Assessment of the microbiota in root canals of human primary teeth by checkerboard DNA-DNA hybridization.

Purpose: The purpose of this study was to evaluate in vivo the prevalence of microorganisms in root canals of human primary teeth, by checkerboard DNA-DNA hybridization.

Methods: Fifty-five root canals of primary teeth with irreversible pulpitis (group 1) and 51 root canals of teeth with pulp necrosis and apical periodontitis (group 2) were selected. Microbiological samples were collected and submitted to checkerboard DNA-DNA hybridization using 34 genomic DNA probes. The results were analyzed statistically by Mann-Whitney U-test at a 5% significance level.

Results: The most prevalent species in group 1 were: (1) Campylobacter rectus (87%); (2) Gemella morbilorum (78%); (3) Streptococcus gordonii (71%); (4) Capnocytophaga ochracea (69%); (5) Treponema denticola (58%); and (6) Streptococcus intermedius (49%). The most prevalent species in group 2 were: (1) C. rectus (90%); (2) T. denticola (88%); (3) S. intermedius (77%); (4) G. morbilorum (73%); (5) Streptococcus oralis (67%); (6) C. ochracea (63%); (7) S. gordonii (55%); (8) Streptococcus mitis (51%); and (9) Leptotrichia buccalis (51%). Except for Peptostreptococcus micros and Actinomyces israelii, the most prevalent bacterial strains in the root canals with apical periodontitis were also those found in larger numbers (P<.05). Groups 1 and 2 differed significantly (P<.05) regarding the total number of bacterial cells detected in the root canal samples, with group 2 showing remarkably larger bacterial cell numbers.

Conclusions: Root canals of primary teeth have a great bacterial diversity, characterizing a polymicrobial endodontic infection with presence of: (1) anaerobic and facultative micro organisms; (2) black-pigmented rods; and (3) streptococci. A large number of anaerobic species were detected in teeth with necrotic pulp and apical periodontitis, and a significantly smaller number of bacterial cells were found in teeth with irreversible pulpitis.