Effect of Fluoride on the Growth of Hydroxyapatite and Human Dental Enamel

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Abstract
A highly reproducible seeded growth method was used to study the mineralization of calcium phosphate on human enamel and hydroxyapatite seed crystals at a pH of 7.4 and at 37.degree. C in stable supersaturated solutions of calcium phosphate containing various F- [anticaries agent] concentrations. The pH and pF values were maintained constant potentiometrically by the addition of KOH and KF, respectively, and the grown material was characterized chemically, by IR spectroscopy, by scanning electron microscopy and by subsequent dissolution kinetic experiments. Low F- concentrations (.apprx. 0.15 ppm) reduce the crystallization rate in the initial stages, but calcium phosphate mineralization enhancement is observed in the presence of higher-F- concentrations (1-5 ppm). Whereas the stoichiometry of the 1st-formed surface phase corresponds to that of octacalcium phosphate in the absence of F-, higher molar calcium phosphate ratios are indicated in its presence.