Journal of Dental Research, Vol 75, 1019-1026, Copyright © 1996 by International & American Associations for Dental Research Online Journals
Constant composition dissolution kinetics studies of human dentin
E. P. Paschalis, J. Tan and G. H. Nancollas
Department of Chemistry, State University of New York at Buffalo, New York 14260, USA.
The constant composition (CC) method has been used to study the dissolution
kinetics of whole powdered human dentin as a function of calcium phosphate
concentration at relative undersaturations with respect to hydroxyapatite
(sigma HAP), ranging from +0.8 to -2.8, ionic strength from 0.05 to 0.30
mol/L-1 in sodium chloride or potassium nitrate, pH 4.00 to 5.50, and molar
calcium/phosphate ratio in the reaction solutions from 0.05 to 11.1. The
results suggest that human dentin behaves as a mixture of at least two
calcium phosphate phases, HAP-like and octacalcium phosphate-like,
OCP-like. Significant dissolution took place in solutions that were even
supersaturated with respect to HAP, and the rates exhibited a striking
insensitivity to relative undersaturation, while influenced by ionic
strength, pH, and molar calcium/phosphate ratio in the reaction solutions.
Although the dissolution was retarded in the presence of magnesium ion, the
reaction rate showed the same insensitivity to undersaturation with respect
to calcium phosphate.
