In vivo antimicrobial effects of endodontic treatment procedures as assessed by molecular microbiologic techniques.

INTRODUCTION: This culture-independent molecular microbiology study evaluated the antimicrobial effects of chemomechanical preparation supplemented by intracanal medication during treatment of teeth with apical periodontitis.
METHODS: Samples were taken from 24 necrotic root canals at the baseline (S1), after chemomechanical preparation by using 2.5% NaOCl as the irrigant (S2), and after a 7-day interappointment medication with calcium hydroxide paste in either glycerin (CHG) or camphorated paramonochlorophenol/glycerin (CHPG) (S3). Bacterial, archaeal, and fungal presence was evaluated by polymerase chain reaction (PCR), and bacterial identifications were performed by a closed-ended reverse-capture checkerboard approach targeting 28 candidate endodontic pathogens.
RESULTS: All S1 samples were positive for bacteria but negative for both archaea and fungi. Treatment procedures were highly effective in reducing the bacterial levels and number of taxa. Overall, 46% of S2 samples and 62.5% of S3 samples were PCR-negative for bacteria. Specifically, S2 and S3 samples yielded negative PCR results in 50% and 58% of the canals in the CHG group and in 42% and 67% of the canals in the CHPG group, respectively. Except for comparisons with S1 samples, no other statistically significant differences were observed for intragroup and intergroup comparisons involving S2 and S3. Several taxa were still found in S2 and S3 samples, and the most prevalent were Propionibacterium acnes and Streptococcus species.
CONCLUSIONS: Bacterial levels and number of taxa were substantially reduced after chemomechanical preparation and intracanal medication. However, presence of detectable levels of persisting bacteria in many cases indicates that the search for more effective antimicrobial treatment strategies should be stimulated.