Bacterial analysis of combined periodontal-endodontic lesions using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE)

Abstract

Objective To compare the bacterial community profiles present in periodontium and root canals of the same tooth diagnosed as combined periodontal-endodontic lesions by using denaturing gradient gel electrophoresis (DGGE).Methods Samples were collected from 13 extracted teeth with advanced periodontitis,endodontic samples from root tip 1/3 root canal,and periodontal samples from the corresponding neighboring periodontium.Genomic DNA was collected for the following universal bacterial primersPCR.The PCR products were then loaded on the DGGE gels to gain separate bands.The typical DGGE bands were excised,PCR-cloned and sequenced.Results The number of bands,which was indicative of the number of bacterial species,was compared intra-group (periodontal and pulpal specimen from the same tooth).The difference was statistically significant (P＜0.01),but there was no positive correlation between them.The similarity (Dice Coefficient) between them was 13.1％-62.5％.Taxa identified through BLAST (≥98％ identity) were Campylobacter,Fusobacterium,Neisseria,et al in the periodontium,and Mogibacterium,Corynebacterium,Actinomyces,et al in the root canals.Conclusion Common bacteria existed between them,but not all of the periodontal bacteria would appear in neighboring root canal; and the bacteria in the root canal are not completely from neighboring periodontal tissue.The original bacteria in the root canals may resuscitate and enrich the bacterial community.In combined periodontal-endodontic lesions (periodontal source),it is probable that new species existed to be confirmed either in the periodontium or in the root canal. Key words: Combined periodontal-endodontic lesions; Denaturing gradient gel electrophoresis; 16S rDNA; Bacteria