Changes in the Salivary Fluoride Concentration after Adding Low-concentrated Fluoride

Objective:

The aim of this study was to investigate the changes in the fluoride (F) concentration in saliva after adding low-concentrated F, and to determine the influence of protein (mucin and albumin) and calcium in the saliva on the concentration of low level F.

Method:

A flow injection analysis (FIA) instrument was used to determine the F ion concentrations in saliva. FIA can determine the F in a sample solution at a concentration as low as 0.005 ppm (5μg/L). A standardized solution (0.01, 0.05, 0.5ppm F) was added to the saliva at a rate of 1:9, and then the temporal changes in the F ionic level were measured. The change in the F concentration after the addition of F was determined as the increase in the F concentration from the original salivary F concentration. Similarly, F standard solution (0.5ppm) was added to a protein solution (mucin or albumin, 3%) and a calcium solution (1.25mg/100ml), and then the changes in the F concentration were again examined. Both ANOVA and t-tests were used to compare the F concentrations.

Result:

The F ion concentration in the saliva that contained the additional F showed a decrease of 17-45% in comparison to the F ion concentration of purified water that contained F.  When F was added to mucin, albumin and calcium, there were 18.6, 15.7, and 34.6% reductions in the concentration, respectively. In addition, the concentration of F in mucin+ calcium and albumin+calcium was found to have decreased by 62.1 and 44.8%, respectively.

Conclusion:

The mixture with a solution of calcium and protein led to a higher rate of decline in the F concentration than the sum of the decline rate of each solution independently. These results suggested that there is a synergistic effect of protein and calcium on the low F concentration in saliva.