Ca/P molar ratio

As shown in Fig. 7.15, all the X-ray diffraction peaks of CPI.5, CPI. 67 and CP2 samples belong to HAp. As the Ca/P molar ratio deacases from 1.375, the peak intensity of HAp decreases appreciably, while that of monetite and brushite increases. The effect of NH3 adding is shown in Fig. 7.16. 

Ponder C, Viana M. Energetic yields in apatitic calcium phosphate compression influence of the Ca/P molar ratio. Polymer International 2003 52(4) 625-628. 

Semi-quantitative XPS analyses on the calcium phosphate deposits revealed that due to the inhibition and dissolution effects of citric acid, the calcium phosphates have Ca/P molar ratios between 0.5 and 1.2. These values are lower than the Ca/P molar ratios for the deposits formed on PHEMA containing no... 

Semi-quantitative X-ray analyses on the calcium phosphate deposits based on Figure 6A (EDS data) and Figure 7 A (XPS data) provided Ca/P molar ratios of 1.52 and 1.55, respectively. A Ca/P molar ratio of 1.50 suggests that the white deposits found on the PHEMA samples may be mainly Ca2+ and OH deficient hydroxyapatite (PHAp), with carbonate and brushite (DCPD) as the major impurities. 

Stoichiometry, described by the Ca/P molar ratio, has a major influence on the physical properties of the apatite and, hence, its application. For calcium-deficient hydroxylapatite, a decrease in surface area starting at 700°C leads to a lower shrinkage (8% less for a powder with Ca/P of 1.64 relative to stoichiometric HAp at 1200°C) (Raynaud et al. 2002b). Low shrinkage in the final sintered product is usually accom-... 

An important chemical aspect of apatites for biomedical use is the Ca/P molar ratio. Synthesized apatites may be calcium deficient or rich and yet display an X-ray diffraction pattern typical of apatite. Those apatites that are subjected to low temperature processing such as cements and biomimetically processed coatings require a wet chemical analysis for determination of the Ca/P molar ratio. With the new interest in chemically modified apatites, the Ca/P molar ratio, the impurity elements according to present standards (ASTM 1998) and the major substituent elements will need to be reported to provide a better understanding of the apatites being investigated for biomedical applications. 

Age of rat femurs, days Ash, % Ca/P, molar ratio SF Mineral content, % ... 

Depending on the calcium/ phosphorus (Ca/P) molar ratio and solubility of the compound, it is possible to obtain numerous calcium phosphates of different composition. Molar Ca/P ratio and solubility are connected with the pH of the solution. Majority of materials of this class are resorbable and dissolve when inserted in a physical environment. Calcimn phosphates that are most frequently used in the biomaterial field are demonstrated in Table 1 (Dorozhkin, 2009c El Kady, 2009 Shi, 2006). 

ICP-AES analyses confirmed that the coated substance is Mg-doped calcium phosphate. ICP-AES analyses (5 analyses on 5 repetition samples) indicated the presence of 1568 45 ppm Mg in the coated substance having a Ca/P molar ratio of 1.40 0.11. ATR-FTIR data of DMEM-coated Ti coupons are shown in Fig. 3, together with those of as received grade-1 Ti and alkali-treated grade-1 Ti. 

The inorganic salt solution (with a Ca/P molar ratio of 2.5) of Table 1 was much faster, in comparison to the DMEM solutions, in depositing X-ray amorphous CaP globules with extremely smooth surfaces on the alkali-treated grade-1 Ti samples at 37 C (Figs. 4a and 4b). 

We previously reported the complete transformation of brushite (DCPD, dicalcium phosphate dihydrate, CaHP04-2H20) powders in less than a week to octacalcium phosphate (OCP), but not to apatitic calcium phosphate, when a commercial DMEM solution was used as the soak test medium at 37°C [42]. The removal of all the amino acids, vitamins, ucose/dextrose, phenol red, Hepes and pyruvate from the DMEM formulation and raising the Ca/P molar ratio of thus modified form of biomineralization solution from 1.99 to 2.50 led to observing much faster transformation of DCPD powders to OCP in comparison to DMEM [43]. 

This study reports a newly discovered ability of an easy-to-prepare, initially precipitate-free, Tris- or Hepes-free solution we formulated, with a HCOs concentration of 44 mM, a pH of 7.4, and a Ca/P molar ratio of 2.50,... 

One liter of the new biomineralization medium of this study was prepared by adding the indicated amounts of chemicals in Table 1, in the order given, to 998 mL of pre-boiled deionized water. As-prepared solutions had a pH value (7.45 0.05 at both room temperature, 22 1°C, and 65 0.3°C) similar to that of blood plasma. ACP powder syntheses were performed in heat-sterilized (130°C, 8 h) and unused Pyrex glass media bottles. Inorganic ion concentrations shown in Table 1 strictly mimic those of the DMEM solutions with the only exception of Ca . The calcium concentration of the original DMEM solution was intentionally increased in this study from 1.80 to 2.26 mM to attain a Ca/P molar ratio of 2.50 i.e., that of human blood) in the biomineraiization medium. The solutions were stored in clean and sealed glass bottles in a... 

Microscale hydroxyapatite (size distribution of the powder 3.0 0.1 J,m) similar to the innate hydroxyapatite in human bone (57.0 and 41.4 wt% of CaO and P2O5, respectively Ca/P molar ratio 1.67) was used to fabricate films after suspension in solutions of 400 kDa chitosan. Becanse of the well-dispersed hydroxyapatite powders in the polymer matrix, the film appeared white and flexible with a transmittance <20% in the visible range. The observation under the SEM ensnred monodis-persity of the films. Good monodispersity improved the homogeneity and uniformity of the film, and prevented phase separation resulting in unwanted microcracks (Kim et al. 2009). 

Table A3.5 Ca/P Molar Ratio of Human Enamel and Dentin...

Enamel Ca/P molar ratio Dentin Ca/P molar ratio Source, comments... 

---