title: Uncontrolled Removal of Dentin during In Vitro Ultrasonic Irrigant Activation.
abstract: BACKGROUND
  The aim of this study was to evaluate uncontrolled removal of dentin during in vitro ultrasonic irrigant activation in prepared root canals using 2 different files.
  
  
  METHODS
  Fifty-four human single-rooted teeth with straight root canals were prepared to size 35/.06 taper. The specimens were randomly allocated to 3 groups (n = 18). Two milliliters of 2% sodium hypochlorite was delivered 3 times to each root canal by a syringe and an open-ended needle. After each delivery, the irrigant was ultrasonically activated for 10 seconds at 35% power either by a size 15 ultrasonic K-file (group A) or a size 20 Irrisafe file (Acteon Satelec, Merignac, France) (group B) placed at 2 mm short of the working length. The irrigant in the control specimens (group C) was not activated. Specimens were scanned by micro-computed tomographic imaging at 10-μm voxel size before preparation, after preparation, and after the final irrigation/activation sequence. Scans were coregistered and segmented, and the amount of dentin removed during the final step was quantified by morphologic operations. Results were analyzed by nonparametric statistical tests. The level of significance was set to P < .05.
  
  
  RESULTS
  Defects with a maximum depth of 0.09 mm and 0.07 mm were identified in groups A and B, respectively. Both ultrasonic files removed significantly more dentin than irrigant delivery in the control group (P ≤ .005). K-files removed significantly more dentin than Irrisafe files in the apical third (P = .001).
  
  
  CONCLUSIONS
  Ultrasonic irrigant activation may result in uncontrolled removal of dentin in straight root canals and at manufacturer-recommended power settings.
authors.affiliation: Department of Endodontology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands. Electronic address: c.boutsioukis@acta.nl.
authors.forename: Christos
authors.initials: C
authors.lastname: Boutsioukis
authors.affiliation: Department of Endodontology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands.
authors.forename: Nestor
authors.initials: N
authors.lastname: Tzimpoulas
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D003804:Dentin / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods; D011897:Random Allocation; D012388:Root Canal Irrigants / Q000009:adverse effects*; D018915:Root Canal Preparation / Q000009:adverse effects* / Q000379:methods; D007507:Therapeutic Irrigation / Q000009:adverse effects / Q000379:methods; D019227:Tooth Apex / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D014092:Tooth Root / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000473:pathology; D014464:Ultrasonic Therapy / Q000009:adverse effects* / Q000379:methods; D014465:Ultrasonics / Q000295:instrumentation / Q000379:methods*; D014732:Vibration
chemical_list: D012388:Root Canal Irrigants
keywords: Dentin; Irrisafe; K-file; micro–computed tomography; removal; ultrasonic activation