Bacteriological conditions of the apical root canal system of teeth with and without post-treatment apical periodontitis. A correlative multi-analytical approach

Introduction This study used a correlative multi-analytical approach to investigate the bacteriological conditions in the apical root canal system of treated teeth with or without apical periodontitis, and their correlation with the technical quality of the previous root canal obturation and the presence and volume of apical periodontitis lesion. Methods Root apices were obtained from recently extracted root canal-treated teeth with (n=23) and without (n=22) apical periodontitis lesion, as demonstrated by cone-beam computed tomography (CBCT) examination. The root apexes were sectioned and subjected to micro-computed tomography (micro-CT) scanning. The specimens were cryopulverized and DNA extracted from the powder was used as template in real-time polymerase chain reaction assays to quantify total bacteria and members of the Streptococcus genus and Actinobacteria phylum. The bacteriological findings were compared between the two groups and also evaluated for associations with CBCT and micro-CT data. Results Bacteria were detected in all apical canal samples, except one. The mean counts of total bacteria, streptococci and actinobacteria did not differ significantly between teeth with or without apical periodontitis (p>0.05). Streptococcus levels were significantly lower by 80% in the apical canals of teeth with small lesions compared with those without lesions (p<0.05). The limit of filling >2 mm short was significantly associated with more total bacterial counts compared with canals filled 0 to 2 mm short (p<0.05). An adequate coronal restoration was significantly associated with lesser counts of Streptococcus (p<0.05). Conclusions Comparable bacterial loads were observed in the apical canal system of treated teeth with and without apical periodontitis, suggesting that factors other than only the total bacterial levels may also influence the development and progression of apical periodontitis. Bacteria were found in the apical canal in virtually all cases, with a high prevalence of streptococci and actinobacteria. Streptococci counts were significantly higher in the apical canal of teeth with inadequate restorations and teeth with no lesions. Underfilled canals showed higher bacterial counts.