Anti-Caries Efficacy of Fluoride at Increasing Maturation of a Microcosm Biofilm

Abstract

Dental biofilm is a main contributing factor in the initiation and progression of dental caries. The maturation of dental biofilms is expected to alter the anti-caries efficacy of fluoride compounds. In the first aim, we conducted a series of modeldevelopment experiments to test different variables to standardize a reproducible in-vitro microbial caries model. We evaluated: surface conditioning using saliva; sucrose concentrations and caries lesion severity; growth media conditions and mineral saturation; dental substrate types; pH cycling protocol characteristics. In the second aim, we used the developed model to evaluate the changes in the anti-caries efficacy of three fluoride compounds (Sodium fluoride (NaF); Stannous fluoride (SnF2); Amine fluoride (AmF); and deionized water (DIW- negative control)) at increasing maturation of a microcosm biofilm. We continued the pH cycling protocol for 4 days, 8 days, and 12 days. We tested biofilm cariogenicity and carious lesion severity at each maturation stage. In the third aim, we used the developed model to test the effect of different exposure periods (early vs. late exposure) of the biofilm to three fluoride compounds (NaF, SnF2, AmF, DIW) in comparison to DIW. We also evaluated the recovery of biofilm cariogenicity with each exposure period. We evaluated, for each exposure period and recovery stage, biofilm cariogenicity and carious lesion severity. We analyzed the relationships between different variables (biofilm age, fluoride compound type, exposure period) using ANOVA models. In conclusion: 1. The present model allows testing the effect of biofilm maturation on the anti-caries efficacy of fluoride compounds. 2. Biofilm maturation plays an important role in increasing biofilm tolerance against fluoride treatment; it could also influence the selection of fluoride compounds to achieve optimum cariostatic effect. 3. Exposure period, and type of fluoride compound, both influence the biofilm tolerance to fluoride anti-caries effect; they may also result in a sustainable release of fluoride over time.