title: Ultrasonic root end cavity preparation assessed by an in situ impression technique.
abstract: OBJECTIVE
  In vitro studies have demonstrated microfractures in resected roots after root end cavity preparation with ultrasonic tips. Such microfractures are of concern; however, they may be artifacts.
  
  
  OBJECTIVE
  To assess the incidence of microfractures after ultrasonic root end cavity preparation in situ.
  
  
  METHODS
  Fifty-two roots in two cadavers were endodontically treated, the soft tissues excised, and the root ends exposed and resected. The resected root surfaces were replicated with polyvinylsiloxane impressions. Root end cavities were prepared with ultrasonic tips, then impressed a second time. The roots were retrieved; 25 were processed for direct SEM examination as were both the impressions of each root. The specimens were examined by stereomicroscope and scanning electron microscope.
  
  
  RESULTS
  In the impressions, the resected and prepared surfaces appeared irregular, but none demonstrated microfractures. In contrast, 15 retrieved roots showed microfractures.
  
  
  CONCLUSIONS
  Ultrasonic root end cavity preparation in situ did not cause root microfractures, and the impression technique could be clinically usable with minor modifications.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, University of Toronto, Ontario, Canada.
authors.forename: K J
authors.initials: KJ
authors.lastname: Calzonetti
authors.forename: T
authors.initials: T
authors.lastname: Iwanowski
authors.forename: R
authors.initials: R
authors.lastname: Komorowski
authors.forename: S
authors.initials: S
authors.lastname: Friedman
mesh_terms: D016477:Artifacts; D003761:Dental Impression Technique; D003804:Dentin / Q000648:ultrastructure; D006801:Humans; D008855:Microscopy, Electron, Scanning; D018915:Root Canal Preparation / Q000009:adverse effects / Q000295:instrumentation*; D018709:Statistics, Nonparametric; D014082:Tooth Fractures / Q000209:etiology*; D014092:Tooth Root / Q000293:injuries* / Q000648:ultrastructure; D014464:Ultrasonic Therapy / Q000009:adverse effects