DISTRIBUTION AND METABOLIC EFFECTS OF HUMAN PLAQUE FLUORINE

It has been shown by the fluoride electrode, by the liver esterase and colorimetric methods and by dialysis, that only about 2-3 per cent of the total fluorine of plaque detectable by chemical methods is present as free ions. There was no evidence of fluoride binding by plaque matrix or that the fluorine was present as insoluble inorganic salts. Plaque bacteria cultured on media containing fluoride contained high concentrations of fluorine and showed less capacity for acid production than controls, suggesting that the stored fluorine was active as an inhibitor. It is concluded that a high proportion of plaque fluorine is contained within the bacteria. Acid production was measured in vitro in plaque from children from towns with 0, 1.0 and 1.8 ppm F in the water. The results showed a smaller pH fall in the plaque from the fluoride areas which was highly significant with 1.8 ppm and of borderline significance with 1 ppm. It is likely that acid production was affected directly by the higher fluorine of the plaque but the possible indirect effect of lower caries incidence in the fluoride areas on plaque metabolism cannot be disregarded. © 1969.