PubMed · 6582704
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K G König. 1983-09-16. [Prevention programs for dental practice].. https://pubmed.ncbi.nlm.nih.gov/6582704/
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Because of suggestions that food is a rich source of fluoride to humans and the absence of permissible and upper limits of fluoride for irrigation water, plant uptake studies were conducted using fluoride-rich irrigation water. Ladyfinger was grown in sand and soil cultures for 18 wk and the accumulation of fluoride in various plant parts was studied. The potential for ingestion of fluoride by humans through this route was also considered. The percentage uptake was greater in sand-cultured plants than in soil-cultured plants. The root accumulates most of the fluoride supplied through irrigation water and the fruit accumulates the least. Up to 120 mg fluoride/litre of irrigation water did not harm the plants. The ingestion of fluoride by humans from plants irrigated with water containing 10 mg fluoride/litre would be 0.20 mg per 100 g ladyfinger.
Fluoridated hydroxyapatites were synthesized with two different modes of fluoride supply: by supplying F(-)-free solution initially, followed by a F(-)-containing solution whose fluoride concentration was stoichiometrically equal to that of fluorapatite; and with the order of supply of these solutions reversed. Both of these heterogeneously synthesized fluoridated hydroxyapatites showed typical calcium phosphate X-ray diffraction patterns; and both had similar total fluoride contents (0.94 +/- 0.02 and 0.99 +/- 0.03 mmol/g, respectively), i.e. half of the maximum fluoride content of fluorapatite. However, they differed considerably in their physico-chemical properties. The former had a wider peak breadth of X-ray diffraction and a lower apparent solubility (Ca = 12.2 +/- 0.7 mmol/l) than the latter (Ca = 19.8 +/- 0.4 mmol/l) at 37 degrees C and pH 4.0. Wavelength dispersive spectroscopy attached to scanning electron microscopy gave clearly different spectra. Electron spectroscopy for chemical analysis of apatite pellets made by pressing and heating showed a slightly larger F1s signal at the crystal surface of the former, although the difference was not marked. These results suggest that two different types of heterogeneous fluoridated hydroxyapatites were formed, hydroxyapatite covered with fluorapatite and fluorapatite covered with hydroxyapatite.