



@article {2572,
	title = {Glass-reinforced hydroxyapatite composites: Secondary phase proportions and densification effects on biaxial bending strength},
	journal = {Journal of Biomedical Materials ResearchJ. Biomed. Mater. Res.},
	volume = {48},
	year = {1999},
	note = {Cited By (since 1996): 28Export Date: 21 November 2012Source: ScopusCODEN: JBMRBdoi: 10.1002/(SICI)1097-4636(1999)48:5<734::AID-JBM20>3.0.CO;2-2PubMed ID: 10490690Language of Original Document: EnglishCorrespondence Address: Santos, J.D.; INEB-Instituto Engenharia Biomedica, Laboratorio de Biomateriais, Rua do Campo Alegre, 823, 4150 Porto, PortugalChemicals/CAS: alpha-tricalcium phosphate; Biocompatible Materials; calcium phosphate, 10103-46-5; Calcium Phosphates; dicalcium phosphate anhydrous, 7757-93-9; Hydroxyapatites; monocalcium phosphate; tetracalcium phosphateReferences: Yamamuro, Y., Hench, L.L., Wilson, J., (1990) CRC Handbook of Bioactive Ceramics, , Boca Raton, FL: CRC;Rice, R.W., Microstructure dependence of mechanical behaviour (1977) Treatise on Materials Science and Technology, 11. , MacCrone RK, editor. New York: Academic; 
Rice, R.W., Grain size and porosity dependence of ceramic fracture energy and toughness at 22{\textdegree}C (1996) J Mat Sci, 31, pp. 1969-1983; 
Santos, J.D., Knowles, J.C., Reis, R.L., Monteiro, F.J., Hastings, G.W., Microstructural characterisation of glass reinforced hydroxyapatite composites (1994) Biomaterials, 15, pp. 5-10; 
Lopes, M.A., Knowles, J.C., Santos, J.D., Monteiro, F.J., Olsen, I., Flow cytometry for assessing biocompatibility (1998) J Biomed Mater Res, 41, pp. 649-656; 
Wayne, S.F., Buljan, S.T., Microstructure and wear resistance of silicon nitride composites (1994) Friction and Wear of Ceramics, p. 261. , Jahanmir S, editor. New York: Marcel Dekker; 
Kaysser, W.A., Sprissler, M., Handwerker, C.A., Blendell, J.E., Effect of liquid phase on the morphology of grain growth of alumina (1987) J Am Ceram Soc, 70, pp. 339-343; 
Lopes, M.A., Santos, J.D., Monteiro, F.J., Knowles, J.C., Glass reinforced hydroxyapatite: A comprehensive study of the effect of glass composition on the crystallography of the composite (1998) J Biomed Mater Res, 39, pp. 244-251; 
Soltesz, U., Ritcher, H., Kienzler, R., The concentric-ring test and its applications for determining the surface strength of ceramics (1987) High Tech Ceram, pp. 149-159. , Amsterdam: Elsevier; 
Murtage, B., (1981) Advance Linear Programming, , New York: McGraw-Hill; 
Cha{\textquoteright}tal, V., (1990) Linear Programming, , New York: Freeman; 
Davidge, R.W., (1986) Mechanical Behaviour of Ceramics, , Cambridge: Cambridge Univ Press; 
German, R.M., (1985) Liquid Phase Sintering, , New York: Plenum; 
Akao, M., Aoki, H., Kato, K., Mechanical properties of sintered hydroxyapatite for prosthetic applications (1981) J Mater Sci, 16, pp. 809-812; 
Fanovich, M.A., Lopes, J.M.P., Influence of temperature and additives on the microstructure and sintering behaviour of hydroxyapatites with different Ca/P ratios (1998) J Mat Sci Mat Med, 9, pp. 53-60; 
Jarcho, M., Bolen, C.H., Bobik, J., Kay, J.F., Doremus, R.H., Hydroxyapatite synthesis and characterisation in dense polycrystalline form (1976) J Mat Sci, 11, pp. 2027-2035; 
Van Landuyt, P., Li, F., Keustermans, J.P., Streydio, J.M., Delnnay, F., Munting, E., The influence of high sintering temperatures on the mechanical properties of hydroxyapatite (1995) J Mat Sci Mat Med, 6, pp. 8-13; 
Aoki, H., (1991) Science and Medical Applications of Hydroxyapatite, , Japanese Association of Apatite Layer; 
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Barsoum, M., Fundamentals of Ceramics, , New York: McGraw-Hill; 1997
},
	month = {1999///},
	pages = {734 - 740},
	publisher = {John Wiley \& Sons Inc},
	abstract = {CaO-P                        2O
                        5 glasses with additions of MgO and CaF
