title: Comparison of canal transportation and changes in canal curvature of two nickel-titanium rotary instruments.
abstract: BACKGROUND
  The aim of this study was to compare the canal transportation and changes in canal curvature after canal preparation with 2 nickel-titanium (NiTi) rotary instruments, Twisted (TF) and K3 file systems.
  
  
  METHODS
  Forty mandibular molar canals with angles of curvature between 25 and 35 degrees were randomly divided into 2 groups. Canals in K3 group were instrumented by using K3 rotary system. Canals in TF group were instrumented by using TF rotary system. All canals were instrumented with crown-down methodology to working length at a speed of 350 rpm and a torque-control level of 3 by using an 8:1 reduction handpiece. The final apical preparation was set to #30 in both groups. By using a radiographic platform, reproducible preinstrumentation and postinstrumentation radiographs were taken. The difference between the preinstrumentation and postinstrumentation angles was calculated and statistically analyzed by using unpaired t test.
  
  
  RESULTS
  TF recorded statistically significant lower percentage of change in canal curvature (-2.99%) than K3 group (P < .05).
  
  
  CONCLUSIONS
  TF system produced significantly less transportation and preserved the original canal to a greater degree than did the K3 system.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Ain Shams University, Cairo, Egypt. kbatouty@hotmail.com
authors.forename: Kariem M
authors.initials: KM
authors.lastname: El Batouty
authors.forename: Waleed E
authors.initials: WE
authors.lastname: Elmallah
mesh_terms: D003722:Dental Alloys; D003762:Dental Instruments / Q000009:adverse effects*; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000293:injuries; D003804:Dentin / Q000293:injuries*; D004867:Equipment Design; D006801:Humans; D008963:Molar; D009532:Nickel; D011859:Radiography; D018915:Root Canal Preparation / Q000009:adverse effects* / Q000295:instrumentation* / Q000379:methods; D014025:Titanium; D054159:Torsion, Mechanical
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium