Abstract
IntroductionBacteria present in the apical root canal system are directly involved with the pathogenesis of post-treatment apical periodontitis. This study used a next-generation sequencing approach to identify the bacterial taxa occurring in cryopulverized apical root samples from root canal-treated teeth with post-treatment disease.MethodsApical root specimens obtained during periradicular surgery of ten adequately treated teeth with persistent apical periodontitis were cryogenically ground. DNA was extracted from the powder and the microbiome was characterized on the basis of the V4 hypervariable region of the 16S rRNA gene by using paired-end sequencing on Illumina MiSeq device.ResultsAll samples were positive for the presence of bacterial DNA. Bacterial taxa were mapped to 11 phyla and 103 genera composed by 538 distinct operational taxonomic units (OTUs) at 3% of dissimilarity. Over 85% of the sequences belonged to 4 phyla: Proteobacteria, Firmicutes, Fusobacteria and Actinobacteria. In general, these 4 phyla accounted for approximately 80% of the distinct OTUs found in the apical root samples. Proteobacteria was the most abundant phylum in 6/10 samples. Fourteen genera had representatives identified in all cases. Overall, the genera Fusobacterium and Pseudomonas were the most dominant. Enterococcus was found in 4 cases, always in relatively low abundance.ConclusionsThis study showed a highly complex bacterial community in the apical root canal system of adequately treated teeth with persistent apical periodontitis. This suggests that this disease is characterized by multispecies bacterial communities and has a heterogeneous etiology, because the community composition largely varied from case to case.
Highlights
Bacteria present in the apical root canal system are directly involved with the pathogenesis of post-treatment apical periodontitis
Bacterial taxa were mapped to 11 phyla and 103 genera composed by 538 distinct operational taxonomic units (OTUs) at 3% of dissimilarity
Over 85% of the sequences belonged to 4 phyla: Proteobacteria, Firmicutes, Fusobacteria and Actinobacteria
Summary
Apical root specimens obtained during periradicular surgery of ten adequately treated teeth with persistent apical periodontitis were cryogenically ground. Each patient contributed one root canal-treated tooth, which was asymptomatic and presented with an apical periodontitis lesion as determined radiographically and confirmed by CBCT (requested for surgery planning). Other inclusion criteria were: previous root canal treatment or retreatment performed at least more than 1 year before; the lesion remained the same size or increased as compared with radiographs taken immediately after the initial treatment/retreatment; teeth with satisfactory coronal restorations and no direct exposure of the root canal filling material to the oral cavity; teeth with no periodontal disease; and teeth with adequate root canal treatments on the basis of the apical terminus (from 0 to 1 mm short of the apex), homogeneous fillings (no voids) and tapered canal shape, as determined both radiographically and by CBCT analysis. The study protocol was approved by the Ethics Committee of the Estácio de Sá University and written informed consent was obtained from all individuals.
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