Interplay between genetically predicted gut microbiota and chronic apical periodontitis: a Mendelian randomization analysis

Background Whether alterations in the gut microbiota play a causal role in chronic apical periodontitis (CAP) remains uncertain. A two-sample Mendelian randomization (MR) analysis was used in this study to assess the potential causal effect of gut microbiota on CAP risk.Methods Gut microbiota summary statistics were from the MiBioGen consortium’s largest GWAS, and CAP data from the FinnGen project. The inverse variance–weighted method was the main analytic approach, and sensitivity analyses verified instrument robustness.Results Two microbial taxa showed positive causal effect with CAP: Lachnospiraceae FCS020 group (odds ratio [OR] = 1.244, 95% confidence interval [CI]: 1.059–1.461, p = 0.008) and Ruminococcus2 (OR = 1.196, 95% CI: 1.039–1.377, p = 0.013). Conversely, Escherichia-Shigella exhibited an inverse genetic association with CAP risk (OR = 0.746, 95% CI: 0.620–0.897, p = 0.002). Sensitivity analyses supported the stability of these findings and confirmed that the effect estimates were directionally consistent, thereby strengthening confidence in the primary results.Conclusions This MR analysis provides evidence of a genetic relationship between gut microbiota composition and susceptibility to CAP. The findings broaden our understanding of microbial changes in CAP-affected tissues, and suggest a genetic association between alterations in the composition of the gut microbiota and CAP risk.