Abstract
Solubility and remineralization behaviors of self-setting apatite cement were investigated in organic acids of acetic, lactic, and citric acid and in synthetic saliva.The degree of supersaturation of the synthetic saliva used here was comparable to that of resting human saliva.One-week solubility of several types of self-setting appatite cement was considerably amaller than that of commercially available dental cements in the organic acids.For example, the one-week solubility of the self-setting apatite cements in citric acid, one of the most powerful acids in dissolving cements, was less than 4.5%.Thermodynamic analysis by use of chemical potential plots suggested that the solution composition was in equilibrium with dicalcium phosphate dihydrate, which probably formed on the surface.Thus no further dissolution occurred.This finding can partially account for the smaller solubility of the present cements even in the organic acids studied here.In synthetic saliva, the solution phoshphate decreased with time once the set cement was introduced to the solution, whereas the solution calcium increased.The former finding suggests that some phosphate compounds precipitated in the synthetic saliva and the latter finding indicates that some portion of the set cement dissolved.The thermodynamic analysis of the solution compositions, however, strongly suggests that remineralization is major process and dissolution a minor one.In fact, comparison of scanning electron micrographs of the cement pellets before and after the treatment in synthetic saliva showed that smaller crystals of apatite deposited on the surface of the cement pellet after the treatment in synthetic saliva.This finding comfirms that in oral environment the present cements remineralizes to take lattice nios present in oral fluids i.e.saliva, in its solid structure.
