Molecular Fingerprinting Reveals the Presence of Unique Communities Associated with Paired Samples of Root Canals and Acute Apical Abscesses

Introduction: Acute primary endodontic infections are polymicrobial infections that affect both the root canal (RC) system and apical tissues. It is known that these communities cannot be detected by conventional culturing methods. The aim of this study was to examine the profile of microbial communities in necrotic RCs and acute apical abscesses (AAAs) using an open-ended molecular approach to compare the diversity and composition of the microbiota of these two communities. Methods: Paired samples of RC and PA exudates were collected from 20 subjects and analyzed by terminal restriction fragment length polymorphism (t-RFLP). The number of peaks, the peak areas, and the community diversity were compared between RCs and PAs. The similarity of the microbial profile of each pair of RCs and PAs was assessed by computing the number of shared peaks and the Bray-Curtis Similarity Index. Results: A total of 103 and 75.5 unique fragments (t-RFs) were detected in RC and PA samples, respectively. RCs and PAs were not different in the number of species or in the community diversity; however, very few species were shared between RC and PA samples. No single t-RF fragment was detected in all samples, and the majority was detected in only one sample. Low diversity of species was observed in the RCs of smokers. Subjects with previous pain showed fewer species and greater community diversity. Conclusion: The microbial profiles of the RC and PA communities are distinct and diverged between all subjects, suggesting that acute endodontic infections are microbiologically heterogeneous. (J Endod 2010;36:1475-1479)