title: Effect of root canal dimensions, injection rate, and needle design on the apical extrusion of an irrigant: an in vitro study.
abstract: OBJECTIVE
  The purpose of this study was to determine the effect of root canal dimensions, type of needle, and injection rate on the apical extrusion of an irrigant in a simulated root canal.
  
  
  METHODS
  Ten students used two types of 28-gauge needles, to deliver 3 mL irrigant solution into artificial canals prepared in acrylic blocks to a standard size of ISO 25, 30, or 40 (0.06 taper; n = 10). Each block was preweighed to the nearest microgram before and after irrigation once the canal was dried with paper points. This was repeated with a syringe pump at a flow rate of 50, 100, 200 or 300 μL/s with the needle inserted to a standard depth.
  
  
  RESULTS
  Significant differences were observed between the side-vented and notched-end needles when the rate of irrigation was higher than 100 μL/s, and when the apical size was below ISO 40 (P < 0.001). The amount of extrusion was more variable and significantly higher when irrigation was performed manually, compared with the syringe pump groups.
  
  
  CONCLUSIONS
  Injection rates above 100 μL/s increased the risk of extrusion, whereas increasing the apical canal size to ISO 40 reduced the amount of extrusion in all groups. The use of a side-vented needle negates the injection-rate effects.
authors.affiliation: Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
authors.forename: Jeffrey W W
authors.initials: JW
authors.lastname: Chang
authors.affiliation: Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
authors.forename: Amelia W T
authors.initials: AW
authors.lastname: Cheung
authors.affiliation: Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
authors.forename: Gary S P
authors.initials: GS
authors.lastname: Cheung
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D004867:Equipment Design; D005119:Extravasation of Diagnostic and Therapeutic Materials / Q000209:etiology*; D006801:Humans; D066298:In Vitro Techniques; D007267:Injections / Q000295:instrumentation; D008953:Models, Anatomic; D009339:Needles; D011312:Pressure; D012212:Rheology; D012388:Root Canal Irrigants / Q000008:administration & dosage*; D013594:Syringes; D007507:Therapeutic Irrigation / Q000295:instrumentation*; D019227:Tooth Apex / Q000033:anatomy & histology*
chemical_list: D012388:Root Canal Irrigants
keywords: apical extrusion; injection rate; irrigant; need design; root canal injection