Plaque removed from subjects in a 1-ppm fluoride area was incubated in vitro with sucrose solutions. Following the pH decrease caused by fermentation, the fluid phase obtained by centrifugation contained free fluoride ions. The fluoride ion activity of the fluid phase increased when the pH decreased; the relationship was linear. The amount of fluoride ions in the fluid phase was positively associated with the ratio fluid phase/amount of plaque. The fluoride ion activity of the plaque appears to be related to the solubility of plaque components at the pH of the plaque. Incubation of plaque in saline, however, indicated that at pH 6 most of the fluoride in plaque is bound.
展开▼
