title: Irrigant flow beyond the insertion depth of an ultrasonically oscillating file in straight and curved root canals: visualization and cleaning efficacy.
abstract: BACKGROUND
  The purpose of this study was to evaluate the influence of the insertion depth of an ultrasonically oscillating file on the ability to remove dentin debris from simulated canal irregularities in an extracted tooth model of a straight root canal and its influence on the flow of irrigant in both straight and curved canals.
  
  
  METHODS
  A tooth model with artificial depressions in 1 canal wall at 0.5, 2, 4, and 6 mm from the working length was used. Ultrasonic-activated irrigation was performed with the file inserted 1, 2, 3, 4, or 5 mm short of the working length. Dye penetration and high-speed recordings of the flow in straight and curved canals showed the static and dynamic behavior of the flow during ultrasonic activation.
  
  
  RESULTS
  The overall cleaning efficacy decreased with increasing distance between the file and the apex, with the depressions next to the file and within 3 mm in front of the file being the cleanest. The flow observed from the visualization experiments matched this distance, suggesting a direct relation between flow and cleaning. The observed flow depth increased with increasing power setting; the curvature of the root canal had no influence on the flow depth. High-speed imaging showed a start-up phase with deeper fluid activation than in the steady phase afterward.
  
  
  CONCLUSIONS
  The ultrasonically oscillating file could remove dentin debris up to 3 mm in front of the file tip, coinciding with the extent of the observed flow. The root canal curvature had no influence on the irrigant flow.
authors.affiliation: Department of Endodontics, Saint-Joseph University, Beirut, Lebanon.
authors.forename: Maher
authors.initials: M
authors.lastname: Malki
authors.forename: Bram
authors.initials: B
authors.lastname: Verhaagen
authors.forename: Lei-Meng
authors.initials: LM
authors.lastname: Jiang
authors.forename: Walid
authors.initials: W
authors.lastname: Nehme
authors.forename: Alfred
authors.initials: A
authors.lastname: Naaman
authors.forename: Michel
authors.initials: M
authors.lastname: Versluis
authors.forename: Paul
authors.initials: P
authors.lastname: Wesselink
authors.forename: Lucas
authors.initials: L
authors.lastname: van der Sluis
mesh_terms: D004396:Coloring Agents; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D003804:Dentin / Q000033:anatomy & histology; D006801:Humans; D057446:Hydrodynamics; D008422:Materials Testing; D010781:Photography; D012388:Root Canal Irrigants / Q000008:administration & dosage*; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D016369:Smear Layer; D013010:Sonication / Q000379:methods; D007507:Therapeutic Irrigation / Q000295:instrumentation / Q000379:methods; D019227:Tooth Apex / Q000033:anatomy & histology; D016896:Treatment Outcome; D014465:Ultrasonics / Q000295:instrumentation
chemical_list: D004396:Coloring Agents; D012388:Root Canal Irrigants