Influence of a novel pH-cycling model using dental microcosm biofilm on the remineralizing efficacy of fluoride in early carious lesions

Abstract

Objectives: To evaluate the remineralizing efficacy of fluoride in early carious lesions using a novel microbial pH-cycling model that combines the chemical pH-cycling model with dental microcosm biofilms. Materials and methods: Artificial carious lesions were formed in 48 bovine incisors. The chemical and microbial pH-cycling models were applied to 24 specimens, respectively; the latter was applied after formation of dental microcosm biofilms for 6 days, based on the human saliva inoculation. The pH-cycling schedule was repeated for 12 days. All specimens were evaluated for fluorescence loss (ΔF) using quantitative light-induced fluorescence-digital before and after the pH-cycling. Specimen biofilms were further analyzed for red/green values (R/G ratios) and colony-forming units (CFUs). One-way analysis of variance and Tukey’s post hoc analysis were used to analyze change in fluorescence loss (ΔΔF) according to the pH-cycling model and treatment. Results: When the chemical pH-cycling and microbial pH-cycling models were used, ΔΔF was 1.36 (p = 0.008) and 1.17 (p > 0.05) times higher, respectively, in the fluoride-treated group than that in the distilled water-treated group. In the microbial pH-cycling model, R/G ratios and CFU counts of biofilms were not significantly different between treatments (p > 0.05). Conclusions: No significant difference was observed in the remineralizing efficacy of fluoride according to the presence of dental biofilms covering early carious lesions. Clinical relevance: The remineralizing efficacy of fluoride could be overestimated in the absence of dental biofilms. Therefore, for accurate evaluation of the clinical value of remineralizing agents, dental biofilms should be included in in vitro tests. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.