title: Necrotic pulp tissue dissolution by passive ultrasonic irrigation in simulated accessory canals: impact of canal location and angulation.
abstract: OBJECTIVE
  To evaluate whether passive ultrasonic irrigation (PUI) of 2.5% NaOCl would dissolve necrotic pulp tissue from simulated accessory root canals (SACs) better than passive placement of the irrigant, when temperature was equilibrated between the two treatments.
  
  
  METHODS
  Transparent root canal models (n = 6) were made from epoxy resin. SACs of 0.2 mm diameter were placed at defined angles and positions in the mid-canal and apical area. SACs were filled with necrotic bovine pulp tissue. PUI was performed five times for 1 min each with irrigant replenishment after every minute. Main canal temperature was measured after each minute, and a digital photograph was taken. In control experiments, mock treatments were performed with the same set-up without activation of the file using heated NaOCl to mimic the temperature created by PUI. Experiments were repeated five times. Digital photographs were analysed for the distance of dissolved tissue into the SACs in mm. Overall comparison (sum of dissolved tissue from all five accessory canals) between treatments was performed using paired t-test. Differences between SAC angulation and position after PUI were investigated using anova/Bonferroni (alpha < 0.05).
  
  
  RESULTS
  Passive ultrasonic irrigation caused a rise in irrigant temperature in the main canal to 53.5 +/- 2.7 degrees C after the fifth minute. PUI dissolved a total of 6.4 +/- 2.1 mm, mock treatment controlled for heat: 1.4 +/- 0.6 mm (P < 0.05). No significant influence of SAC position or angulation was found.
  
  
  CONCLUSIONS
  Passive ultrasonic irrigation promotes positive tissue-dissolving effects beyond a rise in irrigant temperature.
authors.affiliation: Department of Preventive Dentistry, Periodontology and Cariology, University of Zürich Center of Dental Medicine, Zürich, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Al-Jadaa
authors.forename: F
authors.initials: F
authors.lastname: Paqué
authors.forename: T
authors.initials: T
authors.lastname: Attin
authors.forename: M
authors.initials: M
authors.lastname: Zehnder
mesh_terms: D000818:Animals; D002417:Cattle; D003786:Dental Pulp Cavity / Q000187:drug effects* / Q000473:pathology; D003790:Dental Pulp Necrosis / Q000628:therapy*; D004853:Epoxy Resins; D006358:Hot Temperature; D007091:Image Processing, Computer-Assisted; D008422:Materials Testing; D008953:Models, Anatomic; D023861:Photography, Dental; D012388:Root Canal Irrigants / Q000008:administration & dosage / Q000627:therapeutic use*; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods; D012973:Sodium Hypochlorite / Q000008:administration & dosage / Q000627:therapeutic use; D012995:Solubility; D013696:Temperature; D013997:Time Factors; D019227:Tooth Apex / Q000187:drug effects / Q000473:pathology; D014464:Ultrasonic Therapy / Q000295:instrumentation / Q000379:methods*
chemical_list: D004853:Epoxy Resins; D012388:Root Canal Irrigants; D012973:Sodium Hypochlorite