title: Success rates for removing or bypassing fractured instruments: a prospective clinical study.
abstract: BACKGROUND
  The objective of this study was to evaluate the success rates of standardized techniques for removing or bypassing fractured instruments from root canals and determine whether visualization of the fractured instrument with the aid of an operating microscope has any impact on the success rates.
  
  
  METHODS
  In this prospective study, attempts were made to visualize 112 fractured instruments under a dental operating microscope after creating a straight-line access to the fragment. By using ultrasonic tips alone or associated with bypassing, the Ruddle technique was attempted to remove the 68 visible instruments. Bypassing was performed for the 44 nonvisible fragments. The χ(2) test was performed to assess whether any significant difference occurred between the success rates observed for the visible and nonvisible fractured instrument groups.
  
  
  RESULTS
  The overall success rate (removal and bypassing) was 70.5% (n = 79). In the visible fragment group, the success rate was 85.3% (n = 58), and in the nonvisible fragment group it was 47.7% (n = 21). Success rates were significantly higher when the fragment was visible (P = .0009).
  
  
  CONCLUSIONS
  The standardized techniques used in this study for removing or bypassing fractured instruments were effective, and approximately 2 times greater success rate was obtained when the fragment was visible inside the root canal compared with when it was nonvisible.
authors.affiliation: Graduate Program in Endodontics, São Leopoldo Mandic Dental Research Center, Campinas, São Paulo, Brazil. gnevares@yahoo.com
authors.forename: Giselle
authors.initials: G
authors.lastname: Nevares
authors.forename: Rodrigo Sanches
authors.initials: RS
authors.lastname: Cunha
authors.forename: Mário Luis
authors.initials: ML
authors.lastname: Zuolo
authors.forename: Carlos Eduardo da Silveira
authors.initials: CE
authors.lastname: Bueno
mesh_terms: D001641:Bicuspid / Q000473:pathology; D003481:Cuspid / Q000473:pathology; D003764:Dental Materials / Q000737:chemistry; D003786:Dental Pulp Cavity / Q000473:pathology; D004867:Equipment Design; D004868:Equipment Failure; D005547:Foreign Bodies / Q000145:classification / Q000628:therapy*; D006801:Humans; D007180:Incisor / Q000473:pathology; D008866:Microsurgery / Q000295:instrumentation; D008963:Molar / Q000473:pathology; D059745:Piezosurgery / Q000295:instrumentation; D011446:Prospective Studies; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000009:adverse effects / Q000295:instrumentation*; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D014025:Titanium / Q000737:chemistry; D016896:Treatment Outcome; D015040:Zirconium / Q000737:chemistry
chemical_list: D003764:Dental Materials; D012388:Root Canal Irrigants; D015040:Zirconium; D014025:Titanium; D012973:Sodium Hypochlorite