Comparative Analysis of Root Canal Microbiota in Diabetic and Systemically Healthy Patients

A total of 39 participants aged 18 to 65 years were enrolled in the study, including 21 patients with Diabetes Mellitus and 18 systemically healthy individuals (controls). In the diabetic group, 12 teeth were diagnosed with persistent endodontic infections (SEI) and 9 with primary endodontic infections (PEI). In the healthy group, 12 teeth presented with SEI and 6 with PEI. Root canal samples were obtained using sterile paper points, transferred into Eppendorf tubes containing phosphate-buffered saline (PBS), and stored at -80 °C until analysis. The V3-V4 hypervariable regions of 16S rRNA from both sample types were amplified and sequenced using the Illumina MiSeq platform. Amplicon sequence variants (ASVs), generated via the DADA2 pipeline, were analyzed in the QIIME2 environment and taxonomically assigned using the SILVA database. Microbial richness and diversity were assessed using alpha diversity indices (Chao1, Shannon, Simpson, Faith's PD, Fisher alpha) and beta diversity metrics (Bray-Curtis, Jaccard, Unweighted UniFrac, and Weighted UniFrac). Alpha and beta diversity metrics were compared using the Kruskal-Wallis test and pairwise permutational multivariate analysis of variance (PERMANOVA), respectively, via the phyloseq package in R (version 4.1). Differentially abundant taxa were identified using Linear Discriminant Analysis Effect Size (LEfSe).