Longitudinal Characterization of Gingival Microbiota Following Periodontally Accelerated Osteogenic Orthodontics Surgery in Skeletal Class III Orthognathic Patients

Objective: Periodontally accelerated osteogenic orthodontics (PAOO) combines selective alveolar decortication with orthodontic force to accelerate tooth movement, but its influence on the gingival crevicular fluid (GCF) microbiome and early periodontal condition remains unclear. Methods: In this repeated-measures, within-subject longitudinal study, 18 GCF samples were collected from 6 skeletal class III orthognathic patients at baseline (A0), 2 weeks after PAOO (A2), and 4 weeks post-PAOO coinciding with 2 weeks of active orthodontic force application (A4). Microbiota were profiled by 2bRAD-M sequencing, and periodontal indices (plaque index, bleeding index, probing depth, keratinized gingiva width) were recorded. Results: Periodontal indices remained stable with no significant increase in plaque, bleeding, or probing depth; notably, keratinized gingiva width increased significantly at A2 and A4. α-diversity showed stable richness but reduced evenness at A4. β-diversity demonstrated progressive shifts, with A2 as a transitional stage. Multi-level taxonomic analysis was performed to characterize temporal changes in microbial community structure during treatment progression. At the phylum level, Proteobacteria remained dominant throughout the study, followed by Firmicutes, Actinobacteriota, and Bacteroidota. Genus-level analysis revealed core genera including Neisseria, Streptococcus, and Prevotella, while species-level comparison showed that Haemophilus parainfluenzae and Actinomyces oris were present across timepoints with varying abundance. LEfSe analysis identified stage-specific microbial markers across A0/A2/A4. Functional prediction suggested potential involvement in lysine biosynthesis, necroptosis, β-lactam resistance, and immune signalling pathways. Conclusions: In this pilot repeated-measures cohort, PAOO combined with early orthodontic force was associated with distinct temporal changes in the GCF microbiome while maintaining overall periodontal stability and increasing keratinized gingiva width. Predicted functional shifts may be relevant to host responses during early healing; however, mechanistic inferences require confirmation in larger longitudinal studies.