UCSF

Periodontitis is a chronic, multifactorial inflammatory disease affecting 42% of US adults over the age of 30, characterized by progressive destruction of tooth-supporting structures associated with dysbiotic subgingival biofilms. Treponema denticola, a member of the Red complex, is one of the identified pathogenic bacteria that is strongly associated with the progression of periodontal disease. Advances in full-length 16S rRNA sequencing now allows for high-resolution taxonomic identification of Treponema species, including uncultivable phylotypes previously undetectable by traditional methods. The aim of this study was to investigate the relationship between subgingival Treponema community composition and clinical treatment outcomes following non-surgical periodontal therapy, with the hypothesis that greater reductions in Treponema relative abundance would be associated with improved clinical outcomes.Twenty-eight patients were initially enrolled in this study. Subjects over the age of 18 years-old with a diagnosis of Localized Stage 3 or 4, Grade B or C Periodontitis were eligible for this study. Subjects were excluded if they had taken any antibiotics, steroids, or immunosuppressive medications or received a professional dental cleaning within three months of the baseline examination. Six subjects did not return for non-surgical therapy, and three subjects did not return for the one-month follow-up evaluation appointment scheduled 4–6 weeks after scaling and root planning (SRP), leaving nineteen patients included in the final analysis (n = 19). Subgingival plaque samples were collected at baseline (T1) and at one-month follow-up (T3) from three teeth that presented with at least one site with CAL > 5mm and PPD > 6 mm. Full-length 16S rRNA sequencing was performed using the Oxford Nanopore platform and processed with the EMU pipeline to characterize the subgingival Treponema community. The primary outcome was the association between Treponema abundance the percentage of sites with clinical attachment loss > 5mm. The secondary outcomes were the association between Treponema abundance and the percentage of sites with probing depth > 6mm and percentage of sites with bleeding on probing. All statistical analyses were conducted in R (version 4.3.1) with significance set at α = 0.05.SRP produced significant improvements in all three clinical outcomes, with significant reductions in the percentage of sites with CAL ≥5 mm (55.6% to 33.3%, p = 0.0003), PPD ≥6 mm (27.8% to 16.7%, p = 0.0002), and bleeding on probing (BOP) (44.4% to 16.7%, p = 0.0027). Despite these clinical improvements, SRP did not produce a statistically significant shift in overall Treponema community composition (PERMANOVA, p = 0.061), total Treponema abundance (p = 0.072), alpha diversity, or individual species abundance after FDR correction, suggesting that non-surgical periodontal therapy alone may not be sufficient in diminishing the relative abundance of the Treponema community. Among the 13 variables tested, BOP was the only variable to remain significant after Benjamini-Hochberg FDR correction in the PERMANOVA (R² = 0.104, F = 4.16, p = 0.001, p-adj = 0.013). Total Treponema relative abundance at follow-up was strongly positively correlated with BOP at follow-up (ρ = 0.841, p < 0.001), and the change in Treponema abundance from baseline to follow-up was positively correlated with the change in BOP over the same period (ρ = 0.644, p = 0.003). Patients in the High BOP tertile at follow-up retained significantly greater Treponema abundance compared to those in the Low BOP tertile (χ² = 6.63, p = 0.036). Notably, two subjects had no detectable Treponema at either timepoint yet demonstrated clinically significant improvements in CAL, PD, and BOP, indicating that Treponema-independent pathways of periodontal disease and recovery exist.These findings suggest that Treponema abundance is more closely linked to active periodontal inflammation than to cumulative tissue destruction, and that resolution of inflammation following SRP may be the primary driver of Treponema reduction. Sociodemographic factors, particularly education level and race/ancestry, explained substantial variance in Treponema community composition, highlighting the potential role of social determinants of health in shaping the subgingival microbiome. Future studies with larger sample sizes and longer follow-up periods are needed to confirm and extend these observations.