title: Computed tomographic evaluation of canal shape instrumented by different kinematics rotary nickel-titanium systems.
abstract: BACKGROUND
  This study evaluated the effects of 2 different kinematics rotary nickel-titanium (NiTi) systems, Twisted File (TF), a continuous rotation full-sequence system, and WaveOne (WO), a reciprocating single-file system, on transportation, curvature, and volumetric changes of curved root canals by using cone-beam computed tomography.
  
  
  METHODS
  Forty mesiobuccal canals of mandibular molars with angle of curvature ranging from 25°-35° were divided according to the NiTi rotary system used in canal preparation into 2 groups of 20 samples each, TF group and WO group. Canals were scanned by using an i-CAT cone-beam computed tomography scanner before and after instrumentation to evaluate canal transportation at coronal, middle, and apical thirds, canal curvature, and volumetric changes. The significance level was set at P ≤ .05.
  
  
  RESULTS
  TF system recorded significantly lower mean of canal transportation than WO group at all canal thirds (apical P = .034, middle P = .003, and coronal P = .012). In both groups the apical third recorded the significantly least amount of transportation (P < .05). There was no significant difference between the 2 groups in canal curvature and volumetric changes after instrumentation (P > .05).
  
  
  CONCLUSIONS
  Both TF and WO NiTi systems can be safely used to the full working length, resulting in satisfactory preservation of the original canal shape.
authors.affiliation: Department of Endodontics, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt.
authors.forename: Abeer M
authors.initials: AM
authors.lastname: Marzouk
authors.forename: Angie G
authors.initials: AG
authors.lastname: Ghoneim
mesh_terms: D019412:Anatomy, Cross-Sectional; D003722:Dental Alloys / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008963:Molar / Q000000981:diagnostic imaging; D009532:Nickel / Q000737:chemistry*; D009811:Odontometry / Q000379:methods; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D014025:Titanium / Q000737:chemistry*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D019227:Tooth Apex / Q000000981:diagnostic imaging
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium