The objectives of this study were to investigate the effects of a novel method using flavonoids to inhibit Streptococcus mutans (S. mutans), Candida albicans (C. albicans) and dual-species biofilms and to protect enamel hardness in a biofilm-based caries model for the first time. Several flavonoids, including baicalein, naringenin and catechin, were tested. Gold-standard chlorhexidine (CHX) and untreated (UC) groups served as controls. Optimal concentrations were determined by cytotoxicity assay. Biofilm MTT, colony-forming-units (CFUs), biofilm biomass, lactic acid and polysaccharide production were evaluated. Real-time-polymerase-chain reaction (qRT-PCR) was used to determine gene expressions in biofilms. Demineralization of human enamel was induced via S. mutans-C. albicans biofilms, and enamel hardness was measured. Compared to CHX and UC groups, the baicalein group achieved the greatest reduction in S. mutans, C. albicans and S. mutans-C. albicans biofilms, yielding the least metabolic activity, polysaccharide synthesis and lactic acid production (p < 0.05). The biofilm CFU was decreased in baicalein group by 5 logs, 4 logs, 5 logs, for S. mutans, C. albicans and S. mutans-C. albicans biofilms, respectively, compared to UC group. When tested in a S. mutans-C. albicans in vitro caries model, the baicalein group substantially reduced enamel demineralization under biofilms, yielding an enamel hardness that was 2.75 times greater than that of UC group. Hence, the novel baicalein method is promising to inhibit dental caries by reducing biofilm formation and protecting enamel hardness.

中文翻译：

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类黄酮黄芩素抑制口腔生物膜并保护牙釉质硬度以对抗龋齿

本研究的目的是研究一种使用类黄酮抑制变形链球菌( S. mutans )、白色念珠菌( C. albicans)的新方法的效果) 和双物种生物膜，并首次在基于生物膜的龋齿模型中保护牙釉质硬度。测试了几种类黄酮，包括黄芩素、柚皮素和儿茶素。金标准洗必泰 (CHX) 和未处理 (UC) 组作为对照。通过细胞毒性测定确定最佳浓度。评估了生物膜 MTT、菌落形成单位 (CFU)、生物膜生物量、乳酸和多糖产量。实时聚合酶链反应 (qRT-PCR) 用于确定生物膜中的基因表达。通过变形链球菌-白色念珠菌生物膜诱导人牙釉质脱矿，并测量牙釉质硬度。与 CHX 和 UC 组相比，黄芩素组的变形链球菌减少最多，C. albicans和S. mutans - C. albicans生物膜，产生最少的代谢活性、多糖合成和乳酸产生 ( p < 0.05)。与 UC 组相比，对于变形链球菌、白色念珠菌和变形链球菌-白色念珠菌生物膜，黄芩素组的生物膜 CFU 分别降低了 5 个对数、4 个对数、5 个对数。在S. mutans - C. albicans中进行测试时在体外龋齿模型中，黄芩素组显着减少了生物膜下的牙釉质脱矿，牙釉质硬度是 UC 组的 2.75 倍。因此，新的黄芩素方法有望通过减少生物膜形成和保护牙釉质硬度来抑制龋齿。