Hydroxyapatite and Fluoroapatite Behavior with pH Change


Loai Aljerf1), Ala Eldin Choukaife2)


Background: Due to the topical fluoride treatment, fluorapatite (FAp) and calcium fluoride are forming on a dental enamel surface. Different researches concerned in oral biology, prevention and treatment have studied hydroxyapatite (HAp) and FAp dissolution in addition to precipitation reactions since these materials are essentials in dental hard tissues. However, FAp is less soluble phase amongst the calcium phosphates and has more complicated equilibria. Objective: This study has indicated the solubility isotherms, S of CaF2 and the solubility of FAp and HAp using the titration method.Design: In this study, a titration with pH adjustment method using diode laser-scattering system had been performed to
monitor any solid increment addition where the material has been reprecipitated and detected by the endpoint represented by the output signal. Materials and Methods: The composition and the morphology of the precipitate were studied and the Ca/P ratio was also determined. In addition, a comparative study of the solubility isotherm of the CaF2, HAp, and FAp were performed among wax-coated apparatus and an uncoated vessel experiment. Results: The results showed that Ca/P ratio of the precipitate has decreased steadily at lowering pH values. In addition, FAp has shown slightly less solubility than HAp at pH < 3.9 and the particles were single crystal with rod-like morphology at pH 4.1
and polycrystalline at pH < 3.6. Conclusion: Wax-coated apparatus helped to avoid any expected interferences, the titration was successfully validated, while solutions rich with fluoride were acted as modifying agents to the solubility of HAp..


biocorrosion, complicated equilibria, particles, phase, topical fluoride

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