title: [Computational fluid dynamics analysis of the flow of four irrigations in root canal].
abstract: OBJECTIVE
  To analyze the flow of four irrigations in a root canal with different needle-insertion depth by using a computational fluid dynamics (CFD) model in order to provide a reference to the needle placement in clinical practice.
  
  
  METHODS
  The density and viscosity of 5.25% sodium hypochlorite (A), 3% sodium hypochlorite (B), 17% ethylenediaminetetraacetic acid (EDTA, C), 2% chlorhexidine (D) were measured. A CFD model by ICEM software was used to simulate irrigant flow from an open-ended flat needle positioned at the depth of 1, 3, 5 mm to the physiological apical within the root canal. Velocity, wall shear stress and pressure in the root canal were evaluated after setting the computing conditions with FLUENT14.0 software.
  
  
  RESULTS
  All the wall shear stress generated by four fluids was at peak when the needle was positioned 1 mm to the physiological apical, which were 6.72 × 10³ Pa(A), 6.35 × 10³ Pa(B), 7.47 × 10³ Pa(C), 5.26 × 10³ Pa(D), respectively. With the distance increasing, wall shear stress gradually decreased. The wall shear stress of A, B, C, D was 2.31 × 10³, 2.05 × 10³, 2.59 × 10³ and 1.81 × 10³ Pa, respectively in 3 mm group. The wall shear stress of A, B, C, D was 2.16 × 10³, 1.91 × 10³, 2.42 × 10³, 1.71 × 10³ Pa, respectively in 5 mm group.
  
  
  CONCLUSIONS
  It was recommended that the distance between the needle and physiological apical is 1-3 mm when flushing the root canal. The injection speed of 17% EDTA should be slower than that of the other three solutions.
authors.affiliation: Department of Stomatology, The Fourth Hospital of Harbin Medical University, Harbin 150001, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Department of Stomatology, The Fourth Hospital of Harbin Medical University, Harbin 150001, China.
authors.forename: Jialong
authors.initials: J
authors.lastname: Han
authors.affiliation: Department of Stomatology, The Fourth Hospital of Harbin Medical University, Harbin 150001, China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Yu
authors.affiliation: Department of Stomatology, The Fourth Hospital of Harbin Medical University, Harbin 150001, China; Email: 798879842@qq.com.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Wang
mesh_terms: D002710:Chlorhexidine / Q000008:administration & dosage*; D003786:Dental Pulp Cavity; D004492:Edetic Acid / Q000008:administration & dosage*; D006801:Humans; D057446:Hydrodynamics; D009339:Needles; D012212:Rheology; D012388:Root Canal Irrigants / Q000008:administration & dosage*; D018915:Root Canal Preparation; D012390:Root Canal Therapy / Q000295:instrumentation; D012973:Sodium Hypochlorite / Q000008:administration & dosage*; D012984:Software
chemical_list: D012388:Root Canal Irrigants; D004492:Edetic Acid; D012973:Sodium Hypochlorite; D002710:Chlorhexidine