Tracking metabolic changes in the oral environment after multi-bracket treatment via salivary metabolomics

Background Orthodontic appliances are known to alter the oral environment, yet their impact on salivary biochemistry remains poorly characterized. This study investigates the metabolic alterations in saliva during and after fixed orthodontic treatment using a non-targeted metabolomics approach.Methods Unstimulated whole saliva samples were collected from six patients at two time points: before debonding (T₀) and two weeks post-debonding (T₁). Metabolite extraction was performed, followed by high-throughput analysis using LC-MS/MS. Data processing and feature identification were conducted using XCMS and MS2Compound tools. Metabolites were annotated against HMDB and microbial databases. Statistical analysis was performed using MetaboAnalyst 4.0.Results A total of 2,153 metabolites were identified, with 739 unique to T₀ and 1,094 exclusive to T₁. Fifty shared metabolites exhibited significant fold-change. Post-treatment samples showed enriched pathways related to homocysteine degradation, taurine metabolism, CoA biosynthesis, and inositol phosphate metabolism. Microbial metabolites such as FMNH₂ and N-acetyl-muramoyl peptides indicated functional shifts in the oral microbiome. Enrichment of pathways like the Warburg effect and thiamine biosynthesis suggested microbial adaptation and ecological realignment post-appliance removal.Conclusion Fixed orthodontic appliances induce substantial metabolic changes in saliva, extending beyond mechanical effects to biochemical and microbial dynamics. Salivary metabolomics provides a powerful, non-invasive tool to monitor treatment-induced alterations and may support more personalized and biologically informed orthodontic care.