CHARACTERIZATION OF ENAMEL SURFACE DEMINERALIZATION, REMINERALIZATION, AND ASSOCIATED HARDNESS CHANGES IN HUMAN AND BOVINE MATERIAL

Enamel demineralization and remineralization were investigated in relation to change of surface microhardness. Within the investigated range of 120 hardness units from the initial, mineral loss or gain were reflected in parallel, linear changes of microhardness. Changes of one hardness unit corresponded to about 0.04 μ moles of Ca2+/cm2 of test surface. The molar Ca P ratio was 1.65 for both the demineralization as well as the remineralization process; this result indicated a stoichiometric dissolution and redeposition of hydroxyapatite in the enamel. On the basis of calculations of indenter penetration, softened enamel was shown to have gradients of mineral density from the surface inwards depending upon the demineralization method. The softening and rehardening were shown to take place in the outer 5 μ of enamel surface. The acid resistance of the rehardened enamel was similar to that of the original. © 1969.