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Brushite coatings were obtained on titanium by the method of electrochemical deposition from Ca(NO3)2/NH4H2PO4 electrolyte at Ca/P = 1.67, pH 4, and a constant voltage of 15 V or a current density of 20 mA/cm2 for 20 min. In a medium of 0.01–0.10% polyvinyl alcohol at a constant voltage of 15 V, single-phase brushite or monetite coatings are deposited. The addition of 0.01–0.10% polyvinyl alcohol to the electrolyte during deposition at a constant current density of 20 mA/cm2 leads to the formation of composite calcium phosphate coatings containing brushite, calcium hydroxide, and calcium phosphate of the apatite structure. The bioactivity of calcium phosphate coatings was confirmed by the formation of apatites during their soaking in the Simulated Body Fluid (SBF). Amorphized apatite that formed on brushite coatings during soaking for 2 weeks in SBF crystallizes into β-tricalcium phosphate after heat treatment. The apatite that formed on the composite coating in the SBF crystallizes into a composition of hydroxyapatite and β-tricalcium phosphate. The resulting bioactive calcium phosphate coatings can be used as biocoatings to enhance osseointegration of titanium implants. [ABSTRACT FROM AUTHOR]

Powders of calcium pyrophosphate Ca2P2O7 of γ- and β-modifications have been obtained using the thermal conversion of brushite CaHPO4⋅2H2O synthesized from phosphoric acid H3PO4 and calcium carbonate CaCO3 at a molar ratio P/Ca = 1.1. The resulting powders can be used to create various functional materials, including biocompatible and bioresorbable materials for the treatment of bone defects. [ABSTRACT FROM AUTHOR]

Calcium phosphate powder were synthesized from aqueous solutions of calcium lactate Ca(C3H5O3)2 and ammonium hydrophosphate (NH4)2HPO4 at a Ca/P = 1 molar ratio. According to the XRD data, the phase composition of as-synthesized powder consisted of brushite CaHPO4 ⋅ 2H2O and hydroxyapatite Ca10(PO4)6(OH)2. After heat treatment at 350–600°C, the powder was colored dark brown owing to the destruction of the by-product of the reaction. The composition of the powder heat-treated at 350°C included monetite CaHPO4 and hydroxyapatite Ca10(PO4)6(OH)2, and the powder heat-treated at 600°C consists of hydroxyapatite Ca10(PO4)6(OH)2 and γ-calcium pyrophosphate γ-Ca2P2O7. The phase composition of ceramic obtained from the synthesized powder after sintering at 1100°C consisted of β-calcium pyrophosphate β-Ca2P2O7 and β‑tricalcium phosphate β-Ca3(PO4)2. The colored after the heat treatment in a range of 350–600°C powders can be used as a starting for the molding of porous biocompatible calcium phosphate composite materials with the given geometry of the porous space by stereolithographic printing. The synthesized powder can be recommended for the development of biocompatible and biodegradable both ceramic composite materials and composites with polymer or inorganic matrix for bone implants. [ABSTRACT FROM AUTHOR]

Calcium phosphate ceramics, with the phase composition represented by β-calcium pyrophosphate β-Ca2P2O7, was obtained from a powder mixture of calcium hydroxyapatite Ca10(PO4)6(OH)2, monocalcium phosphate monohydrate Ca(H2PO4)2 · H2O, and sodium hydrogen phosphate Na2HPO4. The powder mixture was preliminarily homogenized in acetone using a planetary mill. This treatment resulted in the chemical reaction between the starting components to form monetite, calcium hydrogen phosphate CaHPO4 (precursor of calcium pyrophosphate Ca2P2O7). According to the XRD data, sodium hydrogen phosphate Na2HPO4 when present in an amount of 5 wt % in the starting mixture had no effect on the phase composition of the powder after homogenization and of the ceramics after annealing. Sodium pyrophosphate Na4P2O7 formed from sodium hydrogen phosphate Na2HPO4 as a result of thermal conversion had a significant effect on sintering mechanism and the microstructure of the ceramics. A ceramics with a low sintering temperature based on β-calcium pyrophosphate β-Ca2P2O7 was obtained for the first time from a powder system, upon preparation of which under mechanical activation conditions homogenization of components and synthesis of the main crystal phase precursor were combined. [ABSTRACT FROM AUTHOR]

Calcium phosphate ceramics in the Ca2P2O7–Ca(PO3)2 system was obtained by annealing of hardened samples formed from highly loaded suspensions (HLS). HLSs included water and a homogenized powder mixture of calcium citrate tetrahydrate Ca3(C6H5O7)2 ⋅ 4H2O and monocalcium phosphate monohydrate Ca(H2PO4)2 ⋅ H2O. The latter was taken in the amount providing the molar ratio of Ca/P = 1 in the powder mixture, as well as at a molar ratio of Ca/P < 1 so that the excess of monocalcium phosphate monohydrate Ca(H2PO4)2 ⋅ H2O provided the formation of the calcium polyphosphate Ca(PO3)2 phase upon annealing. The samples were molded by extrusion of the HLS through a die with a diameter of 2 mm by sandwiching powder cords. After hardening and drying, the phase composition of all obtained samples included brushite CaHPO4 ⋅ 2H2O, monetite CaHPO4, monocalcium phosphate monohydrate Ca(H2PO4)2 · H2O, and octacalcium phosphate Ca8(HPO4)2(PO4)4H2O. According to the XRD data, the phase composition of all ceramic samples after annealing in a range of 800–1000°C included calcium β-pyrophosphate β-Ca2P2O7, and a ceramic sample obtained from a powder mixture with the highest excess of monocalcium phosphate monohydrate Ca(H2PO4)2 · H2O additionally included tromelite Ca4P6O19. Hardening HLSs containing water and a homogenized powder mixture of calcium citrate Ca3(C6H5O7)2 · 4H2O and monocalcium phosphate monohydrate Ca(H2PO4)2 · H2O can be used for layer-by-layer extrusion molding. The resulting calcium phosphate ceramics with lowered sintering temperature can be used for the design of a resorbable matrices of tissue engineering constructs. [ABSTRACT FROM AUTHOR]

Absract: —On the basis of calcium phosphate compositions with a 30% polyvinyl alcohol content, three-dimensional mockups have been obtained using 3D bioprinting. It is shown that at a content of 7–14% of the polymer, calcium phosphate compositions are well extruded and exhibit the strength after hardening up to 4 MPa. Heating compositions Ca10(PO4)6 (OH)2/α-Ca3(PO4)2 up to 900°С in the presence of CaHPO4 promotes phase transformations mainly into β-Ca3(PO4)2 and β-Ca2P2O7. [ABSTRACT FROM AUTHOR]