"The reason might be the fluoroapatite
and the revolving set of teeth which is always immersed in sea water," said Prof Epple.
Figure 10 indicates that the intensity of the calcite and fluoroapatite
peaks decrease with the increase of concentrations of HN[O.sub.3].
slow conversion of fluoroaluminium complexes to insoluble species, such as gibbsite [Al[(OH).sub.3]], and possible precipitation of fluorite (Ca[F.sub.2]) or fluoroapatite
[[Ca.sub.5](PO4)3F], has been suggested in soils amended with Al or Ca (Rai et al.
However, the hydroxide group can be replaced by fluoride to form a calcium fluorophosphate (fluoroapatite
) and it is this which makes the teeth less prone to acid attack and more resistant to dental caries.
(From Lindsay, 1979) Mineral Formula Fluoroapatite
[Ca.sub.5][(P[O.sub.4]).sub.3]F Hydroxyapatite [Ca.sub.5][(P[O.sub.4]).sub.3]OH Tricalcium phosphate [Ca.sub.3][(P[O.sub.4]).sub.2] Strengite FeP[O.sub.4]-2[H.sub.2]O Variscite AIP[O.sub.4]-2[H.sub.2]O Mineral Solubility Product (M) Fluoroapatite
[10.sup.-59] Hydroxyapatite [10.sup.-57] Tricalcium phosphate [10.sup.-26] Strengite [10.sup.-26] Variscite [10.sup.-21] TABLE 10-5 Active S reservoirs.