title: Fracture strength of mesiobuccal roots following canal preparation with hand and rotary instrumentation: an in vitro study.
abstract: BACKGROUND
  The aim of this in vitro study was to compare the effect of hand and rotary instruments on fracture strength of tooth roots.
  
  
  METHODS
  Thirty two teeth were randomly divided into two experimental groups of 15 each and one negative control group with two samples. In group 1, step-back technique with conventional stainless steel K-files was used, and in group 2, instrumentation was performed using rotary Ni-Ti Hero642. Samples in control group did not receive cleaning or shaping after access cavity preparation. After obturating each canal, tip of the spreader was locked within canal. The required force for root fracture was measured using Instron testing machine. Recorded data was statistically analyzed using t-test.
  
  
  RESULTS
  The mean and standard deviation force required for vertical root fracture were 50.33±19.1 and 63.1±25.46 N for hand and rotary groups respectively. However, no significant difference was found between experimental groups.
  
  
  CONCLUSIONS
  The results indicate that the manual technique did not lower fracture strength of obturated roots in comparison with the rotary preparation technique.
authors.affiliation: Department of Endodontics, Dental School, Islamic Azad University of Medical Sciences, Khorasgan, Isfahan, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Zare Jahromi
authors.forename: Parvin
authors.initials: P
authors.lastname: Mirzakouchaki
authors.forename: Elnaz
authors.initials: E
authors.lastname: Mousavi
authors.forename: Amir Arsalan
authors.initials: AA
authors.lastname: Navabi
keywords: Dental Equipment; Endodontics; Root Canal Preparation; Root Fracture; Tooth Fracture