Salivary microbiome, metabolome and host immune changes in patients undergoing fixed orthodontic therapy
Creators: name: Daily, Madeleine L.
Publisher: name: University of Iowa
Year: 2026

description: BACKGROUND
description: Patients undergo fixed orthodontic treatment (FOT) to improve dental and facial aesthetics, correct occlusal function, and/or eliminate traumatic occlusion. However, many patients, especially teenagers, struggle to maintain good oral hygiene. This can result in plaque-related complications such as periodontal diseases, caries, and white spot lesions. Plaque-mediated diseases result from imbalances in the microbiome leading to an enrichment of disease associated pathogens in the microbial community and trigger host immune responses that can be destructive to tissues. Saliva samples can provide information about microbes, immune signatures, and metabolites present in the oral environment and are easy to collect during routine visits. We aimed to comprehensively characterize how the microbial composition, proinflammatory mediators, and metabolites of the salivary environment change throughout FOT.
description: METHODS
description: This cross-sectional study analyzed saliva samples from 55 orthodontic patients, aged 11-20 years, and 29 periodontally healthy control subjects not undergoing orthodontic treatment, matched for age, gender, and dentition. Unstimulated saliva samples were collected from patients at 6 months, 12 months, or 24 months into orthodontic treatment. DNA was isolated from saliva samples, quantified, and normalized. The V3-V4 regions of the 16S rRNA gene were amplified and sequencing was completed using the Illumina MiSeq platform to collect 300 base pair paired-end reads. Sequences were annotated against the SILVA database. Saliva samples were sent to the Metabolomics Core (FOEDRC) for metabolite extraction and derivatization and Gas Chromatography/Mass Spectrometry analysis. A MILLIPLEX® Multiplex for Luminex® Immunoassay (Millipore, Sigma Aldrich) was used to determine levels of multiple cytokines and immune mediators, including L-1β, IL-6, IL-8/CXCL8, IL-10, TNF-α, VEGF-A, TGF-β1, MIF, RANKL, M-CSF, and INF- γ, present in the saliva samples.
description: RESULTS
description: FOT was associated with a significant reduction in bacterial diversity compared to controls; however, the diversity was similar among different time points. With FOT, we saw an increase in many disease-associated species and a decrease in several health-associated and commensal species. Timepoint-specific shifts were observed in the salivary metabolome; metabolic biomarkers of caries and periodontal disease were most abundant at our earliest sample timepoints, 6 and 12 months. Salivary immune-biomarkers of caries and periodontitis, including TNF-α, IL-1β, IL-6, and IL-10 were elevated at later treatment timepoints.
description: CONCLUSION
description: Our cross-sectional study is a step towards comprehensively understanding how the salivary microbiome, metabolome, and host immune response change throughout FOT. The placement of fixed appliances induces dysbiosis in the salivary oral microbiome, which causes a shift in the salivary environment from health towards disease. Early disease intervention may be crucial for preventing negative sequalae of orthodontic treatment with fixed appliances. In the future, this foundation may aid in patient risk profiling and disease intervention during orthodontic treatment.