Pressureless Sintering and Mechanical and Biological Properties of Fluor‐hydroxyapatite Composites with Zirconia (original) (raw)
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Journal of Biomedical Materials Research Part A, 2005
A fluorine-substituted hydroxyapatite (FHA) and zirconia (ZrO 2) dense composite (50:50 by volume) was fabricated, and its feasibility for hard tissue applications was investigated in terms of its mechanical properties and osteoblast-like cell (MG63) responses in vitro. The incorporation of fluorine into the hydroxyapatite (HA) structure was highly effective in producing a completely dense apatite-ZrO 2 composite through a pressureless sintering route, by preventing the thermal degradation of the apatite and ZrO 2. The resultant FHA-ZrO 2 dense composite had excellent mechanical properties, such as flexural strength (310 MPa), fracture toughness (3.4 MPam 1/2), hardness (10 GPa), and elastic modulus (160 GPa). The flexural strength and fracture toughness of the composite showed a noticeable improvement by a factor of ϳ4 with respect to the pure apatites (HA and FHA). The MG63 cellular responses to the composite were assessed in terms of the cell proliferation (cell number and [ 3 H]-thymidine incorporation) and differentiation (alka-line phosphatase activity, osteocalcin, and collagen production). The cells on the FHA-ZrO 2 composite spread and grew well, and proliferated actively during the culture period. The expression of alkaline phosphatase, osteocalcin, and collagen by the cells on the composite showed a similar trend to that on the pure apatites, although slight downregulations were observed, implying that the FHA-ZrO 2 50:50 composite retains the osteoblastic functionality and traits of the pure HA ceramics to a high degree. This finding, in conjunction with the considerable improvements in mechanical properties, supports the extended use of this composite for hard tissue applications.
Synthesis of Bioactive Hydroxyapatite-Zirconia Toughened Composites for Bone Replacement
Advances in Science and Technology, 2008
Hydroxyapatite (HAp) is a major inorganic component of human hard tissues, such as bones and teeth, and its content determines their microstructures and physical properties. Artificial HAp shows strong biocompatibility and bioactivity and thus it has found broad applications in tissue engineering for replacing damaged hard tissues. The artificial HAp, however, suffers from its intrinsic low mechanical properties, so to meet mechanical requirements, HAp can be incorporated with stiff mineral phases (mullite, zirconia, alumina). The performance and long-term survival of these biomedical devices are also dependent on the presence of bacteria surrounding the implants. In order to reduce the incidence of implant-associated infections, several treatments have been proposed, e.g. introduction of silver or fluoride in the HAp. The objective of this research is the sintering of composites based on calcium phosphate, mainly HAp supported on zirconia, for bone replacement with better microstructural features. In fact the use of zirconia can enhance the mechanical properties of bioceramics. Moreover the introduction of small amounts of silver, which should improve the antibacterial properties, will be taken into consideration since it is expected also to further toughen the whole structure.
Microstructural and Mechanical Properties of Hydroxyapatite–Zirconia Composites
2007
This work focuses on the improvement of the mechanical properties of hydroxyapatite (HA) through the addition of 3 mol% yttria partially stabilized zirconia (PSZ). Enamel-derived HA (EHA) from freshly extracted human teeth and commercial HA (CHA) were chosen as the matrix. The effects of addition up to 10 wt% of PSZ and of sintering temperature (1000°–1300°C) on the density, microhardness, and compression strength were evaluated. For EHA–PSZ composites, the density and mechanical properties were generally enhanced by adding 5 wt% PSZ, especially after sintering at 1200°C, whereas CHA–PSZ composites showed lower strength values at sintering temperatures of 1200° and 1300°C with respect to EHA–PSZ composites. This may be due to the lower stability of CHA–PSZ composites with higher amounts of calcium zirconate formed over 1100°C when compared with EHA–PSZ composites.
Biomedical materials (Bristol, England), 2017
Ceramics and bioceramics, as hydroxyapatite and zirconium, are used in bone tissue engineering. Hydroxyapatite has chemical properties similar to the bone while zirconium offers suitable mechanical properties. The aim of this article is to evaluate the ability to support cellular growth and osteoblastic mineralization of hydroxyapatite-zirconium obtained by a new system based on different low temperatures, as 873°K (HZ600), 923°K (HZ650) and 973°K (HZ700). Hydroxyapatite-zirconia obtained by this new system was examined in terms of thermogravimetric features and X-ray diffractograms. Furthermore, the ability for supporting osteoblast growth and mineralization were analyzed. By x-ray diffraction analysis, we clearly demonstrated that no high-temperature processing was required. Moreover, it is possible to form tetragonal-zirconium at 650°C. Proliferation assay showed that osteoblast growth was not influenced by any of the composite evaluated. Regarding osteogenic marker Col1, a 2 fol...
