Calcium-deficient hydroxyapatite

Once calcium deficient hydroxyapatite DOHA (between pH 6.8 and 8.2) is formed, a metastable equilibrium is created with the aqueous solution which may last indefinitely at room or body temperature.If carbonate ions are present in addition the apatite preferably formed is... 

The dehydration of alcohols on stoichiometric and nonstoichiometric (calcium-deficient) hydroxyapatite (series 8 and 9 in Table II) gave results consistent with the above findings. Although there is a difference in the reaction temperature, it is evident that with the nonstoichiometric catalyst, which must be more acidic, the slope found is more negative than that with the stoichiometric calcium phosphate. 

As well as being used as a scaffold for tissue engineering, Hutchens et al. [64] described the creation of a calcium-deficient hydroxyapatite, the main mineral component of bone. Calcium phosphate particles were precipitated in BC by consecutive incubation of calcium chloride and sodium phosphate solutions. Initial tests with osteoblasts in the in vitro evaluation showed that solid fusion between the material and the bone tissue is possible. Hence, this material is a good candidate for use as a therapeutic implant to regenerate bone and heal osseous damage. 

Posner, A.S., Stutman, J.M., and Lippincott, E.R. (1960) Hydrogen bonding in calcium-deficient hydroxyapatite. Nature, 188,... 

More complexity is introduced by the fact that deviation from stoichiometry leads to precipitation of calcium-deficient hydroxyapatite (1.33 < Ca/P < 1.67) with the approximate formula Ca HPOJ POJg OH) with 0 < x < 2. If = 2, one obtains OCP, x = 1 leads to TCP and x = 0 to hydroxyapatite. 

F. (2014) Effect of amorphous phases during the hydraulic conversion of a-TCP into calcium-deficient hydroxyapatite. Acta Biomater. 10 (9), 3931-3941. 

Fulmer M.T., Martin R.I., and Brown P.W. 1992. Formation of calcium deficient hydroxyapatite at near-physiological temperature. /. Mat. Sci Mater. Med. 3 299-305. 

It has been suggested that the mineral portions of bone and tooth tissue are calcium-deficient hydroxyapatites (Posner and Perloff, 1957 Neuman and Neuman, 1953). The possible presence of hydrogen bonds in these materials may provide a much needed parameter for an estimation of the stoichiometry of these biological hydroxyapatites under varying conditions (Posner et al, 1960). 

Y.E. Greish, et al.. Formation and properties of composites comprised of calcium-deficient hydroxyapatites and ethyl alanate poly-phosphazenes, J. Mater. Sci. Mater. Med. 19 (9) (2008) 3153—3160. 

Table 2.1 Main calcium phosphate compounds. The first six compounds precipitate at room temperature in aqueous systems. The last six compounds are obtained by thermal decomposition or thermal synthesis. The five columns contain the name, the corresponding chemical formula, the Ca to P molar ratio, the mineral name, and the typical acronym, respectively. When x > 0 in the chemical composition of precipitated hydroxyapatite, one talks also about calcium-deficient hydroxyapatite (CDHA). Generally, x= 1 so that in most cases CDHA has the composition Ca9(HP04) (P04)60H...

N. Dumelie, H. Benhayoune, D. Richard, D. Laurent-Maquin, and G. Balossier, In vitro Precipitation of Electrodeposited Calcium-deficient Hydroxyapatite Coatings on Ti6A14V Substrate, Mater. CharacL, 59,129-33 (2008). 

Dumelie N, Benhayonne H, Richard D, Laurent-Maqnin D, Balossier G. In vitro precipitation of electrodeposited calcium-deficient hydroxyapatite coatings on Ti6A14V substrate. Mater Character 2008 59 129-33. 

Intensive investigations on preparation, characterization, and application experiments of bacterial nanocellulose tubes are also reported by Helenius et al. (2006) and Bodin et al. (2007a). As part of investigations on bone repair, Hutchens et al. (2006) demonstrated by combination of hydroxyapatite and bacterial nanocellulose that bacterial nanocellulose provides a template for the ordered formation of calcium-deficient hydroxyapatite (CDHAP), the natural mineral component of bone. An... 

Figure 10,2 Typical scanning electron microscopy (a,b) and transmission electron microscopy images (e,f) of synthetic and eggshell-derived calcium-deficient hydroxyapatite. Energy-dispersive X-ray spectra (c,d) and selected area electron diffraction pattern are shown in the inset.

Siddharthan A, Seshadri SK, Sampath Kumar TS (2004) Microwave accelerated synthesis of nanosized calcium deficient hydroxyapatite. J Mater Sci Mater Med 15 1279-1284... 

Hutchens SA, Benson RS, Evans BR, O Neill HM, Rawn CJ. Biomimetic synthesis of calcium-deficient hydroxyapatite in a natural hydrogel. Biomaterials 2006 27 4661-70. 

Durucan C, Brown PW (2000) Low temperature formation of calcium-deficient hydroxyapatite-PLA/PLGA composites. J Biomed Mater Res 51 717-725... 

Kasten, R, Luginbuhl, R., van Griensven, M., Barkhausen, T., Krettek, C., Bohner, M., and Bosch, U. 2003. Comparison of human bone marrow stromal cells seeded on calcium-deficient hydroxyapatite, P-tricalcium phosphate and deminerahzed bone matrix. Biomaterials 24 2593-603. 

The formation of calcium-deficient hydroxyapatite (Ca/P = 1.50) can be represented as follows ... 

Octacalcium phosphate (OCP) — amorphous calcium phosphate (AGP) calcium-deficient hydroxyapatite (DCP or CDHA) hydroxyapatite. 

Liu, T.Y., Chen, S.Y., Liu, D.M. and Liou, S. (2005) On the study of BSA-loaded calcium-deficient hydroxyapatite nano-carriers for controlled drug delivery. Journal of Controlled Release, 107,112-21. 

Akiyama N, Takemoto M, Fujibayashi S, Neo M, Hirano M, Nakamura T. Difference between dogs and rats with regard to osteoclast-like cells in calcium-deficient hydroxyapatite-induced osteoinduction. J Biomed Mater Res Part A 2011 96A(2) 402-12. 

Tenhuisen KS, Brown PW. The effects of citric and acetic acid on the formation of calcium deficient hydroxyapatite at 38°C. / Mater Sci, Mater Med 1994 5 291-298. 

Posner, A. S., J. M. Stutman, and E. R. Lippincott, 1960. Hydrogen bonding in calcium-deficient hydroxyapatites. Nature 188 486. 

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