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A three dimensional analysis of the effect of irrigant flow velocity on endodontic biofilms Mirdad, Lujain


Introduction: Irrigation of the root canal system is an essential part of disinfection during root canal treatment. Some irrigants have the ability to dissolve or detach the biofilm from the dentin surface as well as kill residual bacteria. Several chemical and physical parameters affect the effectiveness of the irrigation process. Aim: The primary aim of this study is to investigate the effect of irrigation flow velocity on the biovolume of the biofilm and antimicrobial effect against biofilm microbes. Materials and methods: Hydroxyapatite discs coated with type I collagen were used as the biofilm substrate. Mixed supra- and sub-gingival plaque was collected from a single donor and suspended in Brain Heart Infusion broth (BHI). The discs were placed in 24-well tissue culture plates containing BHI-plaque suspension. They were then incubated under anaerobic conditions for three weeks. BHI medium was replaced with a fresh solution once a week. After three weeks of biofilm growth, the discs were placed in a CDC Biofilm reactor placed on a magnetic stir plate. The speed settings used were 60 rpm and 200 rpm both for 30 and 60 seconds. 0.1 % Sodium hypochlorite solutions and sterilized spring water were utilized for the experiment. Control samples were not subjected to any treatment. After treatment, all discs were stained with a viability stain and assessed under a confocal laser scanning microscope. The total biofilm volume and percentage of dead bacteria were calculated using the Bioimage L software. Results: Sodium hypochlorite NaOCl at 200 rpm was significantly more effective than control groups in reducing biofilm volume and killing biofilm bacteria. At slower flow velocity (60 rpm), there was no difference when compared to the negative control groups not subjected to any treatment. Multivariate analysis results revealed that irrigant type and flow velocity had a significant effect on reducing biofilm volume and killing biofilm bacteria. Exposure time influenced the biofilm volume only (p< 0.001). Conclusion: Irrigation flow velocity is a significant factor in the antimicrobial effectiveness of irrigation procedures. Our findings demonstrate is important to consider irrigation fluid dynamics when studying the antimicrobial effects of different irrigants in the future.

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