title: Stoichiometry of fluoride release from fluorhydroxyapatite during acid dissolution.
abstract: Release of F from fluorhydroxyapatite (FHAp) during acid dissolution was studied to validate the use of this mineral as a plaque reservoir of F. FHAp minerals having a wide range of F concentrations were synthesised by aqueous precipitation, and samples repeatedly exposed to 50 mM lactic acid solution, pH 4.5, or similar lactic/acetic/formic acid mixtures, until dissolution was complete. While the Ca/P ratio in solution remained relatively constant and close to the ratio in the solid, the solution F/Ca ratio invariably changed during dissolution. During initial stages the F/Ca solution ratio was lower than in the solid but rose to reach a plateau higher than in the solid as dissolution progressed, an effect that was more pronounced with low-F FHAp. With these minerals the plateau F/Ca level never reached 0.2, suggesting that a F-enriched FHAp rather than pure fluorapatite precipitates during dissolution. It is concluded that a high-F FHAp mineral would best serve as an apatitic plaque reservoir of F.
authors.affiliation: Dental Research Unit, Health Research Council of NZ, Wellington.
authors.forename: E I
authors.initials: EI
authors.lastname: Pearce
authors.forename: N
authors.initials: N
authors.lastname: Guha-Chowdhury
authors.forename: Y
authors.initials: Y
authors.lastname: Iwami
authors.forename: T W
authors.initials: TW
authors.lastname: Cutress
mesh_terms: D000085:Acetates / Q000737:chemistry; D000143:Acids / Q000737:chemistry; D001031:Apatites / Q000032:analysis / Q000737:chemistry; D002118:Calcium / Q000032:analysis; D011232:Chemical Precipitation; D003773:Dental Plaque / Q000737:chemistry; D005459:Fluorides / Q000032:analysis / Q000737:chemistry*; D005561:Formates / Q000737:chemistry; D006801:Humans; D006882:Hydroxyapatites / Q000032:analysis / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000032:analysis / Q000737:chemistry*; D007773:Lactates / Q000737:chemistry; D019344:Lactic Acid; D010758:Phosphorus / Q000032:analysis; D012995:Solubility
chemical_list: D000085:Acetates; D000143:Acids; D001031:Apatites; D005561:Formates; D006882:Hydroxyapatites; D007773:Lactates; C030544:formic acid; D010758:Phosphorus; D017665:Hydroxyl Radical; D019344:Lactic Acid; C028869:fluor-hydroxylapatite; C025105:fluorapatite; D005459:Fluorides; D002118:Calcium