| Abstract: | The influence of dodecylamine hydrochloride (DAC) on the dissolution rate behavior of hydroxyapatite (HAP) samples prepared by digestion at 100°C and heated to various temperatures was investigated. The dissolution rates of HAP samples heated to temperatures of 300, 500, 750, 900, 1000, and 1200°C were determined at various levels of DAC in an acetate buffer having a pH of 4.50 and an ionic strength of 0.10. DAC adsorption isotherms for these different HAP samples and the specific surface areas were also determined. The initial dissolution rates (IDR) for all preparations generally decreased with increasing DAC levels with an approximately inverse relationship between IDR and DAC adsorption. For HAP samples heated at 1000°C and higher, the dissolution rates at 3.0 mM DAC were completely inhibited, while for samples heated at 900°C or less, there was a significant residual IDR at 3.0 mM DAC. This residual rate was approximately 20% of the zero DAC rate for all samples treated between 300 and 900°C. These results are in agreement with the concept that HAP prepared by precipitation and digestion at 100°C has two or more kinds of sites for dissolution and that heat treatment at around 1000°C or greater causes the elimination of one or more of these sites. |
