Fluoride concentration and amount of dentifrice influence enamel demineralization in situ

Abstract

Objectives This study evaluated the effect of conventional (CD, 1100 ppm F) and low-fluoride (LFD, 550 ppm F) dentifrices, applied in different quantities, on enamel demineralization, and on fluoride (F) concentrations in the dental biofilm formed in situ. Methods Five combinations of dentifrices and quantities were tested: placebo (P–F-free) applied on all brush bristles; LFD applied by the transversal technique (0.3 g–T1) or on all bristles (0.6 g–T2); and CD applied in a pea-sized amount (0.15 g–T3) or by the transversal technique (0.3 g–T4), in order to produce comparable intensities (F concentration in the dentifrice × amount applied to the brush). Volunteers (n = 13, 20–36 years old) wore palatal devices containing 4 bovine enamel blocks, and performed cariogenic challenges (30% sucrose solution) 6×/day, and brushing 3×/day, following a double-blind, cross-over and randomized protocol. On the 8th day, biofilm was collected 5 and 60 min after brushing. The percentage of surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN) and biofilm F concentrations (solid and fluid phases) were determined. Data were analyzed by repeated-measures ANOVA, Student-Newman-Keuls test, and Pearson's correlation coefficient (p < 0.05). Results Significantly lower ΔKHN was observed for treatments with higher intensity (T2 and T4) in comparison with the lower intensity (T1 and T3). A strong correlation was observed between ΔKHN and F concentrations in total biofilm (r = −0.71) and biofilm fluid (r = −0.72) 5 min after brushing. Conclusions The treatment intensity has a significant influence on the development of caries lesions in situ. Clinical significance: The intensity of treatment (amount of dentifrice × concentration) during brushing seems to be a more relevant parameter of clinical efficacy than simply observing the F concentration of the product. The use of a small amount of CD significantly reduced the protective effects against enamel demineralization.