Mechanisms of inhibition of enamel demineralization by fluoride dentifrices

The anticaries efficiency of fluoride (F) dentifrice is well established, but the relative importance of F in dental plaque or on enamel on the inhibition of enamel demineralization is unknown. Objective: To evaluate the relationship between F in dental plaque or formed on enamel due to F dentifrice use as source of F to plaque fluid and the subsequent inhibition of enamel demineralization. Methods: A short-term, double-blind and crossover in situ study was conducted. To evaluate the effect of F in plaque, 12 volunteers brushed their teeth with no F (NF) or fluoridated (FD; 1,100 µg F/g, NaF) dentifrices, and started wearing a palatal appliance containing enamel blocks covered with a test plaque from S. mutans, simulating F uptake by plaque from saliva. To evaluate the effect of F on enamel, blocks were pretreated with NF or FD and the same protocol was used, but NF was used for brushing. After 30 min, plaque from some blocks was collected for determination of fluid F concentration, and a rinse with 20% sucrose solution was performed. After 45 min of this cariogenic challenge, demineralization was evaluated in enamel blocks by surface microhardness. Results: After brushing with NF or FD, significantly different (p<0.05) plaque fluid F concentrations (µM, Avg±SD) were found (2.0±0.4 and 508.0±436.5, respectively), and a lower enamel demineralization was observed for FD when compared to NF (p<0.05). F in plaque fluid on blocks pretreated with dentifrices NF and FD, when NF dentifrice was used for brushing was, respectively, 2.1±0.6 and 17.2±4.4, with significant differences between them (p<0.05). However, the enamel blocks pretreated with NF or FD did no not differ (p>0.05) in terms of resistance to demineralization. Conclusion: The results suggest that F in plaque may be more relevant to inhibit enamel demineralization than products formed on enamel by FD use.

Supported by FAPESP (05/04703-0 and 06/01193-3)