title: Visualization of removal of trapped air from the apical region of the straight root canal models generating 2-phase intermittent counter flow during ultrasonically activated irrigation.
abstract: BACKGROUND
  The purpose of this in vitro study was to obtain a better understanding of the mechanism of irrigant traveling apically and generating 2-phase intermittent counter flow in straight root canal models during activation of the irrigant by ultrasonic means in an endodontic procedure.
  
  
  METHODS
  A high-speed imaging system, with high temporal and spatial resolution (FastCam SA5; Photron, Tokyo, Japan) at a frame rate of 100,000 frames per second using a macro lens (60 mm, f/2.8; Nikon, Tokyo, Japan), was used to visualize, in glass models of root canals, an ultrasonically induced acoustic pressure wave in an EDTA solution environment. A 25-mm stainless steel noncutting file #20 driven by an ultrasonic device (P5 Newtron; Satelec Acteon, Mérignac, France) at power settings of 5 and 7 produced disturbances at the solution-air interface.
  
  
  RESULTS
  We found that apically directed travel of the irrigant was caused by disruption of the surface tension at the solution-air interface. This disruption caused by ultrasonic activation energy displaced air in the form of bubbles from the apical region toward the solution.
  
  
  CONCLUSIONS
  The apical movement of the solution may be attributed to ultrasonically induced wave generation at the solution-air interface, resulting in the removal of trapped air from the root canal and allowing the solution to travel apically in the opposite directions (via a 2-phase intermittent counter flow).
authors.affiliation: Laser Research Center, Bandung, Indonesia. Electronic address: h2huiz@cbn.net.id.
authors.forename: Harry Huiz
authors.initials: HH
authors.lastname: Peeters
authors.affiliation: Department of Conservative Dentistry, Faculty of Dentistry, Universitas Trisakti, Jakarta, Indonesia.
authors.forename: Bernard
authors.initials: B
authors.lastname: Iskandar
authors.affiliation: Department of Conservative Dentistry, Faculty of Dentistry, Universitas Airlangga, Surabaya, Indonesia.
authors.forename: Ketut
authors.initials: K
authors.lastname: Suardita
authors.affiliation: Faculty of Mechanical and Aerospace Engineering, Institut Teknologi Bandung, Bandung, Indonesia.
authors.forename: Djoko
authors.initials: D
authors.lastname: Suharto
mesh_terms: D000388:Air; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D004492:Edetic Acid / Q000737:chemistry / Q000528:radiation effects; D006801:Humans; D057446:Hydrodynamics; D007091:Image Processing, Computer-Assisted / Q000379:methods; D045423:Microbubbles; D008953:Models, Anatomic; D010781:Photography / Q000379:methods; D011312:Pressure; D012212:Rheology; D012388:Root Canal Irrigants / Q000737:chemistry / Q000528:radiation effects*; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods; D013500:Surface Tension; D019227:Tooth Apex / Q000033:anatomy & histology*; D000069453:Ultrasonic Waves
chemical_list: D012388:Root Canal Irrigants; D004492:Edetic Acid
keywords: 2-Phase intermittent counter flow; acoustic pressure wave; endodontics; solution-air interface; surface tension; ultrasonic