                        2 were used as a sintering aid of hydroxyapatite, and glass-reinforced hydroxyapatite composites obtained. Glasses promoted significant changes in the microstructure of the composites, namely with the formation of tricalcium phosphate secondary phases, β and α-TCP. Quantitative phase analysis was performed by the Rietveld method using General Structure Analysis Software. Grain size measurements were carried out on SEM photomicrographs, using a planimetric procedure according to ASTM E 112-88. Flexural bending strength was determined from concentric ring-on-ring testing. Flexural bending strength (FBS) of glass-reinforced hydroxyapatite composites was found to be about twice or three times higher than that of unreinforced hydroxyapatite and tended to depend more on porosity and β and α-TCP secondary phases, rather than on grain size. Traces of α-tricalcium phosphate significantly enhanced the strength of the composites. Using the rule of mixtures to estimate the zero porosity bending strength, the Duckworth-Knudsen model applied to the composites gave a porosity correction factor, b, with a value of 4.02. Weibull statistics were also used to analyze biaxial strength data and the level of reinforcement obtained by comparing failure probability for the composites and for the unreinforced hydroxyapatite. Lower activation energies for grain growth were observed for the composites compared to unreinforced hydroxyapatite, which should be attributed to the presence of a liquid glassy phase that promotes atomic diffusion during the sintering process.
CaO-P
                        2O
                        5 glasses with additions of MgO and CaF
                        2 were used as a sintering aid of hydroxyapatite, and glass-reinforced hydroxyapatite composites obtained. Glasses promoted significant changes in the microstructure of the composites, namely with the formation of tricalcium phosphate secondary phases, β and α-TCP. Quantitative phase analysis was performed by the Rietveld method using General Structure Analysis Software. Grain size measurements were carried out on SEM photomicrographs, using a planimetric procedure according to ASTM E 112-88. Flexural bending strength was determined from concentric ring-on-ring testing. Flexural bending strength (FBS) of glass-reinforced hydroxyapatite composites was found to be about twice or three times higher than that of unreinforced hydroxyapatite and tended to depend more on porosity and β and α-TCP secondary phases, rather than on grain size. Traces of α-tricalcium phosphate significantly enhanced the strength of the composites. Using the rule of mixtures to estimate the zero porosity bending strength, the Duckworth-Knudsen model applied to the composites gave a porosity correction factor, b, with a value of 4.02. Weibull statistics were also used to analyze biaxial strength data and the level of reinforcement obtained by comparing failure probability for the composites and for the unreinforced hydroxyapatite. Lower activation energies for grain growth were observed for the composites compared to unreinforced hydroxyapatite, which should be attributed to the presence of a liquid glassy phase that promotes atomic diffusion during the sintering process.
},
	keywords = {article, atom, Bending (deformation), Biocompatibility, Biocompatible Materials, Biomaterials, calcium fluoride, calcium phosphate, Calcium phosphates, Composite materials, Densification, Dental application, dentistry, Duckworth-Knudsen model, glass, Glass reinforced hydroxyapatite, Humans, hydroxyapatite, Hydroxyapatite-glass composites, Hydroxyapatites, Implants (surgical), Magnesium Oxide, mathematical analysis, Mechanical strength, Mechanics, Medical applications, Microstructure, orthopedics, Phase composition, physical chemistry, porosity, Scanning electron microscopy, Strength of materials, tensile strength, Tissue, Tricalcium phosphate},
	isbn = {00219304 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-0032868650\&partnerID=40\&md5=e6fa831a838301db0336e9010a0800dd},
	author = {Lopes, M.A. and Monteiro, F.J. and Santos, J.D.}
}
