Effect of a water rinse on 'labile' fluoride and ether ions in plaque and saliva before and after conventional and experimental fluoride rinses

Labile reservoirs are important in maintaining ion concentrations in oral f luids, especially after a fluoride dentifrice application, where a persiste nt increase in fluid fluoride can mitigate or reverse caries progression. I n this study, the effect of experimental and conventional fluoride rinses o n the in vitro and in vivo water-induced release of fluoride, calcium, phos phate, acetate and hydrogen ions from oral reservoirs was examined. At the start of each experiment, 13 subjects rinsed either with a conventional 228 -ppm fluoride NaF rinse, a 228-ppm fluoride controlled-release rinse (CR ri nse) or received no rinse. Sixty minutes later upper and Tower molar plaque samples and 1-min saliva samples were collected. The subjects then rinsed with deionized water for 1 min, and 7 min later, a second set of samples wa s collected (in vivo study). Plaque fluid and clarified saliva were then re covered from samples by centrifugation, and the remaining plaque mass was s equentially extracted with water and acid to measure the water-extracted an d total whole-plaque fluoride (in vitro study). All the samples were analyz ed using microtechniques for pH, free calcium, phosphate, organic acids (pl aque fluid) and fluoride (plaque fluid, centrifuged saliva and plaque extra cts). Results showed that in vivo water rinsing decreased acetate and phosp hate in plaque fluid, and fluoride in plaque fluid and saliva, but had no e ffect on plaque fluid pH. In vivo water rinsing, however, increased plaque fluid free calcium, apparently due to water-induced loss of calcium-binding ions. Water- or fluoride-rinse-induced changes in plaque fluid concentrati on were greater at the lower molar site, suggesting that rinse pooling may influence ion distribution. Before the water rinse, plaque fluid, saliva an d whole-plaque total fluoride values were 1.7, 2 and 4 times higher after t he CR rinse compared to the NaF rinse. Furthermore, the CR rinse deposited approximately 11 times more water-extracted fluoride compared to the NaF ri nse, suggesting a 'more efficient' precipitation of 'labile' or 'loosely bo und fluoride'. The results presented here, and in previous studies, suggest the possibility of formulating effective fluoride dentifrices with a lower fluoride content than is currently in use. Copyright (C) 2001 S. Karger AG . Basel.