The Inhibitory Effects Of Streptococcus Oligofermentans On Root Caries

To investigate the impacts of Streptococcus oligofermentans, an oral commensal, on the cariogenicity of root surface plaque biofilms, and its inhibition on root caries in a rat model. Root surface plaques from root-caries patients and caries-free individuals were inoculated into a polystyrene peg model for 24 h, then cultured with or without S. oligofermentans under cariogenic pH-cycling conditions to form 72-h biofilms. Subsequently, the biofilms were subjected to biomass assay, lactate and H₂O₂ quantification, and qPCR analysis for S. oligofermentans colonization. In a root caries model, rats were received the following treatments respectively: no treatment, S. oligofermentans alone, cariogenic microbes (Streptococcus mutans, Actinomyces viscosus and Candida albicans), S. oligofermentans followed by cariogenic microbes, cariogenic microbes followed by low- or high-frequency treatment of S. oligofermentans. After 6 weeks, biosafety was assessed via organ histology, and root caries severity evaluated using Doff’s score and micro-CT. S. oligofermentans successfully colonized the pre-formed root-caries and caries-free plaque biofilms, significantly reducing biomass and acid production while increasing H₂O₂ generation (p<0.05). Pretreatment and treatment with low- or high-frequency S. oligofermentans significantly reduced root caries severity in rats (p<0.0001). Additionally, S. oligofermentans treatment alone displayed no toxicity to rat organs. S. oligofermentans effectively colonizes root surface plaque biofilms and suppresses their cariogenicity in vitro, as well as mitigates root caries severity in vivo, suggesting its inhibition on root caries.