FLUORIDATION OF HYDROXYAPATITE POWDER BY AMMONIUM HEXAFLUOROSILICATE

Diamine silver fluoride [AgF: (NH3)(2)AgF] is a unique fluoride soluti on used clinically in Japan for primary teeth. AgF has been shown to r educe dental caries and dentine hypersensitivity. However, AgF also st ains teeth black due to sulfide precipitation and thus is unacceptable for permanent teeth. In the present study, the potential value of amm onium hexafluorosilicate [SiF: (NH4)(2)SiF6], which has a formula simi lar to that of AgF but contains no Ag, was studied with respect to its ability to fluoridate apatite. Hydroxyapatite [HAP: Ca-10(PO4)(6)(OH) (2)] powder was treated with several topical fluoride solutions, i.e. neutral sodium fluoride, acidulated phosphate fluoride (APF) along wit h AgF and SIE Following treatment, the HAP powders were analyzed for t heir fluorine content, crystallinity changes, and solubility in acidic solution. The highest level of fluoridated HAP [FA9: Ca-10(PO4)(6)(OH )(x)F-2-x] was observed in HAP powder treated with SIF, even though mo re total fluorine in the form of FAP and CaF2 was observed in HAP powd er samples treated with APE Presumably as a consequence of this higher level of FAP formation after SIF treatment, the highest level of crys tallinity along with the lowest solubility in acidic solution were obs erved in HAP powder treated with SiF solution. We concluded, therefore , that SiF may have potential value for use as a topical fluoride solu tion.