P-tricalcium phosphate

Tricalcium phosphate, Ca2(P0 2> is formed under high temperatures and is unstable toward reaction with moisture below 100°C. The high temperature mineral whidockite [64418-26-4] although often described as P-tricalcium phosphate, is not pure. Whidockite contains small amounts of iron and magnesium. Commercial tricalcium phosphate prepared by the reaction of phosphoric acid and a hydrated lime slurry consists of amorphous or poody crystalline basic calcium phosphates close to the hydroxyapatite composition and has a Ca/P ratio of approximately 3 2. Because this mole ratio can vary widely (1.3—2.0), free lime, calcium hydroxide, and dicalcium phosphate may be present in variable proportion. The highly insoluble basic calcium phosphates precipitate as fine particles, mosdy less than a few micrometers in diameter. The surface area of precipitated hydroxyapatite is approximately... 

Other Ceramic Calcium Phosphate Materials. Other ceramic calcium phosphate materials for repairing bony defect iaclude p-tricalcium phosphate (P-TCP) [7758-87-4], P-Ca2(PO, and biphasic calcium phosphate (BCP) ceramics which consist of both P-TCP and HA. Unlike ceramic HA, P-TCP resorbs ia the tissue (293). The in vivo dissolution of BCP ceramic implants was shown (296) to iacrease with increasing P-TCP/HA ratio ia the implants. Both P-TCP and BCP can lead to new bone growth to various extents depending on the appHcations and the type of materials used (293,296). 

Prior to true subsurface bone spectroscopy, Penel and coworkers obtained bone Raman spectra using a titanium chamber with a fused silica window placed in the calvaria of New Zealand rabbits [2]. With this apparatus they were able to study both bone tissue and implanted hydroxyapatite and P-tricalcium phosphate over a 8-month period. In addition to bone spectra, hemoglobin spectra were obtained close to blood vessels. 

Kikuchi, M. and Tanaka, J., Chemical interaction in P-tricalcium phosphate/copo-lymerized poly-L-lactide composites, J. Ceram. Soc. Jpn., 108, 642, 2000. 

Table 3 Manufacturing data of porous ceramic pellets of P-Tricalcium Phosphate and hydroxyapatite, respectively...

Tercent density based on the true density of the starting materials. P-Tricalcium phosphate. 

A second type of implant that is used for the local antibiotic treatment of bone infections is based on p-tricalcium phosphate ceramic pellets. The pellets are prepared by granulation and subsequent thermal treatment between 975°C and 1300°C. They are loaded... 

Fig. 44 Scanning electron micrographs of the structure cross-section of porous ceramic pellets of P-tricalcium phosphate (A-C) and hydroxyapatite (D).

Similar compacts can be obtained at the lower firing temperature by the application of a higher compaction pressure. Hydroxyapatite shows differences compared with p-tricalcium phosphate leading to low densities... 

Calcium (titanium, zirconium) orthophosphate ceramics show solubility in SBF at least one order of magnitude lower than that of other calcium orthophosphates including hydroxyapatite and, in particular P-tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP) (Figure 4.20). 

Figure 4.21 Solubility isotherms of calcium phosphates at 25 °C. HAp, hydroxyapatite DCPD, brushite DCPA, monetite p-TCP, p-tricalcium phosphate OCP, octacalcium phosphate and TTCP, tetracalcium phosphate. (After De Groot et al. (1990).)...

Yashima, M., Sakai, A., Kamiyama, T., and Hoshikawa, A. (2003) Crystal structure analysis of P-tricalcium phosphate Ca3(P04)2 by neutron diffraction. J. Solid State Chem., 175 (2), 272-277. 

Figure 7.2c represents a situation of advanced thermal decomposition during which P-tricalcium phosphate (fl-TCP, denoted by 3 ) and TTCP (denoted by 4 ) have been formed (step 3 of Table 6.7). Finally, in Figure 7.2d an even stronger decomposition of either orthophosphate towards CaO (denoted by 1 ) has occurred (step 4 of Table 6.7) owing to a shorter spray distance (240 mm) and substrate preheating. 

Figure 7.9 Raman standard spectra of tetracal-cium phosphate (TTCP, (a)), p-tricalcium phosphate (P-TCP, (b)) and hydroxyapatite (HAp, (c)).

Figure 1. Solubility isotherms of calcium phosphate phases in the system Ca(0H)2-H3P04-H20 at 37°C. DCPD is dicalcium phosphate dihydrate, brashite DCPA is dicalcium phosphate anhydrous, monetite OCP is octacalcium phosphate p-TCP is p-tricalcium phosphate and OHAp is hydroxylapatite. pignre 1.1 from Elliott (1994), reprinted with permission from Elsevier Science.]...

Bioresorbable p-tricalcium phosphate is occasionally used in conjunction with hydroxylapatite to improve solubility (Klein et al. 1984, Yamada et al. 1997) and hence the osteoconductivity. Applications include nose reconstruction (Abe et al. 2001), fusion of the backbone (Ueda et al. 2001), and use as a bone graft (Fujibayashi et al. 2001). 

Figure 9. Solubility of hydroxylapatite compared to oxyapatite, amorphous calcium phosphate, tetracaleium phosphate (TTCP), a-tricalcium phosphate and P-tricalcium phosphate determined in O.IM potassium acetate at pH 6 (modified from Le Geros et al. 1995).

Apatitic TCP (ap>-TCP) Ca9(HP04)(P04)5(0H) is a calcium orthophosphate which, during thermal treatment at temperature higher than 750°C, transforms onto P-tricalcium phosphate Ca3(P04)2. 

A pure P-tricalcium phosphate phase Ca3(P04)2, obtained using the following synthesis parameters final pH=5,8 and T= 22 °C (synthesis 4), it is synthesized at low temperatures and pH is acidic. 

J. (2004) Development of guided bone regeneration membrane composed of P-tricalcium phosphate and poly (1-lactide-co-glycolide-co-e-caprolactone) composites. Biomaterials, 25 (28), 5979-5986. 

S. Kotani, Y. Fujita, T. Kitsugi, T. Nakamura, T. Yamamuro, C. Ohtsuki and T. Kokubo (1991) Bone Bonding Mechanisms of p-tricalcium Phosphate, /. Biomed. Maters. Res. 25, 1303-15. 

M. Jarcho, R.L. Salsbury, M.B. Thomas and R.H. Doremus, Synthesis and Fabrication of p-tricalcium Phosphate (Whitlockite) Ceramics for Potential Prosthetic Applications, J. Mater. Sci. 14, 142-150 (1979). 

In neutral or alkaline solutions, the order of stability (insolubility) is hydroxyapatite > P-tricalcium phosphate > octacalcium phosphate > dicalcium phosphate (monetite) > dicalcium phosphate dihydrate (brushite) > monocalcium phosphate. Below pH 4.8, however, monetite and brushite are the most stable and insoluble phases, although these acid salts dissolve incongruently in water (see below). 

In recent years, attention has been paid to biphasic ceramics which are aimed at securing an optimum balance between the more stable hydroxyapatite, and the more soluble and better bonding P-tricalcium phosphate which is bio-resorbable [26]. 

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