Bacteria Community Study of Combined Periodontal-Endodontic Lesions Using Denaturing Gradient Gel Electrophoresis and Sequencing Analysis

Background: The entire microbial population and predominant microflora of root canals (RCs) and adjacent periodontal pockets (PPs) from teeth with combined periodontal-endodontic lesions were determined and compared. Methods: Pooled RC and PP samples were collected from the molars of 20 patients diagnosed with combined periodontal-endodontic lesions. DNA was extracted for polymerase chain reaction-based denaturing gradient gel electrophoresis (PCR-DGGE), cloning, and sequence analysis. A coefficient of similarity (Cs) was used to determine the similarity of the bacterial profiles from RCs and PPs. Results: Significantly fewer bands were produced by PCR-DGGE from RCs (5.9 +/- 1.7) than from PPs (8.0 +/- 1.8) (P <0.001). The average Cs of the RC and PP samples was 93.81% +/- 10.26%. Overall, 60 genera/species were identified by sequencing. Of these, the predominant genera in RCs were Porphyromonas sp. (13.9%), Filifactor sp. (12.5%), and Parvimonas sp. (11.1%), similar to the genera obtained from PP samples. In total, 43 genera/species were common to the RC and PP samples. The most prevalent bacteria in both the RC and PP samples were (in descending order) Filifactor alocis, Parvimonas micra, Porphyromonas gingivalis, and Tannerella forsythia. Conclusions: The high similarity in the sets of organisms present in both RC and PP samples in this study suggests that the pocket could be a source of RC infection. The data also demonstrate that combined periodontal-endodontic lesions consist of a diverse and complex microbial community.