Association of PCR-based oral bacterial profiles with fluorescence-detected plaque and caries experience in 3-year-old children: a cross-sectional study

Quantitative light-induced fluorescence (QLF) is widely used to detect dental plaque. However, the microbial composition of QLF-detected plaque in young children remains poorly characterized. This cross-sectional study aimed to assess the associations among 10 oral disease-associated bacterial species, QLF-detected plaques, and caries in 3-year-old children. Ninety-nine 3-year-old children participated in this study. Real-time polymerase chain reaction (PCR) quantified 10 target species, which were analyzed individually and as functional groups (red-complex, orange-complex, and caries-associated groups). Plaque on the labial surfaces was measured by QLF imaging and scored using the Fluorescence Patient Hygiene Performance Index (F-PHPI). The caries experience (dft) was clinically recorded. Associations were evaluated using Spearman’s correlation and regression analyses. The F-PHPI score was significantly associated with Fusobacterium nucleatum (F. nucleatum) (ρ = 0.455, p < 0.05), the orange complex (ρ = 0.456, p < 0.001), and total bacterial load (ρ = 0.479, p < 0.001). Regression analysis showed that orange-complex levels predicted F-PHPI scores (R2 = 0.17). dft correlated with the caries-associated group (ρ = 0.282, p < 0.05), and logistic regression identified this group as a significant predictor (OR = 1.34, p = 0.01), with Streptococcus mutans (S. mutans) the only individual species associated with caries (ρ = 0.286, p < 0.05). In 3-year-old children, QLF-detected plaque was significantly associated with orange-complex bacteria. The F-PHPI served as a potential indicator of microbial load, with regression models confirming its predictive relationship with pathogenic bacterial groups. These findings support QLF imaging as a noninvasive tool for early microbial risk assessment in pediatric populations.