•Purpose: To investigate the presence of viable bacteria in tissue samples from persistent apical lesions and to correlate the microbiological findings with the histopathological diagnosis of the lesion.
•N=20 persistent apical lesions associated with well-performed endodontic retreatment.
• Tissue samples were collected after endo surgery and processed through culture techniques including serial dilution, plating ,aerobic and anaerobic incubation, and biochemical tests for microbial identification followed by histopathological diagnosis.
•Most highlighted Results:
•Cysts were more frequently diagnosed (13/20).
•Strict anaerobic species predominated in both cysts (80.4% of the species detected) and granulomas (65% of the species detected).
•Viable grampositive bacteria were frequently recovered from apical lesions (cysts = 70.6%, granulomas = 84.4%)
•Gemella morbillorum and Propionibacterium acnes were the most frequently recovered species from cysts and granulomas, respectively.
•At least 1 gram-positive bacterial species was present in almost every sample (cysts = 12/13, granulomas = 7/7).
•No significant correlation was found between histologic findings and bacterial species.
Although cysts were more frequent than granulomas in cases of failure of endodontic retreatment, bacteria were isolated from both types of lesions, with a predominance of gram positive species, suggesting that these species can survive outside the root canal and might be related to the persistence of the pathological process even after accurate endodontic retreatment.