title: Probability of removing fractured instruments from root canals.
abstract: OBJECTIVE
  To evaluate in a clinical case series the location of fractured instruments, how many of them could be removed and to compare these findings with the results of a similar study.
  
  
  METHODS
  Within an 18-month period all referred endodontic cases involving fractured instruments within root canals were analysed. The protocol for removal of fractured instruments was: create straight-line access to the coronal portion of the fractured instrument, attempt to create a ditched groove around the coronal aspect of the instrument using ultrasonic files and/or to bypass it with K-Files. Subsequently, the fractured instrument was vibrated ultrasonically and flushed out of the root canal or an attempt was made to remove the instrument with the Tube-and-Hedström file-Method or similar techniques. The location of the fractured instrument and the time required for removal were recorded. Successful removal was defined as complete removal from the root canal without creating a clinically detectable perforation.
  
  
  RESULTS
  In total, 97 consecutive cases of instrument fracture were included in the time period. In all, 84 instruments (87%) were removed successfully. There was a significant correlation between the time needed to remove fractured instruments and a decrease in success rate. Curved canals had significantly more fractured instruments than straight canals (P < 0.05). Rotary instruments fractured significantly more often in curved canals (P < 0.05) compared with other instruments. Half of all instrument fractures occurred in mesial roots of lower molars and most often when using rotating instruments. There was no statistically significant difference in the success rate with respect to the location of the fractured instrument (tooth/root type), the type of fractured instrument or the different methods of instrument removal.
  
  
  CONCLUSIONS
  Curved canals are a higher risk for instrument fracture than straight canals. In curved canals rotary instruments (including lentulo spirals) fractured more often than other instruments. In all, 87% of the fractured instruments were removed successfully. A decrease in success rate was evident with increasing treatment time. The use of an operating microscope was a prerequisite for the techniques used to remove the fractured instruments.
authors.affiliation: Private Endodontic Practice, Berne, Switzerland. bs@endodontics-bern.ch
authors.forename: B
authors.initials: B
authors.lastname: Suter
authors.forename: A
authors.initials: A
authors.lastname: Lussi
authors.forename: P
authors.initials: P
authors.lastname: Sequeira
mesh_terms: D016009:Chi-Square Distribution; D003762:Dental Instruments / Q000009:adverse effects* / Q000706:statistics & numerical data; D003786:Dental Pulp Cavity; D019232:Dental Restoration Failure; D004868:Equipment Failure / Q000706:statistics & numerical data; D005547:Foreign Bodies / Q000209:etiology / Q000628:therapy*; D006801:Humans; D008853:Microscopy / Q000295:instrumentation; D011336:Probability; D019233:Retreatment; D018915:Root Canal Preparation / Q000295:instrumentation*; D014464:Ultrasonic Therapy