Objective: To investigate the impact of appliance removal on oral microbial diversity, composition, and abundance using metagenomic sequencing. It aims to identify the core microbiome and assess changes between mid-treatment and 2 weeks after debonding to better understand the relationship between orthodontic therapy and oral health. Methods: This longitudinal cohort study recruited 26 patients undergoing fixed orthodontic treatment between January 2022 and June 2023. Saliva samples were collected at two predefined time points: mid-treatment (T0, defined as before appliance removal) and 2 weeks after debonding (T1). Microbial DNA was extracted and the V1–V3 hypervariable regions of the 16S rRNA gene were sequenced using Illumina NovaSeq. Bioinformatics analysis was performed using QIIME and the SILVA database to evaluate microbial diversity and composition at T0 and T1. Beta diversity metrics and statistical tests, including PERMANOVA and Wilcoxon signed-rank tests, were applied to identify significant differences ( P < 0.05). Effect sizes with 95% confidence intervals (CIs) were reported. Results: The analysis revealed significant shifts in microbial diversity and composition between T0 and T1. A total of 189 species across 63 genera were identified, with Firmicutes, Bacteroidetes , Proteobacteria, Actinobacteria, and Fusobacteria as dominant phyla. Genera such as Fusobacterium periodonticum (↑ 12.4%, 95% CI = 10.1–14.7) and Veillonella parvula (↑ 9.8%, 95% CI = 7.6–11.3) increased after debonding, while Prevotella melaninogenica (↓ 10.2%, 95% CI = 8.1–12.0) and Rothia dentocariosa (↓ 7.9%, 95% CI = 6.3–9.2) decreased. Beta diversity analysis confirmed a statistically significant microbial community shift ( P < 0.05). Conclusion: This study demonstrated significant microbial shifts between mid-treatment and 2 weeks after debonding, including increases in potentially pathogenic genera and alterations in the core microbiome. These findings indicate microbial changes persist for at least 2 weeks after appliance removal. Further research with pre-treatment baselines and extended follow-up is required to better define the long-term trajectory of these changes.
Fathima et al. (Thu,) studied this question.