title: Factors associated with the removal of fractured NiTi instruments from root canal systems.
abstract: OBJECTIVE
  To evaluate the influence of various factors on the success or failure of attempts to remove fragments of separated NiTi instruments from root canals.
  
  
  METHODS
  Instrument removal attempts were undertaken on 72 teeth with a separated NiTi instrument using a variety of techniques and armamentarium. Factors including type of tooth, degree of root canal curvature, location of fragment in relation to the root canal curvature, and radiographic length of fragment were analyzed. A success of treatment was defined as removal or complete bypassing of the fragments.
  
  
  RESULTS
  The overall success rate was 53%. The success rate for ProFile fragments was 41% and for the NiTi K-file 60%. The success rate in maxillary teeth was higher than that in mandibular teeth. Of 52 instruments in molars, 28 were successfully removed or bypassed. Of the 12 fragments in premolars, only 2 were removed. All 8 cases in anterior teeth were retrieved completely. When the fragment was localized before the curvature, complete removal was achieved. When the fragments were located at and beyond the curvature, the success rates were 60% and 31%, respectively. In canals with a slight, moderate, and severe curvature, the success rates were 100%, 83%, and 43%, respectively. In general, the longer the fragment, the greater the chance for successful removal or bypass.
  
  
  CONCLUSIONS
  Favorable factors for removal of separated NiTi fragments are straight root canals, anterior teeth, localization before the curvature, fragments longer than 5 mm, and hand NiTi K-file.
authors.affiliation: Department of Operative Dentistry and Endodontics, School of Stomatology, Wuhan University, Wuhan, China.
authors.forename: Ya
authors.initials: Y
authors.lastname: Shen
authors.forename: Bin
authors.initials: B
authors.lastname: Peng
authors.forename: Gary Shun-Pan
authors.initials: GS
authors.lastname: Cheung
mesh_terms: D001641:Bicuspid / Q000473:pathology; D003481:Cuspid / Q000473:pathology; D003722:Dental Alloys; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging / Q000473:pathology; D004867:Equipment Design; D004868:Equipment Failure; D005547:Foreign Bodies / Q000473:pathology / Q000628:therapy*; D006801:Humans; D007180:Incisor / Q000473:pathology; D008334:Mandible; D008437:Maxilla; D008963:Molar / Q000473:pathology; D009532:Nickel; D011859:Radiography; D018915:Root Canal Preparation / Q000009:adverse effects / Q000295:instrumentation*; D013499:Surface Properties; D014025:Titanium; D016896:Treatment Outcome
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium