[Microbial communities in extraradicular infections of post-treatment apical periodontitis without or with sinus tracts].

[OBJECTIVE] To compare the composition and structure of extraradicular bacterial communities in periapical lesions of teeth with post-treatment apical periodontitis (PoAP) between cases with and without sinus tracts.

[METHODS] Patients requiring apical surgery were recruited from the Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology. Periapical lesion samples were collected from teeth with sinus tracts and without sinus tracts during apical microsurgery. The remaining lesion samples were submitted for pathological examination. Following the extraction of the bacterial DNA, the V3-V4 region of the bacterial 16S rRNA gene was subjected to high-throughput sequencing using Illumina NovaSeq 6000. Bioinformatics analysis was performed using QIIME2 software. α diversity indices (Shannon, Simpson, Chao1) were calculated, and intergroup differences were analyzed using Wilcoxon test. β diversity was assessed by principal coordinate analysis based on Weighted Unifrac test, and community composition differences were analyzed with permutational multivariate analysis of variance (PERMANOVA). Differences in relative abundance between the groups were compared using the Wilcoxon test, followed by Benjamini-Hochberg false discovery rate (FDR) correction to convert value to value.

[RESULTS] A total of 66 subjects were enrolled, including 21 male and 45 female patients, with a mean age of (33.91±9.16) years. Three subjects each had two teeth enrolled. In total, 69 teeth were included. These teeth included 47 cases without sinus tracts and 22 cases with sinus tracts. No significant differences were observed between the two groups in the distribution of obturation quality or pathological types (>0.05). No statistically significant differences were found in α diversity indices between the two groups (>0.05). However, β diversity analysis revealed a significant difference between the two groups (=0.008). At the phylum level, the relative abundance of Bacteroidota was significantly higher in the group with sinus tracts (16.98% 9.22%, < 0.01), while the relative abundance of Pseudomonadota was significantly lower in the group with sinus tracts (30.70% 42.19%, < 0.05). At the genus level, , , , , and were significantly enriched in the group with sinus tracts ( < 0.05), whereas was more abundant in the group without sinus tracts ( < 0.05).

[CONCLUSION] The extraradicular bacterial community structure significantly differs between PoAP with and without sinus tracts. , , , , and may be associated with the formation and persistence of sinus tracts.