Apatite composition

Zhang, R. and Ma, P.X. (1999) Porous poly(L-lactic acid)/apatite composites created by biomimetic process. Journal of Biomedical Materials Research, 45, 285-293. 

Uchida, M., Oyane, A., Kim, H.-M., Kokubo, T. and Ito, A. (2004) Biomimetic coating of laminin-apatite composite on titanium metal and its excellent cell-adhesive properties. Advanced Materials, 16, 1071-1074. 

Oyane, A., Uchida, M. and Ito, A. (2005) Laminin-apatite composite coating to enhance cell adhesion to ethylene-vinyl alcohol copolymer. Journal of Biomedical Materials Research, 72A, 168-174. 

Poly(oxyethylene)-Si02 ormosils have been prepared as an approach to the preparation of biologically active polymer-apatite composites. For this purpose, Yamamoto et al. [72] obtained these Class II hybrids from triethoxysilyl-terminated poly(oxyethylene) (PEG) and TEOS by using the in situ sol-gel process. After being subjected to the biomimetic process to form the bone-like apatite layer, it was found that a dense apatite layer could be prepared on the hybrid materials, indicating that the silanol groups provide effective sites for CHA nucleation and growth. 

Analyses revealed a fluor-apatite composition with an average formula. 

From a materials perspective there are two possible reasons why dental enamel shows the large variations in mechanical properties shown in figure 1 firstly, chemical variations in apatite composition and, secondly, changes in enamel structure with position from the occlusal surface to the EDJ. The chemical composition of enamel can be examined with a lateral resolution of 1-10 pm with electron microprobe analysis. Enamel structure can be obtained with SEM. To perform an accurate microprobe analysis, natural and synthetic minerals are used as standards to calibrate the instrument. This is fairly routine for geologists and earth scientists who are able to obtain chemical compositions with an accuracy of <0.1% for a wide range of elements simultaneously (including Na, Mg, Al, Si, P, K, Ca, Ti, Cr, Mn, Fe, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb, Hf, Ta, Pb, Th, U, F and Cl). In enamel only a few of these (Na, Mg, Al, P, K, Ca, Ti, Cl and F) are above the detection limit. The Ti is likely to be an impurity or contaminant rather than a constituent of enamel. This technique does not work for lighter elements such as C, S, O and N which may be present in enamel. 

Andersson,., Areva, S., Spliethoff, B., and Linden, M. (2005) Sol-gel synthesis of a multifunctional, hierarchically porous silica/apatite composite. Biomaterials, 26 (34), 6827-6835. 

Meurer WP, Boudreau AE (1996) An evaluation of models of apatite compositional variabihty using apatite from the Middle Banded Series of the Stillwater Complex, Montana. Contrib Mineral Petrol... 

Apatite composition. The compositions of metamorphic apatite typically fall along the F-OH join, although apatite with small amounts of Cl has been reported from metamorphic rocks (e.g., Kapustin 1987). Most, if not all, metamorphic apatite is dominated by the F end-member (i.e., fluor-apatite). A survey of analyses is shown in Figures 1 and 2. The F/(F+OH) typically ranges from 0.4 to 1.0 with a median value of 0.85 (Fig. la). Thus, it appears that the widespread presence of apatite in metamorphic rocks may be as much a function of the availability of F as it is the availability of P. (It should be noted that many published apatite analyses have reported F values in excess of the maximum permitted by stoichiometry, presumably due to analytical difficulties measuring F in apatite on the BMP as discussed by Stormer et al. 1993). 

Figure 1. (a) Ternary F-OH-Cl plot of metamorphic apatite compositions from pelites from central New England, USA (from Pyle 2001). (b) Compositions of metamorphic apatite separated by metamorphic grade. Note that maximum Cl content decreases and F/(F+OH) increases with metamorphic grade. Data from Kapustin (1984). 

Apatite, monazite, and xenotime are found in rocks of nearly every metamorphic grade and, apparently, have wide P-T stability ranges. Despite their widespread occurrence, surprisingly few studies on the prograde metamorphic evolution of phosphates have been published. Kapustin (1987) reported on apatite compositions as a function of metamorphic grade (e.g., Fig. lb). 

Yaidley BWD (1985) Apatite composition and fugacities of HF and HCl in metamorphic fluids. Mineral Mag 49 77-79... 

Figure 3. The effects of parent distribution on the fraction of a particles retained (Fj), following equations given by Farley et al. (1996). Calculations are for stopping of a particles in a 75 pm radius sphere of apatite composition. For a homogeneous parent distribution, Ft for this sphere would be 0.81. The top two panels show the maximum possible departure from this value all the parent located more than 1 stopping distance from the rim (maximum), and all parent on the outermost 1 pm (miitimum). All other distributions, such as the three shown, must fall between these bounds.

O Sullivan PB, Parrish RR (1995) The importance of apatite composition and single-grain ages when interpreting fission track data from plntonic rocks A case study from the Coast Ranges, British Colnmbia. Earth Planet Sci Lett 132 213-224... 

Figure 3. An Ashby diagram with the modulus of sintered hydroxylapatite, porous hydroxylapatite and polymer-apatite composites.

Osaka A, Mima Y, Takeuchi K, Asada M, Takahashi K (1991) Calcium apatite prepared from calcium hydroxide and orthophosphoric acid. J Mater Sci Mater in Med 2 51-55 Osaka A, Tsura K, lida H, Ohtsnki C, Hayakawa S, Miura Y (1997) Spray pyrolysis preparation of apatite-composite particles for biological application. J Sol-Gel Sci Technol 8 655-61 Otsuka M, Matsuda Y, Suwa Y, Fox JL, Higuchi W1 (1995) Effect of particle size of metastable calcium phosphates on mechanical strength of a novel self-setting bioactive calcium phosphate cement. J Biomed Mater Res 29 25-32... 

M. Uchida, A. Ito, K.S. Furukawa, K. Nakamura, Y. Onimura, A. Oyane, T. Tateishi, et al.. Reduced platelet adhesion to titanium metal coated with apatite, albumin-apatite composite or laminin-apatite composite. Biomaterials 26 (34) (2005) 6924-6931. 

R. Zhang, PX. Ma, Biomimetic polymer/apatite composite scaffolds for mineraUzed tissue engineering, Macromol. Biosci. 4 (2)... 

R.A. Young, Large eifects from small differences in apatite composition, in Proc. 2nd Int. Congr. Phos. Compounds, Boston, USA, 1980. 

Wei, G. B. Ma, P. X. 2006. Macroporous and nanofibrous polymer scaffolds and polymer/bone-like apatite composite scaffolds generated by sugar spheres. Journal of Biomedical Materials Research Part A, 78A, 306-315. 

Wan ACA, KhorE, Hastings GW (1998) Preparation of a chitin-apatite composite by in situ precipitation onto praous chitin scaffolds. J Biomed Mater Res 41 541-548... 

Karam et al. [10] reported the effect of 25 kGy gamma radiation on the mechanical properties of high-density apatite composites. These workers compared mechanical and thermal properties of unirradiated and irradiated samples. They concluded that these composites are potential candidates for biomechanical applications. 

Davidenko, N., Carrodeguas, R., Peniche, C., Solis, Y, and Cameron, R. (2010). Chitosan/ apatite composite beads prepared by in situ generation of apatite or Si-apatite nanocrystals. Acta Biomaterials 6, 466-476. 

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