Validation of a Cariogenic Biofilm Model to Evaluate the Effect of Fluoride on Enamel and Root Dentine Demineralization

Abstract

Due to gingival recession both enamel and root dentine are at risk of developing caries. Both tissues are exposed to a similar environment, however there is not a validated model to evaluate the effect of fluoride on these dental substrates simultaneously. Hence, this study aimed to validate a caries model to evaluate the effect of fluoride to prevent demineralization on enamel and root-dentine. Streptococcus mutans UA159 biofilms were formed on saliva-coated bovine enamel and root dentine slabs (n = 12 per group) mounted in the same well of culture plates. The biofilms were exposed 8×/day to 10% sucrose and treated 2×/day with fluoridated solutions containing 0, 150, 450, or 1,350 ppm F; thus, simulating the use of low to high fluoride concentration toothpastes. The pH values of the culture medium was monitored 2×/day as a biofilm acidogenicity indicator. After 96 h, biofilms were collected for fluoride concentration analysis. The percentage of surface hardness loss (%SHL) was calculated for slabs. The fluoride uptake by the enamel and dentine was also determined. The model showed a dose-response because the biofilm and fluoride uptake increased and %SHL decreased at increasing fluoride concentrations (p < 0.05). Fluoride in the biofilm formed on dentine and fluoride uptake by dentine were higher than those for enamel. With the same fluoride concentration treatment, the percentage of reduction of demineralization was lower for dentine than for enamel. In conclusion, the model was validated in terms of a dose-response effect of fluoride on enamel and root dentine. Furthermore, the findings support the clinical data, suggesting that higher fluoride concentrations are necessary to control caries of root dentine than of enamel.

Effect of Fluoride Concentration on Reduction of Enamel Demineralization According to the Cariogenic Challenge

“…The results of %SHL and ∆S are also confirmed by fluoride concentration in enamel (Table 2), which is an indicator of fluoride effect in de-and remineralization (28). Decreased mineral loss observed either for %SHL or ∆S in groups treated with fluoridated solutions, especially those exposed to high cariogenic challenge, are supported by the highest fluoride incorporation in enamel found in these groups.…”

Influence of biofilm formation on the mechanical properties of enamel after treatment with CPP-ACP crème

“…1,11,12 Thus, biofilm models have been used to evaluate the in vitro effect of toothpastes containing antimicrobial compounds such as fluoride on Streptococcus mutans biofilm formation.…”

Caries Progression: How Can We Control this Disease?

“…Although a fluoride dose-response concentration makes regular effect on enamel and dentine demineralization reduction, a study by Fernández et al [22] shows that the effect of fluoride is different on these dental substrates. While 450 ppm F produced a 60% demineralization reduction in enamel, in dentin this effect in the same percentage can only be obtained with 1350 ppm F.…”

“…This fact can be explained by the fact that dentin suffers twice as much demineralization as enamel, being considered more susceptible to caries [22][23][24].…”