Liquid phase sintering of hydroxyapatite by phosphate and silicate glass additions: structure and properties of the composites |
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Authors: | J D Santos R L Reis F J Monteiro J C Knowles G W Hastings |
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Affiliation: | (1) INEB-National Institute for Biomedical Engineering, Department of Metallurgical Engineering, FEUP, University of Porto, Rua dos Bragas, 4099 Porto Codex, Portugal;(2) IRC in Biomedical Materials, Queen Mary & Westfield College, University of London, Mile End Road, E1 4NS London, UK |
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Abstract: | Phosphate- and silicate-based glasses were added to hydroxyapatite in order to improve its mechanical properties and to fabricate composites with different degrees of bioactivity. A strong chemical bonding was obtained between hydroxyapatite and the phosphate-based glasses leading to samples approaching theoretical density, according to density measurements and scanning electron microscopy. Bioglass® additions led to the formation of a complex calcium phosphate silicate which hampered the reinforcement process. The fracture toughness of the hydroxyapatite-glass composites was shown to be within the 1.1–1.2 MPam1/2 range, which is double that determined for sintered hydroxyapatite. A 2 m thick apatite layer was observed on the surface of the hydroxyapatite-glass composites after 48 h immersion in a simulated human blood plasma, whereas only a few apatite crystals were detected on sintered hydroxyapatite after 7 days immersion. From the results obtained we anticipate that the composites might show a higher rate of bone bonding, leading to enhanced bioactivity. |
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