The effects of electrolytes on the rates of hydroxyapatite (HAp) formation at 25 and 38°C were investigated. Solutions were selected to contain ions in common with HAP lattice ions or to contain ions capable of substituting into HAP. The effects of phosphate, calcium, chloride, and fluoride were stu
Phase evolution during the formation of stoichiometric hydroxyapatite at 37.4 °C
✍ Scribed by Yaser E. Greish; Paul W. Brown
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 112 KB
- Volume
- 67B
- Category
- Article
- ISSN
- 1552-4973
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✦ Synopsis
Abstract
The mechanism of formation of stoichiometric hydroxyapatite in aqueous solution by the acid–base reaction of the precursor calcium phosphates tetracalcium phosphate [Ca~4~(PO~4~)~2~O, TetCP] and anhydrous dicalcium phosphate (CaHPO~4~, DCPA) was investigated. Phase evolution during the formation of hydroxyapatite was studied, and could be correlated with the kinetics of reaction. Initial dissolution of precursors is followed by hydroxyapatite nucleation and growth. Consumption of DCPA precedes that of TetCP and results in the formation of nonstoichiometric hydroxyapatite. As a result of continued TetCP dissolution, the pH of the solution increases towards a pH at which hydroxyapatite and Ca(OH)~2~ co‐exist in equilibrium. Hydroxyapatite formation takes place in two stages: initially formed, nonstoichiometric hydroxyapatite subsequently reacts with TetCP and is converted to stoichiometric hydroxyapatite. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 67B: 632–637, 2003
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