The mineral or inorganic component of bone is a calcium phosphate idealized as a calcium hydroxyapatite, HA, Ca10(PO4)6(OH)2. Changes in the composition of the apatite affect its lattice parameters, morphology, crystallinity (reflecting crystal size and/or perfection) and finally dissolution properties. In regard to the above points, lattice parameters are expected to have better dissolution properties. Estimation of HA nanocrystallite size lattice parameters is one of the most important factors for dissolution properties of bone apatites. In present work, the composition of apatite induce complex structures at the unit-cell level and play a role in influencing the dissolution rate of apatites, which may favour osteointegration. The samples are consist of NHA, bovine bone heated at 850 °C for 3 h; BHA, human bone heated at 900 oC for 2 h and PHA, HA pure powder. The results estimated by XRD data indicate that increasing in c/a ratio of HA, which is leading to increasing in crystallinity, induce decrease at HA dissolution or improving its chemical solubility in simulated body fluid (SBF). As, it was concluded that the biodegradation of HA decrease in PHA sample.
This work began with preparing hydroxyapatite from bovine bones and continued with doping fluorine into hydroxyapatite matrix to produce fluorine-doped hydroxyapatite in optimum conditions. At the end a fluorine hydroxyapatite–zircon nanocomposite ceramic with good bioactivity and good chemical stability was synthesized through a mechano-chemical route and subsequent two step sintering process. The ability of apatite formation on the produced nanocomposite samples, as a yardstick for evaluation of the bioactivity, was estimated by using simulated body fluid. According to the results obtained, after soaking the nanocomposite samples in the fluid solution, the pH value was increased during the first week of experiments. Furthermore, the concentration of the Ca ions at the end of the second week in the fluid solution was dependent on the Si – OH nucleation sites on the surface of nanocomposite.
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