Ali Nemati; Abdorreza Sheikh Mehdi Mesgar; Fathollah Moztarzadeh
Volume 3, Issue 2 , June 2009, , Pages 135-149
Abstract
In this paper, dissolution kinetics of Amorphous Calcium Phosphate as well as cements in the Simulated Osteoclastic Medium (SOM) was evaluated based on the Shrinking Core models considering the liquid-solid reactions. Based on this model, three steps may be considered as controlling steps in the system: ...
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In this paper, dissolution kinetics of Amorphous Calcium Phosphate as well as cements in the Simulated Osteoclastic Medium (SOM) was evaluated based on the Shrinking Core models considering the liquid-solid reactions. Based on this model, three steps may be considered as controlling steps in the system: diffusion of component A through the surrounding films, reaction of component A with solid on the surface and diffusion through the interface. Two cases were considered here: 1. Shrinking Core model with formation of the intermediate phase 2. Shrinking Core model without formation of the intermediate phase Then, experimental data were used for the evaluation of the controlling steps and its mechanism (s). The results showed that enough amounts of calcium were entered into the solution in the initial stage of the process. This in turn causes to form a film on the particles, and the potential of calcium carbonate complex, resulted in the reduction of calcium saturation in the system. The amounts of entered calcium into the solution were higher in the amorphous system. In other words, a longer time is required in the crystalline system for more entrance of calcium into the solution (as in the sample H1T). Based on these observations, it was concluded that the approximately crystalline cements with carbonate falls between the crystalline cements without carbonate and amorphous system (The amounts of entered calcium into the solution). Dissolution rate of ACCPs in the Simulated Osteoclastic Medium (SOM) was dependent on the contents of carbonate and remaining water. Dissolution behavior in the SOM showed that the behavior of ACCP (high carbonate)–DCPD–PHA–Gelatin system was comparable to the ACCP (low carbonate)-DCPD. The presence of PHA and gelatin in cement system decreased the dissolution rate. The dissolution kinetics of the cements and ACCPs in the SOM was likely controlled by the formation of an acid-resisting ACP and/or DCPD as product layer.
