Effect of in vitro acidification on plaque fluid composition with and without a NaF or a controlled-release fluoride rinse

Plaque fluid ion concentration changes, especially fluoride, in response to the pH decrease associated with a cariogenic episode are important compone nts of the caries process. A "controlled-release" (CR) fluoride rinse, base d on the controlled release of fluoride in the presence of calcium, has bee n shown to form large fluoride reservoirs in resting plaque. In this study, the in vitro acid-induced release of fluoride, and other ions, was examine d in 48-hour-fasted plaque fluid from subjects (n = 11) who received no rin se, or who used a 228-ppm CR or NaF fluoride rinse 1 hr before being sample d. After collection, the plaque was centrifuged to yield plaque fluid, acid ified (0.1 mu L of 0.5 mol/L HCl per milligram plaque), and then re-centrif uged before a second sample was obtained. Although previous studies indicat ed a higher plaque fluid fluoride after the new rinse relative to NaF, no s tatistically significant difference was observed here. Average fluoride rel ease after acidification (average pH, 5.2) was statistically greater follow ing the use of the CR rinse (153 mu mol/L) compared with the NaF rinse (17 mu mol/L). No fluoride release was seen in the no-rinse samples. The pH, Fr ee calcium, phosphate, acetate, propionate, and buffer capacity were not af fected by the different amounts of fluoride deposited in the plaque. Howeve r, following acid addition, an increase in free calcium and phosphate was o bserved, which was also independent of the rinse. The large release of fluo ride following acidification suggests that the new rinse may provide an imp roved cariostatic effect.