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Potential relationship between clinical symptoms and the root canal microbiomes of root filled teeth based on the next-generation sequencing.

AIM
To detemine the microorganism in root canal systems of root filled teeth with periapical disease and their relationship with clinical symptoms using next-generation sequencing (NGS).


METHODOLOGY
The roots of 10 extracted teeth were collected from ten patients who presented with post-treatment apical periodontitis (6 with symptoms and 4 without symptoms). Each root was divided horizontally into two parts (apical and coronal segments) and cryo-pulverized. Microbial communities were detected using 16S rDNA hypervariable V3-V4 region. The diversity, principal coordinate analysis (PCoA) and linear discriminant analysis effect size (LEfSe) were performed in the symptomatic and asymptomatic groups (apical and coronal parts, respectively). A Mann-Whitney test and an analysis of similarities were applied for intergroup analysis, at a significance level of 5%.


RESULTS
A total of 23 phyla, 257 genera, and 425 species were detected. Firmicutes was the most abundant phylum in all samples. Three phyla (Fusobacteria, Synergistetes and unidentified_Bacteria) and seven genera (Fusobacterium, Porphyromonas, Phocaeicola, Olsenella, Campylobacter, Tannerella and Fretibacterium) were significantly more abundant in the symptomatic patients (P < 0.05), whereas asymptomatic patients had more Sphingomonas. The species more significantly abundant in the symptomatic samples were Porphyromonas gingivalis, Phocaeicola abscessus, Campylobacter showae, Tannerella forsythia and Olsenella uli (P < 0.05).


CONCLUSIONS
A higher microbial diversity was observed in root filled teeth with post-treatment apical periodontitis compared to earlier reports. Several genera and species in root canal systems might be associated with clinical symptoms of post-treatment apical periodontitis.