Mechanisms of Enamel Dissolution in Acid Buffers.

A quantitative understanding of the mechanism of human dental enamel dissolution in buffers is important because it should lead to a clear description of the causative factors in caries formation, and it can be profitably employed in the design of meaningful screening methods for potential anti-decay agents. Gray' has reported studies on enamel dissolution, concluding that the rates of dissolution of enamel in his buffers were controlled by the diffusion rates of the reactants and products of the dissolution reaction. He also pointed out that the initial enamel dissolution rate is largely a function of the total buffer concentration, buffer acid strength, and pH. The effects of common and foreign ions on the rates of enamel dissolution were accounted for in a consistent fashion. Gray deduced a semi-empirical equation for the rate of dissolution which rather satisfactorily describes all the experimental findings. This relationship includes the bufferacid dissociation constant, the total buffer concentration, the hydrogen-ion concentration, and other terms, when necessary, for common and foreign ions affecting the rate. The success of this equation suggested that detailed mathematical models could be formulated and tested, employing simultaneous diffusion and chemical reaction, as has been done in describing the dissolution behavior of benzoic acid2 in basic and buffered media. The present communication is a report on the study of two such models. These have been examined with Gray's data. The analyses demonstrate the usefulness of this approach in future studies on dental problems.