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Three-dimensional interconnected porous carbonate apatite (3D-CO 3 Ap) bone grafts facilitate rapid bone replacement because of their structure, which supports cellular infiltration. Existing 3D-CO 3 Ap grafts have demonstrated limited mechanical strength, with a maximum compressive strength of 3 MPa. By fusing polymer-bound CaCO 3 granules, followed by the debinding and compositional transformation of the granules via a dissolution–precipitation reaction, we successfully fabricated 3D-CO 3 Ap grafts that exhibited remarkably enhanced compressive strengths, which were recorded at 14.9 ± 3.7 MPa. The use of spherical granules, which provide more uniform and effective intergranular contacts than cylindrical granules, was key to achieving higher mechanical strength and superior bone formation. 3D-CO 3 Ap developed with spherical granules not only exhibited higher compressive strength, but also enhanced new bone formation compared with those fabricated with cylindrical granules. This study underscores the significance of porous microstructure design in 3D-CO 3 Ap, highlighting its critical role in optimizing both mechanical properties and bone regeneration capabilities. [ABSTRACT FROM AUTHOR]

Carbonate apatite (CAp) coating has been developed as a bioabsorbable corrosion-control coating for biodegradable Mg alloys. Carbonate content in the CAp coatings can be utilized to control the bioabsorbability and corrosion rate of CAp-coated Mg alloys. In this study, the carbonate content in the CAp coatings of pure Mg was varied by NaHCO 3 concentration of the coating solution from 0.25 to 1.0 mol/L, and hydroxyapatite (HAp) was formed without NaHCO 3. The CAp and HAp coatings were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The carbonate content in the apatite coatings formed with 0, 0.25, 0.5 and 1.0 mol/L NaHCO 3 was determined to be 2, 12, 15 and 18 wt%, respectively, from the apatite 002 plane XRD peak position using the existing conversion constant as well as from the coating composition obtained by the XPS analysis. The values of carbonate content obtained by each method were in good accordance, indicating that the carbonate content can be determined simply by XRD measurements. Two types of carbonate group were present in the CAp coatings, CO 3 2− and HCO 3 -, and the relative content of HCO 3 - to CO 3 2− increased with an increase in the carbonate content. [Display omitted] • Variation of carbonate content of CAp coatings of pure Mg with NaHCO 3 concentrations. • Accordance in carbonate content derived from XRD peak position and XPS quantification. • Simple determination of carbon content of CAp coatings by XRD is possible. • Two types of carbonate group in CAp coatings, CO 3 2− and HCO 3 -. [ABSTRACT FROM AUTHOR]

Bioactive glasses are considered biocompatible materials that form a hydroxyapatite-like layer on the surface that allows strong adhesion to soft and hard tissues. This study aims to develop a method to fabricate a borate silicate ceramic biomaterial with a chemical composition of Ca 11 Si 4 B 2 O 22 using sodium metaborate (NaBO 2) as a flux. X-ray diffraction (XRD), scanning electron microscopy energy distribution spectrometer (SEM-EDS), and Fourier transform infrared spectrometer (FTIR) were used to analyze the structure, surface composition and chemical bonding of the bioactive borate silicate. In addition, the pH measurements and biodegradability behavior of the fabricated glass structures were investigated after immersion in simulated body fluid for 2, 7, 14, and 21 days, respectively. The results showed that the glass-ceramic structure, which was transferred from the crystalline phase Ca 11 Si 4 B 2 O 22 to a hydroxyapatite phase after incubation, started on the second day. In addition, the formed hydroxyapatite crystals developed due to the prolonged immersion time, reflecting biodegradable behavior. The antimicrobial activity of the prepared ceramic showed high inhibitory activity against Enterococcus faecalis and Streptococcus mutans. [ABSTRACT FROM AUTHOR]

Carbonate apatite (CO 3 Ap) artificial bone is fabricated in an aqueous solution using calcium carbonate as a precursor. CO 3 Ap has attracted attention because it demonstrates high osteoconductivity and can replace a damaged bone based on the bone remodeling process. This study aims to compare vaterite and calcite, which are metastable and stable polymorphs of calcium carbonate, respectively, as precursors. When the vaterite granules, which have higher solubility and consist of smaller crystals than calcite, prepared from calcium oxide granules were immersed in disodium hydrogen phosphate solution, the compositional transformation to CO 3 Ap was quicker than that of calcite. Based on the investigations on rabbit femurs, it was observed that the remodeling of CO 3 Ap to a new bone was faster when vaterite was used as a precursor compared to when calcite was used as a precursor. It is concluded that vaterite can be a better precursor than calcite for CO 3 Ap artificial bone fabrication. [ABSTRACT FROM AUTHOR]

