Comparative analysis of the dental plaque metabolome in tooth stain and caries within primary dentition

BACKGROUND: Dental black tooth stain (BTS) has been epidemiologically associated with a lower prevalence of dental caries, yet the underlying metabolic mechanisms remain poorly understood. This study aimed to characterize the metabolic profiles of dental plaque to explore the association between tooth stain and low caries risk. METHODS: Dental plaque samples were collected from three groups of children: caries-free with BTS (CF-BTS), caries-free without BTS (CF), and severe early childhood caries without BTS (SECC). Metabolomic profiling was performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Multivariate statistical analyses, including PCA and OPLS-DA, were employed to identify differential metabolites (DMs). Metabolic pathway enrichment and metabolite source tracing were conducted using KEGG and MetOrigin databases. RESULTS: PCA showed excellent analytical stability, and OPLS-DA revealed distinct metabolomic profiles among groups. A total of 1,069 molecular features were detected, with 658 metabolites identified. Lipids and lipid-like molecules (39.97%) constituted the most abundant class. Venn analysis identified core differential metabolites, including irganox 259 (up-regulated in CF-BTS), Δ17-6-keto-PGF1α (up-regulated in CF-BTS), and 6-phosphogluconic acid (down-regulated in CF-BTS). MetOrigin analysis classified metabolites into host (n = 19), microbial (n = 98), and co-metabolic (n = 173) sources. KEGG enrichment indicated significant alterations in ABC transporters, pyrimidine metabolism, and neuroactive ligand-receptor interactions in BTS-associated plaque. CONCLUSION: Dental plaque associated with BTS exhibits a distinct metabolomic signature characterized by enhanced antioxidant capacity. These findings provide critical functional insights into the caries-protective mechanism of BTS and identify promising metabolic targets for the development of novel anti-caries strategies.