Microbial Communities in the Extraradicular and Intraradicular Infections Associated With Persistent Apical Periodontitis

Abstract

Microorganisms in the complex root canal system and the extraradicular regions, including the periapical lesions and extraradicular biofilm may cause root canal treatment failures. However, few studies described the difference between the intraradicular and extraradicular infections from the same tooth associated with persistent apical periodontitis. This study aimed to characterize the microbiome present in the root canal, extraradicular biofilm, and periapical lesions associated with persistent apical periodontitis. The microbial communities in the root canal, extraradicular biofilm, and periapical lesions were investigated by Illumina high-throughput sequencing using Illumina Hiseq 2500 platform. The dominant phyla in the extraradicular and intraradicular infections associated with persistent apical periodontitis were Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria, and the genera Fusobacterium, Morganella, Porphyromonas, Streptococcus, and Bifidobacterium dominated across all samples. Although extraradicular infection sites showed higher OTU richness and β-diversity compared to intraradicular samples, the occurrence of sinus tract rather than the sampling sites demarcated the microbial communities in the infections associated with persistent apical periodontitis. PERMANOVA analysis confirmed that the samples with or without sinus tracts contained significantly different microbial communities. Porphyromonas, Eubacterium, Treponema, and Phocaeicola were found in significantly higher levels with sinus tracts, whilst Microbacterium and Enterococcus were more abundant in samples without sinus tracts. In conclusion, diverse bacteria were detected in both intraradicular and extraradicular infections associated with persistent apical periodontitis, which might be influenced by the occurrence of the sinus tract. The results may provide new insight into the pathogenesis of persistent apical periodontitis.

Microbiome in paired root apices and periapical lesions and its association with clinical signs in persistent apical periodontitis using next‐generation sequencing

“…Two out of 38 lesions (5.3%) were discarded because of the low amount of DNA in the samples, meaning that some periapical lesions would be free of microorganisms, as previously reported (Noguchi et al, 2005; Saber et al, 2012; Sun et al, 2022; Sunde et al, 2002). Paired‐end sequencing of 16 S rRNA gave an average of 19 186 reads per sample and a coverage higher than 97% in all samples, confirming an adequate sequencing depth.…”

“…However, once the microorganisms reach the periapical tissues, they must adapt to new ecological conditions, for example, a higher nutrient availability as compared to the treated root canal, less oxygen and the action of the host immune cells. To date, there is little evidence of the microbial correlation in paired samples – including apices and periapical lesions – or contradictory results (Pereira et al, 2017; Subramanian & Mickel, 2009; Sun et al, 2022). A deeper knowledge of the intraradicular and extraradicular infection in the sustained disease would shed light on the reasons behind failure of the root canal treatment.…”

Macrophages in periapical lesions: Potential roles and future directions

“…Hou et al ( 39 ) found that the abundance of Porphyromonas gingivalis , Phocaeicola abscessus , Campylobacter showae , and Tannerella forsythia was higher among patients with obvious symptoms than in those without, suggesting that the number and species of microbe might affect the outcome of PLs. Sun et al ( 40 ) found that the dominant bacteria isolated from extraradicular and intraradicular samples from persistent APs were quite different, which suggests that different bacteria play different roles in the pathogenesis of persistent PLs. Considering the fundamental roles of bacteria in the progression of PLs, in this section we summarize the functions of oral bacteria, such as Enterococcus faecalis and P. gingivalis , in the polarization of macrophages ( 41 , 42 ).…”

Low-Diversity Microbiota in Apical Periodontitis and High Blood Pressure Are Signatures of the Severity of Apical Lesions in Humans

“…Here, we decipher the potential mechanisms of this phenomenon. We therefore hypothesize that the virulence of endodontic microbiota and its diversity are major regulators of severity of AP, as suggested for chronic periapical lesions [ 12 ]. In addition, high blood pressure could be associated with the severity of AP [ 13 , 14 ].…”