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

This study aims to assess and compare the microbiome of paired root apices and periapical lesions from cases with failed endodontic treatment and to associate the microbiome and bacterial metabolic pathways in both sites with asymptomatic apical periodontitis (AAP) and symptomatic apical periodontitis (SAP), using next‐generation sequencing (NGS). In the study results, a higher alpha‐diversity was observed in the periapical lesions, although no global differences in the community composition between the two sites were found, the most prevalent genera being Fusobacterium, Porphyromonas and Streptococcus. Prevotella, Clostridiales_vadinBB60_group, Bosea, Phreatobacter, Afipia and Xanthobacteriaceae_unclassified were enriched in SAP samples, while Pseudopropionibacterium, Campylobacter and Peptoniphilus were significantly more abundant in AAP cases. Metabolic pathways involved in the amino acid metabolism or degradation and flagellum assembly were more abundant in SAP samples, whereas glucose metabolism‐related pathways were associated with AAP. In conclusion, the bacterial community composition was similar in the apices and periapical lesions. However, the microbiome was different in AAP and SAP samples, with gram‐negative bacteria showing higher relative abundances in SAP cases. An association was observed between amino acid degradation and flagellum assembly pathways and the development of tenderness to percussion or palpation.