Association between red biofluorescence and microbial dysbiosis in cariogenic biofilms: an in vitro study.

Dental caries is driven by microbial dysbiosis rather than single pathogens. Red biofluorescence (RF), emitted from porphyrin-producing bacteria, has been proposed as a non-invasive indicator of dysbiosis. This study aimed to evaluate whether RF intensity reflects caries-related dysbiosis during in vitro biofilm maturation. Saliva-derived microcosm biofilms were grown on hydroxyapatite discs under cariogenic conditions for seven days. RF intensity was measured using Quantitative Light-induced Fluorescence-Digital (QLF-D) and fluorescent hyperspectral imaging (FHSI). Microbial composition was analyzed by 16S rRNA sequencing. A caries-related dysbiosis index was defined from eight cariogenic species consistently reported in clinical lesions. Correlations between RF intensity and dysbiosis index were assessed, and partial least squares regression (PLSR) identified taxa contributing to RF. RF intensity increased markedly with biofilm maturation (13.6-fold at day 7, p < 0.05). The dysbiosis index also rose 5.8-fold, showing a strong correlation with RF intensity (ρ = 1.00, p < 0.01). Anaerobic species such as Veillonella dispar and Granulicatella adiacens group contributed most strongly to RF expression (VIP > 1.0). RF intensity reflects both microbial compositional shifts and dysbiosis in cariogenic biofilms. RF may serve as a comprehensive, non-invasive biomarker of pathogenic biofilm activity and caries risk. This study demonstrated that RF can reflect changes in the composition of caries-related microorganisms and the level of caries-related dysbiosis during in vitro biofilm maturation.