Nuclear magnetic resonance investigation of fluoride ions in hydroxyapatite

Morphogenesis and Structure of Human Teeth in Relation to Biomimetically Grown Fluorapatite−Gelatine Composites

“…Pure fluoroapatite is hexagonal because the fluoride ions are located exactly within the plane of the calcium triangles. , Fluorapatite and hydroxyapatite form continuous solid solutions. In the case of mixed occupation of the channel positions, that is, the apatite contains OH - as well as F - , the fluoride ions can be displaced from the center of gravity by about 1 pm because of the formation of OH−F hydrogen bonds. , Figure shows three different arrangements of the column ions in apatites, which contain both fluoride and hydroxide 7 Different arrangements of OH - and F - ions in the channels of apatite.…”

“…In the case of mixed occupation of the channel positions, that is, the apatite contains OHas well as F -, the fluoride ions can be displaced from the center of gravity by about 1 pm because of the formation of OH-F hydrogen bonds. 45,46 Figure 7 shows three different arrangements of the column ions in apatites, which contain both fluoride and hydroxide. 47 In human teeth, the composition of apatite is different from the prototypes because its constituents can be replaced by a number of ions; for example, in tooth enamel more than 30 elements have been detected, and calcium is partly substituted by sodium, potassium, and other cations.…”

Synthesis in Pure Ethanol and Characterization of Nanosized Calcium Phosphate Fluoroapatite

“…Hydroxyapatite easily forms solid solutions with fluoroapatite [Ca 10 (PO 4 ) 6 F 2 ; FAP] because these two compounds are crystallized in a hexagonal system and their lattice parameters are similar. , Hydroxyl- and fluoroapatite are also characterized by the presence of channels parallel to the c axis where HO - and F - ions (two for each unit cell) are localized − It has been established by IR and NMR spectroscopies , that FHAP is stabilized by a hydrogen bond between hydroxide and fluorine ions which forms −O−H−F− chains along the channel of the apatitic structure. Therefore, the FHAP solid solutions show very high thermodynamic stability and very low solubility in water. , …”

The Fluoridation of Nonstoichiometric Calcium Hydroxyapatite. An Infrared Study

“…Indeed, there is evidence from 19F n.m.r. studies of mineral hydroxyapatite containing small quantities of fluoride to suggest that configurations of the type O-H...F...H-O occur along the c-axis of the crystal (13,19). In this case, three O-H...O bonds would be broken and one of their hydroxyl groups inverted by partial fluoridation of an otherwise ordered column in the apatite lattice.…”