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Journal of Dental Research, Vol 67, 1493-1498, Copyright © 1988 by International & American Associations for Dental Research Online Journals
ARTICLES |
J. A. Budz, M. Lo Re and G. H. Nancollas
Chemistry Department, State University of New York, Buffalo 14214.
The kinetics of dissolution of hydroxyapatite (HAP) and human enamel (HE) powders in lactate buffers was investigated by means of a Constant Composition technique. The rates were interpreted in terms of a surface-controlled dissolution mechanism. It was shown that the overall dissolution of both HAP and HE crystallites in lactate buffers resulted from an interplay of the calcium chelating action of lactate ion, its interaction with surface calcium sites, and the retardation effects of both ionized (L-) and un-ionized (HL) lactic acid due to adsorption at phosphate surface sites. The presence of lactate in demineralizing solutions also influenced the "acquired crystallite resistance" for dissolution, and the rates decreased as the reaction proceeded. The influence of surface protective agents [methanehydroxydiphosphonate (MHDP) and polyacrylic acid (PAA)] on HAP and HE dissolution rates was also extensively studied in partially saturated lactate buffer (0.05 mol L-1). Although the overall kinetic effects of both additives appeared to be similar, there were considerable mechanistic differences. MHDP might interact with lactate by competition for surface calcium sites. In contrast, PAA appeared to act independently of lactate under the experimental condition used. This would tend to support the recommendation of White (1987), that PAA was more suitable as a surface protective agent for artificial caries lesion preparation.
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H.C. Margolis, Y.P. Zhang, C.Y. Lee, R.L. Kent JR, and E.C. Moreno Kinetics of Enamel Demineralization in vitro Journal of Dental Research, July 1, 1999; 78(7): 1326 - 1335. [Abstract] [PDF] |
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