ISSN:
0021-9304
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
,
Technology
Notes:
Calcium phosphate (Ca, P) precipitation behavior on the surface of two bioactive glasses and four bioactive glass composites - two with hydroxylapatite (Ca10(PO4)6(OH)2) and two with rhenanite (CaNaPO4) - were studied in simulated body fluid (SBF) and in Tris-Buffer at 5, 8, 16, 24, 48, 72, and 144 h. The Weight loss of the materials was measured and the amount of precipitation was estimated using scanning electron microscopy with electrochemical detection (SEM-EDX) analysis. The test was repeated for one glass and its respective rhenanite composite every 3 h until 60 h and thereafter every 10 h until 150 h in SBF. Atomic absorption spectroscopy, spectrophotometry, SEM-EDX analysis, and pH measurements were performed on these samples. It is shown that in vitro the composite materials have a higher capacity for Ca, P precipitation than the glasses. Weight losses of the materials correlate well with their composition. Both the glass and Ca, P phases influence the precipitation mechanism and rate. Precipitation begins preferably from the glass phase. Ca, P particles clearly influence the time of onset and rate of precipitation. Cross-sectional EDX analysis of the samples revealed an absence of a clear Sirich layer in glass AOBO (SiO2 53.9 mol %, Na2O 27.5, CaO 12.4, P2O5 6.2, Al2O3 0.0 and B2O3 0.0) composites. This was attributed to the presence of extra calcium and phosphate ions on the surface of the material. The ion-concentration and pH change curves offered insight into the mechanism of precipitation. A connection was established between SEM-EDX results and the release curves. Formation of an Si, Ca, Na film was observed that seemed to initiate the Ca, P precipitation. It is speculated that it is a characteristic of this particular glass composition. Two possible models for the mechanism of Ca, P precipitation are discussed. Phosphate polycondensation with silicate network or Ca binding to silicate network can both explain the results and it is assumed that in general both mechanisms play a role in the precipitation process. © 1993 John Wiley & Sons, Inc.
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jbm.820271003
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