All swab samples were negative, indicating a disinfected operation field.
All 58 samples contained cultivable microorganisms. The median number of CFU mLx1 was 8 x104 (range 50-3 x107 CFU mLx1) per sample. The number of species per canal varied between 4 and 7 (mean 5.1). Of the isolated species, 87% were strictly anaerobic. The most prevalent bacterial species were P. intermedia, P. micros and A. odontolyticus, present in, respectively, 33, 29 and 19% of the cultured canals (Table 1, Fig.1). P. intermedia and P. micros were present in significantly more samples than any of the other species (P < 0.05). A. odontolyticus was present in significantly more samples than most species except for F. nucleatum, P. intermedia, Capnocytophaga spp., Eubacterium lentum, Propionobacterium acnes and P. micros.
A total of 81 combinations of bacterial species were tested with the Fisherâ€™s exact test. For four microbial combinations, the null hypothesis had to be rejected and therefore indicated a positive association between two species. Table 2 shows all four combinations that had an Odds ratio >2, indicating a positive relationship. Negative relationships were not found.
Table 1. Prevalence of bacterial species in 58 root canals.
* Prevotella intermedia and Peptostreptococcus micros were significantly more present than all other species (P < 0.05).
** Actinomyces odontolyticus was significantly more present than all except Fusobacterium nucleatum, Prevotella intermedia, Capnocytophaga spp., Eubacteriumlentum, Peptostreptococcusmicros and Propionibacteriumacnes (P< 0.05).
Figure 1. Percentages of isolates from 58 root canals.
OR, Odds ratio.
CI, confidence interval.