Comparison of Long-Term Oral Bacterial Flora Before and After Orthognathic Surgery in Surgical Orthodontic Treatment

<b>Background/Objectives:</b> Multi-bracket appliances are essential in surgical orthodontic treatment, and perioperative oral management during orthognathic surgery is critical. Thorough plaque control, appropriate use of antibiotics, and shortening of operative time have been reported to be effective in preventing postoperative infections and ensuring surgical success. As highly invasive orthognathic surgery involving osteotomy may influence the postoperative oral microbiota, this study aimed to investigate the characteristics of and clarify the changes occurring in the salivary oral microbiota after orthognathic surgery. <b>Methods:</b> The study included 14 patients (Group S; mean age 29.3 ± 9.8 years) who underwent surgical orthodontic treatment and 15 control patients (Group C; mean age 27.1 ± 8.7 years) who received orthodontic treatment alone. Salivary samples were analyzed via 16S rRNA gene sequencing, and the relative abundances of bacteria were evaluated using the Linear Discriminant Analysis Effect Size. <b>Results:</b> The prevalence of <i>Neisseria</i>, which is associated with early biofilm formation, decreased over time in both groups. In contrast, <i>Streptococcus</i> exhibited an increase in prevalence. In Group S, members of <i>Pseudomonas</i>, the family Saccharimonadaceae, and the order Rhizobiales showed increases at 5-8 months post-surgery. <b>Conclusions:</b> Surgical orthodontic treatment may influence the oral microbiota and promote colonization by opportunistic pathogens. Instructions regarding oral hygiene and appropriately timed professional cleaning interventions are critical in preventing such colonization. Longitudinal monitoring of the microbiota using metagenomic analysis may be useful for future perioperative management and guidance of oral hygiene.