Long-term (8 days) effects of exposure to low concentrations of fluoride on enamel formation in hamster tooth-germs in organ culture in vitro.
Second maxillary molars of 3-4-day-old hamsters were cultured for 7-8 days in the continuous presence of fluoride (F-) or chloride in concentrations between 2.63 microM and 1.31 mM. For biochemical study, explants were labelled during the last 24 h of culture with a triple label of [3H]-proline, 45Ca and 32PO4. The 3H-labelled presumptive amelogenins were separated from the 3H-labelled dentine collagens by a three-step extraction procedure. Histologically, chronic exposure to F- had no obvious effects below 26.3 microM; at 26.3 microM of F-, a non-mineralizing enamel matrix was observed besides that of a normal mineralizing enamel. From 52 microM of F- onwards, only a non-mineralizing enamel matrix was found in decreasing amounts extracellularly as F- concentrations increased. Except for the presence of globular dentine, dentinogenesis was not obviously affected by F-. Biochemically, total synthesis of presumptive amelogenins was hardly disturbed, but their solubility was changed by chronic F- treatment; more amelogenins became formic-acid soluble at the expense of water-soluble amelogenins. Chronic exposure to F- decreased the water-soluble amelogenin fraction according to a logarithmic function of the medium F- concentration. By extrapolation, it was calculated that concentrations higher than 1-2 microM of F- affect amelogenesis in vitro. Synthesis of dentine collagen was not affected by chronic exposure to F- in vitro. Chronic exposure to F- decreased uptake of 45Ca and to a less extent trichloroacetic acid-soluble 32PO4. Chronic F- exposure may inhibit energy production in the enamel organ resulting in an impairment of enamel matrix secretion as well as that of a trans-epithelial transport mechanism for calcium.
D000566:Amelogenesis / Q000187:drug effects*; D000818:Animals; D006224:Cricetinae; D003743:Dental Enamel / Q000378:metabolism; D003746:Dental Enamel Proteins / Q000096:biosynthesis; D005109:Extracellular Matrix / Q000378:metabolism; D008647:Mesocricetus; D008963:Molar / Q000473:pathology; D009924:Organ Culture Techniques; D012969:Sodium Fluoride / Q000494:pharmacology*; D014083:Tooth Germ / Q000187:drug effects* / Q000473:pathology
D003746:Dental Enamel Proteins; D012969:Sodium Fluoride