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Updated: May 1, 2026
Concurrent Quantification of Cellular and Extracellular Components of Biofilms
Published on: December 10, 2013
Effect of long-term exposure to endodontic disinfecting solutions on young and old Enterococcus faecalis biofilms in
Tianfeng Du1, Zhejun Wang2, Ya Shen3
1Department of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia, Canada.
Introduction:
The purpose of this study was to evaluate the antimicrobial activity on Enterococcus faecalis biofilms in dentin canals of short-term and long-term exposure to different endodontic disinfecting solutions by using a dentin infection model and confocal laser scanning microscopy.
Methods:
Dentinal tubules in semi-cylindrical dentin blocks were filled with E. faecalis by centrifugation and incubated to form 1-day-old and 3-week-old biofilms. The young and mature biofilms in dentin were subjected to sterile water, 2% chlorhexidine, 2% sodium hypochlorite (NaOCl), and 6% NaOCl for 3, 10, and 30 minutes. After treatments, the proportion of bacteria killed by the disinfectants was analyzed by confocal laser scanning microscopy by using LIVE/DEAD bacterial viability stain.
Results:
The proportion of killed bacteria was lower after 3 minutes than after 10 and 30 minutes of exposure to the disinfecting agents (P < .05). The killing of bacteria in the E. faecalis biofilms was fastest during the first 3 minutes and slowed down greatly after 10 minutes. Six percent NaOCl was the most effective antibacterial solution against both the 1-day-old and 3-week-old biofilms (P < .05). No significant difference in bacterial killing was detected between 2% chlorhexidine and 2% NaOCl (P > .05). Significantly more cells were killed in young biofilms than in old biofilms in all groups (P < .05).
Conclusions:
The killing of bacteria in infected dentin by disinfecting solutions is time-dependent. However, little additional killing is obtained after the first 10 minutes of exposure.
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