Erythritol attenuates cariogenic traits in single-species models and alters bacterial composition in a dual-species biofilm.

OBJECTIVE: To evaluate the effects of erythritol on functional cariogenic traits in separate single-species Streptococcus mutans and Lacticaseibacillus acidophilus models and to characterize relative species composition in a simplified dual-species biofilm. DESIGN: Functional microbial, biochemical, structural, molecular, and hard-tissue outcomes were evaluated in separate single-species models. Species-specific qPCR was used to quantify the relative abundance of S. mutans and L. acidophilus in a simplified dual-species biofilm. RESULTS: Erythritol reduced bacterial growth and viable colony formation in both species. Medium acidification was attenuated, with slower pH decline and lower lactic acid accumulation in erythritol-treated groups. Biofilm biomass and metabolic activity were lower at both 24 h and 48 h. In the dual-species biofilm, the relative abundance of S. mutans decreased, whereas that of L. acidophilus increased correspondingly. Microscopy showed reduced viable bacterial distribution, weaker dentin-surface adhesion, less compact biofilm architecture, and diminished extracellular matrix deposition. Separate single-species hard-tissue analyses demonstrated lower Ca2 + release, higher endpoint surface microhardness, lower surface hardness loss, and higher cross-sectional microhardness profiles. RT-qPCR showed reduced expression of selected virulence-related genes, particularly in S. mutans. Across most assays, the effects observed at 6% and 8% erythritol were similar. CONCLUSIONS: Erythritol attenuated multiple cariogenic traits in separate single-species S. mutans and L. acidophilus assays and altered relative species composition in a dual-species biofilm. The composition data do not establish reduced dual-species functional virulence or clinical carioprotection.