Fluid Dynamics and Biofilm Removal Generated by Syringe-delivered and 2 Ultrasonic-assisted Irrigation Methods: A Novel Experimental Approach.
BACKGROUND
Thorough understanding of fluid dynamics in root canal irrigation and corresponding antibiofilm capacity will support improved disinfection strategies. This study aimed to develop a standardized, simulated root canal model that allows real-time analysis of fluid/irrigation dynamics and its correlation with biofilm elimination.


METHODS
A maxillary incisor with an instrumented root canal was imaged with micro-computed tomography. The canal volume was reconstructed in 3 dimensions and replicated in soft lithography-based models microfabricated from polyethylene glycol-modified polydimethylsiloxane. Canals were irrigated by using a syringe (SI) and 2 ultrasonic-assisted methods, intermittent (IUAI) and continuous (CUAI). Real-time fluid movement within the apical 3 mm of canals was imaged by using microparticle image velocimetry. In similar models, canals were inoculated with Enterococcus faecalis to grow 3-week-old biofilms. Biofilm reduction by irrigation with SI, CUAI, and IUAI was assessed by using a crystal violet assay and compared with an untreated control.


RESULTS
SI generated higher velocity and shear stress in the apical 1-2 mm than 0-1 and 2-3 mm. IUAI generated consistently low shear stress in the apical 3 mm. CUAI generated consistently high levels of velocity and shear stress; it was the highest of the groups in the apical 0-1 and 2-3 mm. Biofilm was significantly reduced compared with the control only by CUAI (two-sample permutation test, P = .005).


CONCLUSIONS
CUAI exhibited the highest mechanical effects of fluid flow in the apical 3 mm, which correlated with significant biofilm reduction. The soft lithography-based models provided a novel model/method for study of correlations between fluid dynamics and the antibiofilm capacity of root canal irrigation methods.
Discipline of Endodontics, University of Toronto, Toronto, Ontario, Canada.
Gillian
G
Layton
Department of Mechanical Engineering, McMaster University, Hamilton, Ontario, Canada.
Wen-I
WI
Wu
Department of Mechanical Engineering, McMaster University, Hamilton, Ontario, Canada.
Ponnambalam Ravi
PR
Selvaganapathy
Discipline of Endodontics, University of Toronto, Toronto, Ontario, Canada.
Shimon
S
Friedman
Discipline of Endodontics, University of Toronto, Toronto, Ontario, Canada. Electronic address: akishen@gmail.com.
Anil
A
Kishen
D018441:Biofilms / Q000187:drug effects*; D006801:Humans; D007180:Incisor / Q000187:drug effects / Q000382:microbiology; D012388:Root Canal Irrigants / Q000008:administration & dosage*; D018915:Root Canal Preparation / Q000379:methods*; D014465:Ultrasonics
D012388:Root Canal Irrigants
Biofilm; fluid dynamics; irrigation; root canal; ultrasonic