OR34 - Level of E. Faecalis Biofilm Formation in Different Segments of Root Canal Space in Vitro -- an SEM Study

Abstract: Objective: To determine the level of Enterococcus faecalis (Ef) biofilm formation in different segments of root canal space in extracted teeth before disinfection studies. Methods: Five single-canal incisors were instrumented to size 40/.04 with NaOCl/EDTA irrigation, then autoclaved. Four teeth were filled with growing Ef and one tooth served as a negative control. Each tooth was placed in a 15-mL tube containing BHI (brain heart infusion) broth and incubated at 37°C. BHI was changed twice a week. After ~4 weeks, all teeth were vertically split and fixed/processed for Scanning Electron Microscopy (SEM). Semi-qualitative analysis was performed by scoring the level of Ef colonization and biofilm formation in the coronal, middle, and apical thirds of the canal. Three calibrated evaluators scored SEM images from 0-5, with 5 being the heaviest biofilm formation. Scores were averaged and subjected to ANOVA. Results: No bacteria were observed in the control tooth; however, smear layer or crystal-like deposits were seen on the canal wall, especially in the apical third. In test teeth, Ef colonization was not uniform. Some areas contained heavy biofilm throughout the canal space while other areas had little bacterial colonization. Statistically, there was minor significant difference in the coronal, middle, or apical third within some test teeth or between some test teeth (p < 0.05 or 0.001), in the level of colonization/biofilm formation. Conclusion: SEM studies of in vitro canal disinfection using Ef models should recognize that uneven colonization/biofilm formation within and between samples may misrepresent actual canal disinfection efficiency.