Granular-shaped carbonate apatite (CO 3 Ap) bone substitute has demonstrated good clinical results, especially in the bone augmentation procedure, because it has high osteoconductivity and can be replaced by a new bone. This study aimed to evaluate the potential usefulness of CO 3 Ap bone substitute for alveolar ridge preservation of beagle dogs during the 9-week follow-up period after surgery. Reconstruction of extraction sockets with CO 3 Ap granules (CO 3 Ap group) allowed approximately 1.0 mm higher alveolar bone height than that with a blood clot (control group) at 4 and 9 weeks after surgery. Additionally, the measured area at the buccal aspect of the alveolar bone in the CO 3 Ap group was approximately 2 mm2 larger than that in the control group at 4 and 9 weeks after surgery. Continuity from the buccal side to palatal side of the alveolar bone was restored, maintaining its contour at 4 weeks after surgery. The amount of bony tissue, especially the amount of mature bone, in the alveolar part was statistically larger than that of control group at 9 weeks after surgery even though complete replacement of CO 3 Ap granules with new bone was not observed within 9 weeks. In conclusion, CO 3 Ap granules have good potential for alveolar ridge preservation. [ABSTRACT FROM AUTHOR]

Carbonate apatite (CO 3 Ap) artificial bone has attracted much attention due to its high osteoconductivity and replacement to bone. CO 3 Ap is an inorganic component of bone, and has been fabricated by compositional transformation through a dissolution–precipitation reaction in Na 2 HPO 4 solution using calcium carbonate as a precursor. In this study, the effects of the CO 3 2− concentration in the Na 2 HPO 4 solution on the CO 3 Ap fabrication reaction and the properties of the fabricated CO 3 Ap were investigated. The rate of the compositional transformation became faster, and more CO 3 containing CO 3 Ap was fabricated using CO 3 2− concentrated in Na 2 HPO 4 solution. The crystal shape of CO 3 Ap changed from scale-like to hexagonal crystals. In addition, the crystallite size increased with increasing CO 3 2− concentration in the Na 2 HPO 4 solution. These changes lead to larger pores (≥0.02 μm) and decreased number of small pores (<0.02 μm) according to the CO 3 content in CO 3 Ap, even though the total pore volume remained the same. These findings indicate that the CO 3 2− concentration in Na 2 HPO 4 solution is an important factor for the CO 3 Ap fabrication reaction and affects the properties of the fabricated CO 3 Ap. [ABSTRACT FROM AUTHOR]

Interconnected porous carbonate apatite (CO 3 Ap) blocks that emulate cancellous bone have potential as an alternative to autografts. The present study aimed to evaluate the feasibility of fabricating a block via a stepwise compositional transformation to CO 3 Ap through dissolution-precipitation reactions of an interconnected porous calcium sulfate dihydrate (CSD) block, which was obtained by the setting reaction of calcium sulfate hemihydrate (CSH) granules. Exposure of the CSH granules to water resulted in a setting reaction. However, the gaps between the granules were clogged, preventing the fabrication of interconnected porous structures. Removing the water in the gaps using filter paper was beneficial in avoiding gap clogging and in fabricating interconnected porous CSD blocks. Although the CSD blocks transformed into CaCO 3 blocks, which maintained the interconnected porous structure through a dissolution-precipitation reaction in a Na 2 CO 3 solution, their mechanical strength was quite low (diametral tensile strength: DTS = 75 kPa). In contrast, a CaCO 3 block with a much greater mechanical strength (DTS = 0.98 MPa) was fabricated when a calcium sulfate anhydrous block made via the heat treatment of the CSD block was used as a precursor. The CaCO 3 block transformed into a CO 3 Ap block (DTS = 2.1 MPa), maintaining the interconnected porous structure through a dissolution-precipitation reaction when immersed in a Na 2 HPO 4 solution. The CO 3 Ap block had macropores initiated by the gaps between the granules and micropores created by the setting reaction of CSH granules and the dissolution-precipitation reactions to form CO 3 Ap. The results obtained in the present study demonstrate that this method is useful for fabricating interconnected porous CO 3 Ap blocks. [ABSTRACT FROM AUTHOR]

In scaffolds used for bone regeneration, osteogenic ability increases and mechanical strength decreases with increasing porosity. To ensure both mechanical strength and osteogenesis, an optimal pore architecture is necessary. Porous glass has high porosity and high mechanical strength, as it is framed with a rigid interconnected silica network and void interspaces in the silica network. In this context, based on the porous structure of glass, we fabricated porous blocks composed of carbonate apatite (CO 3 Ap), which is the major component of human bone mineral, with both high mechanical strength and high porosity. To fabricate the CO 3 Ap blocks, first, calcite-polymethyl methacrylate (PMMA) mixture granules were prepared. Next, the calcite-PMMA granules were allowed to join together in the mold by fusing PMMA, resulting in the formation of porous blocks composed of interconnected calcite-PMMA granules. Next, PMMA was thermally removed and the resultant interconnected calcite granules were partially sintered. Finally, the composition of the interconnected granules was converted from calcite to CO 3 Ap in a dissolution-precipitation reaction. Consequently, CO 3 Ap blocks with a continuous pore architecture were successfully fabricated. The porosity and diametral tensile strength were controllable within the range of 60‒70% and 1.0‒1.5 MPa, respectively, by filling the space between the calcite-PMMA granules. As these values are suitable for clinical use, the porous CO 3 Ap blocks have potential applications as scaffolds for bone regeneration. [ABSTRACT FROM AUTHOR]