Indiana University-Purdue University Indianapolis (IUPUI) / 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. / 2021-08-21

Both Candida albicans and lactobacilli are common colonizers of carious lesions in children and adolescents. The purpose of this study is to compare the velocity of acid production between C. albicans and several Lactobacillus species at different pH levels and concentrations of glucose. Washed, pure resting-cell suspensions were obtained by culturing a total of 28 oral isolates comprising the species C. albicans, Lactobacillus rhamnosus, Lactobacillus paracasei paracasei, Lactobacillus paracasei tolerans and Lactobacillus delbrueckii lactis. Acid production from glucose was determined at a constant pH of 7.0, 5.5, 5.0 and 4.0 by repeated titrations with NaOH in an automated pH-stat system. Acid formation rates of yeast and lactobacilli proved to be similar at both neutral and low pH, while in a moderately acidic environment C. albicans produced less acid than the lactobacilli. Ion chromatographic analysis of the cell-free medium after titration revealed pyruvate to be the predominant organic acid anion secreted by C. albicans. The proportion of organic acids to overall acid production by the yeast was below 10% at neutral conditions, in contrast to 42–66% at pH 4.0. Compared to lactobacilli, yeast required a concentration of glucose that was about 50 times higher to allow acid production at half the maximum speed. Considering the clinical data in the literature about the frequency and proportions of microorganisms present in early childhood caries lesions, the contribution of oral lactobacilli as well as C. albicans to overall microbial acid formation appears to be important. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Both Candida albicans and lactobacilli are common colonizers of carious lesions in children and adolescents. The purpose of this study is to compare the velocity of acid production between C. albicans and several Lactobacillus species at different pH levels and concentrations of glucose. Washed, pure resting-cell suspensions were obtained by culturing a total of 28 oral isolates comprising the species C. albicans, Lactobacillus rhamnosus, Lactobacillus paracasei paracasei, Lactobacillus paracasei tolerans and Lactobacillus delbrueckii lactis. Acid production from glucose was determined at a constant pH of 7.0, 5.5, 5.0 and 4.0 by repeated titrations with NaOH in an automated pH-stat system. Acid formation rates of yeast and lactobacilli proved to be similar at both neutral and low pH, while in a moderately acidic environment C. albicans produced less acid than the lactobacilli. Ion chromatographic analysis of the cell-free medium after titration revealed pyruvate to be the predominant organic acid anion secreted by C. albicans. The proportion of organic acids to overall acid production by the yeast was below 10% at neutral conditions, in contrast to 42–66% at pH 4.0. Compared to lactobacilli, yeast required a concentration of glucose that was about 50 times higher to allow acid production at half the maximum speed. Considering the clinical data in the literature about the frequency and proportions of microorganisms present in early childhood caries lesions, the contribution of oral lactobacilli as well as C. albicans to overall microbial acid formation appears to be important. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.