title: Investigation of cultivable bacteria isolated from longstanding retreatment-resistant lesions of teeth with apical periodontitis.
abstract: BACKGROUND
  The objective of this research was 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.
  
  
  METHODS
  Twenty persistent apical lesions associated with well-performed endodontic retreatment were collected. Tissue samples were processed through culture techniques including serial dilution, plating, aerobic and anaerobic incubation, and biochemical tests for microbial identification followed by histopathological diagnosis.
  
  
  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 gram-positive 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.
  
  
  CONCLUSIONS
  In conclusion, 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.
authors.affiliation: Endodontic Division, Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Piracicaba, São Paulo, Brazil.
authors.forename: Fernanda G C
authors.initials: FG
authors.lastname: Signoretti
authors.forename: Brenda P F A
authors.initials: BP
authors.lastname: Gomes
authors.forename: Francisco
authors.initials: F
authors.lastname: Montagner
authors.forename: Rogério C
authors.initials: RC
authors.lastname: Jacinto
mesh_terms: D000293:Adolescent; D000328:Adult; D000332:Aerobiosis; D000368:Aged; D000693:Anaerobiosis; D001431:Bacteriological Techniques; D003475:Curettage / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D058834:Gemella / Q000302:isolation & purification; D006094:Gram-Positive Bacteria / Q000302:isolation & purification*; D016908:Gram-Positive Bacterial Infections / Q000628:therapy; D006801:Humans; D008297:Male; D050296:Microbial Viability; D008875:Middle Aged; D010484:Periapical Granuloma / Q000382:microbiology / Q000628:therapy; D010485:Periapical Periodontitis / Q000382:microbiology* / Q000628:therapy; D011425:Propionibacterium acnes / Q000302:isolation & purification; D011842:Radicular Cyst / Q000382:microbiology / Q000628:therapy; D012008:Recurrence; D019233:Retreatment; D012390:Root Canal Therapy / Q000379:methods; D019553:Tooth, Nonvital / Q000382:microbiology; D017211:Treatment Failure; D055815:Young Adult
keywords: Apical periodontitis; apical surgery; endodontic failure; endodontic outcome; nonsurgical retreatment