title: In vitro particle image velocity measurements in a model root canal: flow around a polymer rotary finishing file.
abstract: BACKGROUND
  Root canal irrigation is vital to thorough debridement and disinfection, but the mechanisms that contribute to its effectiveness are complex and uncertain. Traditionally, studies in this area have relied on before-and-after static comparisons to assess effectiveness, but new in situ tools are being developed to provide real-time assessments of irrigation. The aim in this work was to measure a cross section of the velocity field in the fluid flow around a polymer rotary finishing file in a model root canal.
  
  
  METHODS
  Fluorescent microparticles were seeded into an optically accessible acrylic root canal model. A polymer rotary finishing file was activated in a static position. After laser excitation, fluorescence from the microparticles was imaged onto a frame-transfer camera. Two consecutive images were cross-correlated to provide a measurement of a projected, 2-dimensional velocity field.
  
  
  RESULTS
  The method reveals that fluid velocities can be much higher than the velocity of the file because of the shape of the file. Furthermore, these high velocities are in the axial direction of the canal rather than only in the direct of motion of the file.
  
  
  CONCLUSIONS
  Particle image velocimetry indicates that fluid velocities induced by the rotating file can be much larger than the speed of the file. Particle image velocimetry can provide qualitative insight and quantitative measurements that may be useful for validating computational fluid dynamic models and connecting clinical observations to physical explanations in dental research.
authors.affiliation: Marquette University College of Engineering, Milwaukee, Wisconsin. Electronic address: jondkoch@gmail.com.
authors.forename: Jon D
authors.initials: JD
authors.lastname: Koch
authors.affiliation: Marquette University College of Engineering, Milwaukee, Wisconsin.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Smith
authors.affiliation: Marquette University College of Engineering, Milwaukee, Wisconsin.
authors.forename: Daniel
authors.initials: D
authors.lastname: Garces
authors.affiliation: Marquette University College of Engineering, Milwaukee, Wisconsin.
authors.forename: Luyang
authors.initials: L
authors.lastname: Gao
authors.affiliation: Marquette University School of Dentistry, Milwaukee, Wisconsin.
authors.forename: F Kris
authors.initials: FK
authors.lastname: Olsen
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D004867:Equipment Design; D005456:Fluorescent Dyes; D006801:Humans; D057446:Hydrodynamics; D053844:Lasers, Solid-State; D008953:Models, Anatomic; D061848:Optical Imaging / Q000379:methods; D010781:Photography / Q000379:methods; D011108:Polymers / Q000737:chemistry; D012212:Rheology / Q000379:methods; D012388:Root Canal Irrigants / Q000737:chemistry*; D012399:Rotation; D013499:Surface Properties; D007507:Therapeutic Irrigation / Q000295:instrumentation*
chemical_list: D000180:Acrylic Resins; D005456:Fluorescent Dyes; D011108:Polymers; D012388:Root Canal Irrigants
keywords: Flow visualization; PIV; polymer rotary finishing file; velocimetry