Department of Dentistry, School of Health Sciences, University of Brasília, Brasília, Distrito Federal, Brazil.
Division of Restorative Dentistry, School of Dentistry, University of Leeds, Leeds, United Kingdom.
J Endod. 2022 Jul;48(7):855-863. doi: 10.1016/j.joen.2022.03.008. Epub 2022 Apr 4.
Secondary infections may be linked to the presence of residual microorganisms within dental root canals. The purpose of this study was to investigate the bacterial composition of primary and secondary root canal infections before and after chemomechanical treatment.
Samples were collected before chemomechanical preparation (S1) and before obturation (S2) from 19 subjects (10 primary and 9 secondary infections). DNA was extracted, and the V3/V4 region of the 16S ribosomal RNA gene was amplified using the 347 F/803R primers and paired-end sequenced using the MiSeq (Illumina, San Diego, CA) instrument.
Sequencing analysis yielded partial 16S ribosomal RNA gene sequences that were taxonomically classified into 10 phyla and 143 genera. The most prevalent phyla in the S1 and S2 samples were Firmicutes and Bacteroides; however, when comparing between sample groups, Proteobacteria seem to have been enriched in secondary infections. The dominant genera in the primary S1 samples were Bacillus, Streptococcus, and Prevotella, whereas Bacillus, Streptococcus, and Selenomonas dominated the secondary infection S1 samples. Bacillus and Marinilactibacillus were the most dominant genera in the primary and secondary S2 samples. The mean number of operational taxonomic units per sample was 32,656 (±12,124 SD) and 37,113 (±16,994 SD) in the S1 and S2 samples, respectively. Alpha and beta diversities presented the same pattern within samples from both groups.
Great interindividual variations in the bacterial composition of the root canal biofilms were observed. There was no difference in the bacterial composition before and after treatment, although some genera survived and seem to be part of a residual microbiome. Our findings revealed a high diversity of the bacterial communities present in root canal infections after chemomechanical treatment, although the majority of the taxa detected were in low abundance.
继发性感染可能与牙根管内残留微生物的存在有关。本研究旨在调查化学机械治疗前后原发性和继发性根管感染的细菌组成。
从 19 名受试者（10 名原发性和 9 名继发性感染）中采集化学机械预备前（S1）和封闭前（S2）的样本。使用 347F/803R 引物扩增 16S 核糖体 RNA 基因的 V3/V4 区，并使用 MiSeq（Illumina，圣地亚哥，CA）仪器进行配对末端测序。
测序分析产生了部分 16S 核糖体 RNA 基因序列，这些序列在分类上分为 10 个门和 143 个属。S1 和 S2 样本中最常见的门是厚壁菌门和拟杆菌门；然而，在比较样本组时，变形菌似乎在继发性感染中富集。原发性 S1 样本中的优势属为芽孢杆菌属、链球菌属和普雷沃氏菌属，而芽孢杆菌属、链球菌属和硒单胞菌属则是继发性感染 S1 样本的优势属。芽孢杆菌属和 Marinilactibacillus 是原发性和继发性 S2 样本中最主要的属。S1 和 S2 样本中每个样本的操作分类单元数平均值分别为 32656（±12124SD）和 37113（±16994SD）。两组样本的 alpha 和 beta 多样性呈现相同的模式。
观察到根管生物膜的细菌组成存在很大的个体间差异。尽管一些属存活下来，似乎是残留微生物组的一部分，但治疗前后的细菌组成没有差异。我们的研究结果表明，化学机械治疗后根管感染中存在高度多样性的细菌群落，尽管检测到的大多数分类群丰度较低。
