Impact of Fixed Orthodontic Appliances on Oral Microbiome Diversity: A Longitudinal Study

Background: Fixed orthodontic appliances can modify the oral environment, potentially influencing microbial diversity and oral health. This study sought to assess alterations in oral microbiome diversity over the course of one year and find related factors. Study Design: Cross-sectional study Place and Duration of the Study: Orthodontics Department of Rehman College of Dentistry, Peshawar, Pakistan, from January to June 2024. Materials and Methods: A 12-month longitudinal study was conducted on 215 orthodontic patients. Oral samples were collected at baseline, 3, 6, and 12 months and analysed by 16S rRNA sequencing (Illumina MiSeq). The Shannon diversity index was used to quantify microbial diversity. Linear mixed models examined predictors of diversity change. Results: Microbial diversity declined from 3.45 ± 0.55 to 2.95 ± 0.58 (β = –0.18, 95% CI: –0.30 to –0.06, p = 0.004). Reduced brushing frequency, high sugar intake, and prolonged appliance duration were significantly associated with lower diversity. Conclusion: The variety of the oral microbiome diminishes progressively throughout fixed orthodontic treatment, with oral hygiene practices, dietary sugar consumption, and appliance duration serving as significant influencing variables. Highlighting efficient brushing and food regulation may assist in alleviating microbiota changes in orthodontic patients.