(PR117) Removal of E. Faecalis Biofilm in Root Canal by ErCr:YSGG Biolase -- a Pilot Study

Objective: To determine the level of E. faecalis biofilm removal by NaOCl combined with ErCr:YSGG Biolase in extracted human teeth in vitro.

Methods: Six single-canal teeth were instrumented to size 40/.04 with NaOCl/EDTA irrigation, then autoclaved. All teeth were filled with growing E. faecalis and incubated in brain heart infusion broth at 37°C for ~6 weeks. Teeth were randomly divided into three groups and subjected to 6.25% NaOCl/Biolase disinfection. Canal contents were collected before and after disinfection and then subjected to MTT assays. Group I, II, III received one round (4x10-sec cycles), three rounds and six rounds respectively of standard Biolase canal disinfection irrigated with 6.25% NaOCl. Teeth were then fixed and vertically split for scanning electron microscopy (SEM). Semi-quantitative analysis was performed by scoring (0-5, 5 being heaviest) the level of remaining E. faecalis and/or presence of smear layer in the canal. Data analyzed by ANOVA.

Results: MTT showed 99% E. faecalis reduction in Groups I&II. Group III reading was too low to measure. Smear layer or crystal-like deposits were seen throughout the canal walls under SEM analysis. Intact E. faecalis were not observed in most samples except a few in Group III, although their vitality cannot be assessed. Possible intact E. faecalis embedded under the heavy accumulation of smear layer in certain areas cannot be determined. No statistical difference of smear layer levels between groups (p>0.05) was found.

Conclusion: Combination of 6.25% NaOCl and Biolase can reduce heavy E. faecalis colonies in the canal by 99%, but are not capable of removing smear layers.