Study on pathogenic mechanisms of metabolic pathways and key metabolites associated with black stain with or without severe early childhood caries.

OBJECTIVE: To investigate dental plaque metabolic profile differences between preschoolers with Black Stain and Caries-free (BSCF) versus Severe Early Childhood Caries with Black Stain (SECCBS) to elucidate S-ECC pathogenesis. DESIGN: Dental plaque was collected from 59 preschoolers aged 3-6 (BSCF, n = 29; SECCBS, n = 30) and analyzed using ultra-high performance liquid chromatography-tandem mass spectrometry. Differential metabolites (DMs) were identified via partial least squares discriminant analysis. KEGG pathway analysis and Metorigin provided functional and source-tracking insights. Weighted Gene Co-expression Network Analysis (WGCNA) identified hub metabolites linked to clinical traits, while 10 machine learning models were developed for diagnostic prediction. RESULTS: Profiling identified 1069 metabolites, predominantly lipids/lipid-like molecules (24.60%) and organic acids/derivatives (11.51%). Eighty-five DMs were identified between groups; four were significantly downregulated ( Δ17-6-keto prostaglandin F1α, VLH, DPK, and N'-[1-(2-hydroxyphenyl)ethylidene]-3-methoxybenzohydrazide). L-glutamate was significantly upregulated in SECCBS, whereas L-(+)-citrulline was downregulated. KEGG analysis mapped DMs primarily to nucleotide, carbohydrate, amino acid, and lipid metabolism. Metorigin revealed 78.6% of metabolites were co-derived from diet, microbiota, and pharmaceuticals. WGCNA identified 31 modules, two positively correlating with SECCBS. The top-performing machine learning model achieved robust AUC performance for clinical stratification. CONCLUSIONS: Distinct plaque metabolomic profiles differentiate SECCBS from BSCF. Alterations in nucleotide metabolism, the pentose phosphate pathway, and specific amino acid pathways drive SECC progression. Furthermore, 2'-deoxyuridine and 6-phosphogluconic acid emerge as potential biomarkers for early SECC diagnosis, prevention, and targeted clinical intervention.