Hydroxyapatite of natural origin - zirconia composites, preparation and reactions within the system
Processing and Application of Ceramics, 2016
The effect of 5 and 10 vol.% addition of zirconia (3Y-TOSOH) to hydroxyapatite of natural origin was investigated. The hydroxyapatite (HAp) material was extracted from the bovine bones by treatment under hydrothermal conditions with distilled water. The pure HAp and HAp-ZrO2 composites were manufactured by pressureless sintering and hot pressing. The reactions taking place in these systems were observed using the X-ray diffraction, infrared spectroscopy and dilatometric observations. It was confirmed that the extent of the reactions was essentially dependent on the heat treatment method. Under the hot pressing conditions dense samples containing high fraction of unreacted HAp could be prepared at 1200?C.Mechanical properties of the pure HAp and HAp-ZrO2 composites were also investigated. Zirconia inclusions lead to the increased strength, hardness and fracture toughness of the composites compared to the pure HAp polycrystalline materials.
Ceramics International, 2016
Novel hydroxyapatite-zirconia-lanthanum oxide composites for bioceramic applications were synthesized and their structural, mechanical and biological properties were studied. Pure HA was produced via precipitation method and the composites were obtained by several fabrication steps: powder milling, mixing, cold pressing and sintering at 1100°C for 1h. The experimental results indicated that the composites consisted of hydroxyapatite as the main phase with a trace amount of tricalcium phosphate. Calcium zirconate (CaZrO 3) was also formed by the reaction between zirconia and calcium oxide (CaO) which is the thermal decomposition product of hydroxyapatite. Addition of zirconia and lanthanum oxide resulted a more loose and porous structure on the surface. The diametral tensile strength of the composites was higher with respect to pure hydroxyapatite. The microhardness of the composites, except the one with the composition of 90 wt% HA and 10 wt% Zr, was relatively lower than that of pure HA but these composites had higher machinability. Cell culture studies with osteoblast-like Saos-2 cell line showed that composites and pure hydroxyapatite were biocompatible. Based on these findings, hydroxyapatite-zirconia-lanthanum oxide composites hold potential to be used in hard tissue replacement and regeneration therapies.
Journal of Biomaterials Applications, 2011
The biological response of strontium (Sr) doped hydroxyapatite (HA) and hydroxyapatite–zirconia (HA–ZrO2) composites produced by employing sol–gel technology, minimal ZrO2 loadings, and novel microwave-sintering regimes thereby retarding decomposition, is reported. In vitro evaluations indicate that all materials induce a favorable response from rat osteosarcoma cells. In vivo evaluations show osteoconductivity and biocompatibility for both the Sr–HA and HA–ZrO2. The materials did not cause any inflammatory response in bone. The Sr–HA displays better biocompatibility which may be due to the incorporation of Sr and the formation of a surface apatite layer.
Porous ZrO2 bone scaffold coated with hydroxyapatite with fluorapatite intermediate layer
Biomaterials, 2003
Highly porous zirconia (ZrO 2 ) bone scaffolds, fabricated by a replication technique using polymeric sponge, were coated with hydroxyapatite (HA). To prevent the chemical reactions between ZrO 2 and HA, an intermediate fluorapatite (FA) layer was introduced. The strength of the porous ZrO 2 was higher than that of pure HA by a factor of 7, suggesting the feasibility of ZrO 2 porous scaffolds as load-bearing part applications. The coated HA/FA layer, with a thickness of about 30 mm, was firmly adhered to the ZrO 2 body with a bonding strength of 22 MPa. The osteoblast-like cells were attached and spread well on the coating layer throughout the porous scaffolds. The alkaline phosphatase activity of the proliferated cells on the HA/FA coated ZrO 2 was comparable to that on pure HA and higher than that on pure ZrO 2 .
Zirconia–hydroxyapatite composite material with micro porous structure
Dental Materials, 2011
Objectives. Titanium plates and apatite blocks are commonly used for restoring large osseous defects in dental and orthopedic surgery. However, several cases of allergies against titanium have been recently reported. Also, sintered apatite block does not possess sufficient mechanical strength. In this study, we attempted to fabricate a composite material that has mechanical properties similar to biocortical bone and high bioaffinity by compounding hydroxyapatite (HAp) with the base material zirconia (ZrO 2), which possesses high mechanical properties and low toxicity toward living organisms. Methods. After mixing the raw material powders at several different ZrO 2 /HAp mixing ratios, the material was compressed in a metal mold (8 mm in diameter) at 5 MPa. Subsequently, it was sintered for 5 h at 1500 • C to obtain the ZrO 2 /HAp composite. The mechanical property and biocompatibility of materials were investigated. Furthermore, osteoconductivity of materials was investigated by animal studies. Results. A composite material with a minute porous structure was successfully created using ZrO 2 /HAp powders, having different particle sizes, as the starting material. The material also showed high protein adsorption and a favorable cellular affinity. When the mixing ratio was ZrO 2 /HAp = 70/30, the strength was equal to cortical bone. Furthermore, in vivo experiments confirmed its high osteoconductivity. Significance. The composite material had strength similar to biocortical bones with high cell and tissue affinities by compounding ZrO 2 and HAp. The ZrO 2 /HAp composite material having micro porous structure would be a promising bone restorative material.