title: Incidence of root face alteration after ultrasonic retrograde cavity preparation.
abstract: OBJECTIVE
  Ultrasonic root end preparation is now a recognized clinical procedure. Advantages claimed include improved access to the surgical site (because of reduced root end bevel), and faster more conservative preparation of the root end cavity. However, cracking of the root face has been reported after preparation.
  
  
  OBJECTIVE
  The aim of this study was to determine the incidence of root end cracking at varying ultrasonic power levels with a replica technique and scanning electron microscopy.
  
  
  METHODS
  The root canals of 55 single-rooted teeth were prepared to size 40 apically and obturated with laterally condensed gutta perch and sealer. Root ends were resected at 90 degrees 3 mm from the apex. Class 1 cavities (n = 5) were prepared with retro tips in a Neosonic handpiece with different power settings. Time of preparation and load applied were constant. Another experimental group (n = 5) was prepared with a no. 1 rotary bur. A replica technique with addition-cured silicone impression material and epoxy resin was used to prevent drying artefacts. Specimens were viewed under scanning electron microscope for alterations of the root face.
  
  
  RESULTS
  Results showed no root face cracking across the full range of instrument power settings, although chipping of the retrograde cavity margins was observed. No cracking was noted in bur-prepared teeth.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, University of Birmingham, U.K.
authors.forename: M
authors.initials: M
authors.lastname: Waplington
authors.forename: P J
authors.initials: PJ
authors.lastname: Lumley
authors.forename: A D
authors.initials: AD
authors.lastname: Walmsley
mesh_terms: D000704:Analysis of Variance; D006801:Humans; D008855:Microscopy, Electron, Scanning; D016628:Replica Techniques; D012184:Retrograde Obturation; D018915:Root Canal Preparation / Q000009:adverse effects* / Q000295:instrumentation; D018709:Statistics, Nonparametric; D013499:Surface Properties; D014082:Tooth Fractures / Q000209:etiology*; D014092:Tooth Root / Q000293:injuries* / Q000648:ultrastructure; D014464:Ultrasonic Therapy / Q000009:adverse effects