title: Effect of the precrack preparation with an ultrasonic instrument on the ceramic bracket removal.
abstract: OBJECTIVE
  In terms of fracture mechanics, a precrack preparation may facilitate the propagation of a break through the expected fracture plane during the bracket debonding process. The purpose of this study was to evaluate the effect of an ultrasonic precrack preparation on the debonding force and failure modes of ceramic bracket removal.
  
  
  METHODS
  Eighty extracted premolars were assigned to four groups: Inspire, precrack Inspire, Clarity, and precrack Clarity groups, with each group containing 20 teeth. The precrack preparations were made at the mesial gingival line angle of Inspire brackets and on the mesial side of Clarity brackets with an ultrasonic tip. Debonding force, failure modes, and bracket breakage score were measured and recorded. Fracture surfaces after bracket debonding were observed with scanning electron microscopy (SEM).
  
  
  RESULTS
  We found that the ultrasonic precrack preparation could significantly decrease the average debonding force and the mean bracket breakage scores of both kinds of ceramic brackets. After bracket debonding, 80% of brackets in the precrack Inspire group and 100% of brackets in the precrack Clarity group showed no bracket failure. However, only 25% of brackets in the Inspire group and 75% of brackets in the Clarity group showed no bracket failure. SEM micrographs showed a precrack notch at the adhesive resin after precrack preparation, and no enamel damage was noted after the bracket debonding.
  
  
  CONCLUSIONS
  The ultrasonic precrack preparation can significantly decrease the debonding force and may guide the bracket debonding through a favorable fracture plane without damage to either the bracket or the enamel.
authors.affiliation: Graduate Institute of Clinical Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan.
authors.forename: Yen-Liang
authors.initials: YL
authors.lastname: Chen
authors.affiliation: Graduate Institute of Clinical Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan.
authors.forename: Hsing-Yu
authors.initials: HY
authors.lastname: Chen
authors.affiliation: Graduate Institute of Clinical Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan.
authors.forename: Yu-Chih
authors.initials: YC
authors.lastname: Chiang
authors.affiliation: Graduate Institute of Clinical Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan.
authors.forename: Hao-Hueng
authors.initials: HH
authors.lastname: Chang
authors.affiliation: Graduate Institute of Clinical Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan. Electronic address: pinlin@ntu.edu.tw.
authors.forename: Chun-Pin
authors.initials: CP
authors.lastname: Lin
mesh_terms: D001641:Bicuspid / Q000000981:diagnostic imaging*; D002516:Ceramics; D017005:Dental Debonding / Q000295:instrumentation*; D003743:Dental Enamel; D003799:Dental Stress Analysis; D004868:Equipment Failure; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016910:Orthodontic Brackets; D014464:Ultrasonic Therapy / Q000379:methods*
keywords: bracket breakage score; ceramic bracket; debonding force; failure mode; precrack preparation; ultrasonic tip