Biocompatibility of biphasic α,β-tricalcium phosphate ceramics in vitro

The biocompatibility of biphasic α,β-tricalcium phosphate ceramics, obtained by annealing a compact preform based on β-tricalcium phosphate powder, was studied in vitro. It was found that within 10–30 days the adhesion of primary dental pulp stem cells located on the surface of biphasic α,β-tricalcium phosphate ceramics is suppressed. Decrease of the cell number on the surface of biphasic α,β-tricalcium phosphate ceramics, most likely, can be associated with both the pH level (acidic) as a result of hydrolysis of the more soluble phase of α-tricalcium phosphate and with the nature of surface that changes as a result of the formation and growth of hydroxyapatite crystals.

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In vitro tests of biphasic α,β-tricalcium phosphate ceramics enriched with 65% of α-Ca₃(PO4)² modification were carried out.

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Surface morphology of α,β-tricalcium phosphate ceramics gradually changed during in vitro tests for 30 days.

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Sharp edges of hydroxyapatite plate crystallites formed at the surface of ceramics suppressed the cell activity.

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Acidification near the surface of ceramics containing biodegradable α-tricalcium phosphate suppressed the cell activity.

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Acidifying α-tricalcium phosphate is a perspective phase of ceramic composites in combination with alkalinizing phases.

Colloidal forming of macroporous calcium pyrophosphate bioceramics in 3D-printed molds

A technique for colloidal forming of Ca₂P₂O₇ macroporous bioceramics, based on low-pressure injection molding (LPIM) of a glycerol-water slip containing Ca₂P₂O₇ and Ca(Н₂PO₄)₂ into a plastic mold fabricated via FDM 3D-printing, was proposed. Chemical reaction between the solid phases of the water containing slip - Ca₂P₂O₇ and Ca(Н₂PO₄)₂, resulting in brushite (CaHPO₄·2H₂O) formation, led to consolidation of the casting and preserved its complex architecture in the course of mold burning-out. Macroporous ceramics of Kelvin structure (70% macropores with the sizes from 2 up to 4 mm), based on a pre-defined composition with 10 wt% Ca(PO₃)₂ and sintered in liquid-phase regime, demonstrated a compressive strength of 1.4 ± 0.1 MPa at a density of 22 ± 2%. In vitro tests on bioactivity in SBF solution, as well as on resorption of the ceramics in model solution of citric acid, were carried out.

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A new method of calcium phosphate materials fabrication by using colloidal forming and 3-D printing was proposed.

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In the course of sintering, incongruent evaporation of the calcium-metaphosphate-enriched melt occurs.

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The maximum strength were observed for the ceramics containing 10 wt% Ca(PO₃)₂, sintered at 1000°C for 1 hour.

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Hydroxyapatite nuclei after 24 h and layer after 120 h formation on the materials surface is observed.