Hydroxyapatite properties

Recipes from 12531-2534] Four synthetic hydroxyapatites. Properties FTIR spectra, SEM images available [349] see also Table 3.1765. 

Vitahium FHS ahoy is a cobalt—chromium—molybdenum ahoy having a high modulus of elasticity. This ahoy is also a preferred material. When combiaed with a properly designed stem, the properties of this ahoy provide protection for the cement mantle by decreasing proximal cement stress. This ahoy also exhibits high yields and tensile strength, is corrosion resistant, and biocompatible. Composites used ia orthopedics include carbon—carbon, carbon—epoxy, hydroxyapatite, ceramics, etc. 

Blumenthal, N.C., Belts, F. and Posner, A.S. 1975 Effect of carbonate and biological macromolecules on the formation and properties of hydroxyapatite. Calcified Tissue Research 18 81-90. 

Chen, C.-W., Oakes, C.S., Byrappa, K., Riman, R.E., Brown, K., TenHuisen, K. S. and Janas, V.F. (2004) Synthesis, characterization, and dispersion properties of hydroxyapatite prepared by mechanochemical-hydrothermal... 

Padilla, S., Vallet-Regi, M., Ginebra, M. P. and Gil, F.J. (2005) Processing and mechanical properties of hydroxyapatite pieces obtained by the gelcasting method. Journal of the European Ceramic Society, 25, 375-383. 

Venugopal and Scurrell544 reported low temperature shift activity for 3%Ru/ Caio(P04)6(OH)2 and 3%Au/Ca10(PO4)6(OH)2, the support being hydroxyapatite, a material that is similar to the mineral component of bones. A comparison of their activities is provided in Table 132, along with the catalyst properties. 

Bone and teeth in mammals and bony fishes all rely on calcium phosphates in the form of hydroxyapatite [Ca5(P04)30H]2, usually associated with around 5% carbonate (and referred to as carbonated apatite). The bones of the endoskeleton and the dentin and enamel of teeth have a high mineral content of carbonated apatite, and represent an extraordinary variety of structures with physical and mechanical properties exquisitely adapted to their particular function in the tissue where they are produced. We begin by discussing the formation of bone and then examine the biomineralization process leading to the hardest mineralized tissue known, the enamel of mammalian teeth. 

Daglia, M. Tarsi, R. Papetti, A. Grisoli, R Dacarro, C. Pruzzo, C. Gazzani, G. Antiadhesive Effect of Green and Roasted Coffee on Streptococcus mutans Adhesive Properties on Saliva-Coated Hydroxyapatite Beads, j. Agric. Food Chem. 2002, 50, 1225-1229. 

Chlorhexidtne is a symmetrical cationic molecule that is most stable as a salt the highly water-soluble digluconate is the most commonly used preparation. Because of its cationic properties, it binds strongly to hydroxyapatite (the mineral component of tooth enamel), the organic pellicle on the tooth surface, salivary proteins, and bacteria. Much of the chlorhexidine binding in the mouth occurs on the mucous membranes, such as the alveolar and gingival mucosa, from which sites it is slowly released in active form. 

M.S. Tung, D. Skrtic, Interfacial properties of hydroxyapatite in fluorapatite and octa-calcium phosphate, in L.C. Chowm, E.D. Eanes (Eds.), Octacalcium Phosphate, Karger, Basel, 2001, pp. 112-129. 

The various findings about fluoride and its interaction with the hydroxyapatite at the molecular level show that the relationship is complicated and multifaceted. The broad conclusion from the enormous volume of work that has led to our current understanding of the role of fluoride is that it is overwhelmingly beneficial. It promotes numerous desirable properties in tooth mineral, reducing solubility through action in both the saliva and in the mineral phase, it shifts the demineralisation/remineralisation equilibrium in favour of remineralisation, and through its actions in the solid state, ensures that the kinetically favoured OCP is transformed into the more thermodynamically stable hydroxyapatite. Research continues, and there is no doubt that there is still more to learn about the complexities of the interaction of fluoride with hydroxypatite under physiological conditions. 

Apatite surface properties have been characterized with respect to their role as sorptive surfaces (Wu et al. 1991 Somasundaran Wang 1984 Chander Fuerstenau 1984 Leyva et al. 2001). The point of zero charge (PZC), as measured by titration, electrophoresis, or streaming potential varies from pH values of 7 to 10 for hydroxyapatite and from 4 to 12 for fluoroapatite, and is a function of (1) the presence of C02, (2) ionic strength, and (3) time/aging of the mineral. 

Chander, S. Fuerstenau, D. W. 1984. Solubility and interfacial properties of hydroxyapatite a review. In Misra, D. N. (ed) Adsorption and Surface Chemistry of Hydroxyapatite. Plenum Press, New York, 28-49. 

Mandjiny, S., Matis, K. A. et al. 1998. Calcium hydroxyapatites evaluation of sorption properties for cadmium ions in aqueous solution. Journal of Materials Science, 33, 5433-5439. 

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