Crystallographic nature of fluoride in enameloids of fish.
X-ray diffraction studies on calcified tissues (teeth and/or scales) of fish and of shark showed that the presence of fluoride affects the crystallite size and lattice parameters of the apatite phase. An inverse correlation between F contents (ranging from 0.2 to 3.8 wt% F) and alpha-axis dimensions (9.441 to 9.375 +/- 0.003 A) exists for both synthetic and enameloid apatites and is consistent with the F-for-OH substitution in the apatite, idealized as Ca10(PO4)6(OH)2 and Ca10(PO4)6F2, for fluoride-free and maximum fluoride-substituted apatite, respectively. In synthetic systems, the incorporation of F is found to be dependent on the F concentration of the media from which the apatite formed. This dependency is also observed between F content of the dentine apatites and the F concentration of the water from which the fish can (i.e., less than 0.08 ppmF in fresh water, about 1.3 ppm in seawater). However, no such dependency was observed between the F incorporation in fish enameloid apatite and the F concentration in the water of origin. In some cases, the F incorporated in the enameloid apatite is much in excess of what can be expected from the F concentration of water. These observations suggest that in some fish, a fluoride-concentrating mechanism is operative during the formation of the enameloid but not during the formation of the dentine, and this mechanism appears to be specie-related.
D000818:Animals; D001031:Apatites / Q000032:analysis; D002347:Carps; D003743:Dental Enamel / Q000032:analysis*; D003804:Dentin / Q000032:analysis*; D005399:Fishes; D005459:Fluorides / Q000032:analysis*; D008968:Molecular Conformation; D012754:Sharks; D013045:Species Specificity; D013055:Spectrophotometry, Infrared; D014961:X-Ray Diffraction
D001031:Apatites; D005459:Fluorides