Methods: Forty-four extracted human teeth were decoronated and instrumented in a uniform manner with using 0.06 tapered K3 NiTi Rotary files to size 45 and randomly assigned to either 3 experimental (n=12) or positive/negative control groups (n=4). A dual-chamber anaerobic leakage model was used for the leakage evaluation. After turbidity occurred in the lower chamber during 35 days observation period, 1mL samples were collected and type of the bacteria leaked was assessed with PCR assay. DNA extracted from the specimens was amplified by polymerase chain reaction, which yielded a specific segment of E. faecalis's and F. nucleatum's DNA. Visualisation of the PCR product was done using 1.5% agrose gel according to a standard protocol.
Results: Non-leaked specimens were highest for RealSeal sealer (5/12), only one sample left in AH Plus group (11/12) and non for MetaSEAL group (12/12) at the end of 35 day observation period. All bacterial samples that have been assigned to PCR test were tested positive for E. faecalis. On the other hand, only few samples were tested positive for F. nucleatum. These were 3 samples from each of the RealSeal and the MetaSEAL groups.
Conclusion: The resistance of root canal fillings to bacterial entrance may vary according to the type of the bacterial marker used during bacterial leakage assessment. E. faecalis's quick penetration through root canal fillings might explain its prevalence in failed endodontic cases.