Influence of endodontic chemical treatment on Enterococcus faecalis adherence to collagen studied with laser scanning confocal microscopy and optical tweezers: a preliminary study.

Failure of endodontic treatment is commonly associated with the presence of Enterococcus faecalis. Studies have highlighted that E. faecalis can form a calcified biofilm in tough environmental conditions, such as within root canals. The aims of this study were to investigate the effects of chemicals used in root-canal disinfection on the adherence of E. faecalis to collagen, as well as to estimate the force of adhesion between E. faecalis and collagen after such treatment. The number of adhering bacteria after chemical treatment was determined using confocal laser scanning microscopy-based adherence assay. It was found that the calcium hydroxide-treated group had a statistically significant (p=0.05) increase in the population of bacteria adhering. The adhesion force between bacteria and collagen of the treatment group with the highest number of bacteria adhering was determined by using optical tweezers (1064 nm) and Equipartitition theorem-based stiffness measurements. The presence of calcium hydroxide was found to significantly increase the bacterium-collagen adhesion force. These experiments highlighted the potential advantage of using optical tweezers to study bacteria-substrate interactions. The findings from the present study suggests that the presence of calcium hydroxide increased the adhesion force and adherence of E. faecalis to type-I collagen.