Streptococcus mutans is not the only species associated with caries lesions. Other potentially acidogenic and aciduric bacterial species, such as bifidobacteria, have been detected in various oral sites, including the initial carious lesions or cavities. Many of these bifidobacteria, called probiotics, are used in the food industry and consequently are widely consumed by children. The objectives of this study will be compare the ability to produce and tolerate acids, to form biofilm and to induce in vitro initial carious lesions by species of bifidobacteria compared to bacterial species already recognized in the context of dental caries. The following bacterial species will be included in this study: Bifidobacterium lactis, Bifidobacterium longum , Bifidobacterium animalis, Bifidobacterium dentium, Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus, Lactobacillus casei and Actinomyces israelli. In order to evaluate the cariogenic potential of these bacterial species, acidogenicity tests will be carried out by checking the final pH of the cultures after exposure to high glucose concentration, aciduric tests will be conducted to measure bacterial growth after exposure to acidic pH and in vitro biofilm formation will quantify biofilm biomass in an ELISA reader. Finally, tests for induction of initial caries lesions in bovine teeth will be conducted to check the thickness of the demineralized enamel using polarized light microscopy. Tests of biofilm and caries lesion induction will be performed with all strains combined or not with Streptococcus mutans. The data will be statistically analyzed, considering pd0,05.
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