The retardation of enamel dissolution rates by adsorbed long-chain ammonium chlorides.

Dissolution rate studies were conducted with hydroxyapatite and enamel in the presence of adsorbed surfactants. In general, the ability of the surfactant to retard the dissolution rate was directly related to its ability to adsorb onto apatite. Cetylpyridinium chloride adsorbed poorly onto apatite, and its influence on the dissolution rate was marginal. The long-chain protonated amines were much more effective as rate retarding agents, sometimes of the order of 1,000-, to 10,000-fold. These compounds were also found to adsorb much more strongly. A systematic dependence of the dissolution rate on chain length was found for these amines.