening powder mixture of calcium citrate tetrahydrate Ca3(C6H5O7)2∙4H2O and sodium dihydrogen phosphate NaH2PO4. The phase composition of the obtained samples of cement–salt stone was represented by monetite CaHPO4, unreacted sodium dihydrogen phosphate and calcium citrate tetrahydrate. According to the XRD data, the phase composition of the ceramic samples after annealing in the temperature range of 500–700 °C was mainly represented by the β-CaNaPO4 phase. It was found that after an annealing at temperature of 900 °C, the phase composition of ceramics was presented with the only phase of β-CaNaPO4. It was demonstrated that an increase in the annealing temperature led to an increase in the grain size from 1 μm after annealing at 500 °C to 5 μm after annealing at 900 °C. Obtained ceramic material based on CaNaPO4 could be important for regenerative treatments of bone tissue defects.

Ceramics consisting of anhydrous calcium sulfate, CaSO4, after firing in the range 800–1000°C have been prepared from calcium sulfate dihydrate (CaSO4⋅2H2O) powder synthesized using aqueous 1 M calcium nitrate (Ca(NO3)2) and ammonium sulfate ((NH4)2SO4) solutions. In the preparation of the powder, the precipitate was washed four times with distilled water to remove ammonium nitrate, NH4NO3, a reaction by-product and, after drying, the powder was disaggregated in acetone. The synthesized CaSO4⋅2H2O powder particles had an elongated prismatic shape both before and after disaggregation. After firing at 800, 900, and 1000°C, the microstructure of the ceramics based on the synthesized CaSO4⋅2H2O powder free of reaction by-products contained sintered elongated polycrystalline structures, confirming that the ceramics inherited the microstructure of the starting powder. Ceramics consisting of anhydrous calcium sulfate, CaSO4, can be recommended for the fabrication of implants for bone tissue defect repair by regenerative medicine methods because they are biocompatible and bioresorbable.

— Ceramics consisting of anhydrous calcium sulfate, CaSO 4 , after firing in the range 800–1000°C have been prepared from calcium sulfate dihydrate (CaSO 4 ⋅2H 2 O) powder synthesized using aqueous 1 M calcium nitrate (Ca(NO 3 ) 2 ) and ammonium sulfate ((NH 4 ) 2 SO 4 ) solutions. In the preparation of the powder, the precipitate was washed four times with distilled water to remove ammonium nitrate, NH 4 NO 3 , a reaction by-product and, after drying, the powder was disaggregated in acetone. The synthesized CaSO 4 ⋅2H 2 O powder particles had an elongated prismatic shape both before and after disaggregation. After firing at 800, 900, and 1000°C, the microstructure of the ceramics based on the synthesized CaSO 4 ⋅2H 2 O powder free of reaction by-products contained sintered elongated polycrystalline structures, confirming that the ceramics inherited the microstructure of the starting powder. Ceramics consisting of anhydrous calcium sulfate, CaSO 4 , can be recommended for the fabrication of implants for bone tissue defect repair by regenerative medicine methods because they are biocompatible and bioresorbable.

Ceramics consisting of anhydrous calcium sulfate, CaSO4, after firing in the range 800-1000 degrees C have been prepared from calcium sulfate dihydrate (CaSO4 center dot 2H(2)O) powder synthesized using aqueous 1 M calcium nitrate (Ca(NO3)(2)) and ammonium sulfate ((NH4)(2)SO4) solutions. In the preparation of the powder, the precipitate was washed four times with distilled water to remove ammonium nitrate, NH4NO3, a reaction by-product and, after drying, the powder was disaggregated in acetone. The synthesized CaSO4 center dot 2H(2)O powder particles had an elongated prismatic shape both before and after disaggregation. After firing at 800, 900, and 1000 degrees C, the microstructure of the ceramics based on the synthesized CaSO4 center dot 2H(2)O powder free of reaction by-products contained sintered elongated polycrystalline structures, confirming that the ceramics inherited the microstructure of the starting powder. Ceramics consisting of anhydrous calcium sulfate, CaSO4, can be recommended for the fabrication of implants for bone tissue defect repair by regenerative medicine methods because they are biocompatible and bioresorbable.