SHORT-TERM EFFECTS OF FLUORIDE ON BIOSYNTHESIS OF ENAMEL-MATRIX PROTEINS AND DENTIN COLLAGENS AND ON MINERALIZATION DURING HAMSTER TOOTH-GERM DEVELOPMENT IN ORGAN-CULTURE

The effect of various concentrations of fluoride (F-) on cell proliferation, matrix formation and mineralization was examined in hamster molar tooth germs in premineralizing and mineralizing stages. The exposure lasted 16 h (mineralizing stages) and 24 h (premineralizaing stages) and the F- levels ranged from 2.63 .mu.M to 2.63 mM; [3H]-thymidine, [3H]-proline, 45Ca and 32PO4 were used as markers for cell proliferation, matrix formation and mineralization, respectively. The proline-labeled amelogenins were isolated by sequential extraction with water and formic acid and their nature examined by SDS[sodium dodecyl sulfate]-urea-polyacrylamide electrophoresis. Digestion by collagenase was used to assess the amount of proline incorporated into collagens. F- in concentrations up to 1.32 mM inhibited neither biosynthesis of DNA and amelogenins, nor synthesis of collagens and their hydroxylation. Amelogenins extracted from F- induced, non-mineralizing enamel matrix had the same electrophoretic mobility and the same degree of phosphorylation as amelogenins from normal, mineralizing enamel. F- increased the uptake of 45Ca and TCA[trichloroacetic acid]-soluble 32P dose-dependently, starting with 52 .mu.M. Thus, interference with secretion of enamel matrix by F- takes place at much lower concentrations than required to inhibit biosynthesis of enamel matrix.