Mohmmed, Saifalarab; (2017) Investigations into the removal and destruction of bacterial biofilms by sodium hypochlorite irrigant delivered into an in vitro model. Doctoral thesis , UCL (University College London).

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Abstract

AIMS: To investigate the influence of canal design (closed, open), irrigant concentration, agitation, canal complexity, and biofilm type on the efficacy of sodium hypochlorite to remove biofilm. To examine the extent of biofilm destruction following irrigation protocols. METHODOLOGY: Standardized in vitro models were developed (Endo-Vu block, flow cell, and 3D printing root canal models). The canal consisted of two halves of an 18 mm length, size 30 and taper 0.06, with or without a lateral canal of 3 mm length, and 0.3 mm diameter. Biofilms were grown for 10 days, and stained using crystal violet. The model was attached to an apparatus and observed under a fluorescent microscope. Following 60 s of 9 mL NaOCl irrigation using syringe and needle, the irrigant was either left stagnant or agitated using gutta-percha, sonic and ultrasonic methods for 30 s. Images were captured every second using an external camera. The residual biofilm percentages were measured using image analysis software. The SPSS software was used for statistical analysis. The residual biofilms were observed using confocal laser scanning, scanning electron, and transmission electron microscope. RESULTS: The removal of biofilm by NaOCl was more extensive in the open than in the closed canal. The concentration and extent of the needle had an influence on the amount of the residual biofilm. Ultrasonic agitation increased the biofilm removal from the main canal (90.13%) and lateral canal (66.76%). Extensive destruction of residual biofilm was observed in the ultrasonic groups. More residual multi-species biofilm than single species biofilm was identified (p = 0.001). CONCLUSION: The 3D-printing model provides a reliable method to investigate irrigation procedure. The closed canal adversely affect the efficacy of NaOCl. Concentration and position of the needle affect the efficacy of NaOCl. The results recommend the ultrasonic method for NaOCl agitation. The multi-species biofilm was more resistant than the single species biofilm.

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