title: Microscopic computerized tomographic evaluation of root canal transportation prepared with twisted or ground nickel-titanium rotary instruments.
abstract: OBJECTIVE
  The aim of this study was to evaluate, ex vivo, canal transportation and the centering ability of nickel-titanium rotary instruments manufactured by twisting and by traditional grinding, with the use of microscopic computerized tomography (μCT).
  
  
  METHODS
  Fifteen mandibular molars were embedded in a rubber-based impression material and submitted to μCT before and after instrumentation. Images were reconstructed, and cross-sections corresponding to distances 1, 2, 3, 4, 5, 6, and 7 mm from the anatomic apex were selected for analysis. Statistical analysis was performed with Mann-Whitney test.
  
  
  RESULTS
  Canal transportation and centering ability results were similar for both instruments. Statistically significant differences (P < .05) were observed only at the 3 and 4 mm cross-sections, with lower levels of apical transportation and a better centering ratio associated with twisted instruments than with ground instruments.
  
  
  CONCLUSIONS
  Our findings showed that twisted and ground instruments behaved similarly, allowing the preparation of curved canals with little transportation, which occurred in both mesial and distal directions.
authors.affiliation: Discipline of Endodontics, Department of Esthetic Dentistry, School of Dentistry, University of São Paulo, São Paulo, Brazil. lailafreire@gmail.com
authors.forename: Laila Gonzales
authors.initials: LG
authors.lastname: Freire
authors.forename: Giulio
authors.initials: G
authors.lastname: Gavini
authors.forename: Fernando
authors.initials: F
authors.lastname: Branco-Barletta
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Sanches-Cunha
authors.forename: Marcelo
authors.initials: M
authors.lastname: dos Santos
mesh_terms: D019412:Anatomy, Cross-Sectional / Q000379:methods; D002614:Chelating Agents / Q000627:therapeutic use; D003722:Dental Alloys / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000648:ultrastructure*; D004492:Edetic Acid / Q000627:therapeutic use; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008963:Molar / Q000648:ultrastructure; D009532:Nickel / Q000737:chemistry*; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000592:standards; D012399:Rotation; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D019227:Tooth Apex / Q000648:ultrastructure; D055114:X-Ray Microtomography / Q000379:methods*
chemical_list: D002614:Chelating Agents; D003722:Dental Alloys; D012388:Root Canal Irrigants; C040654:titanium nickelide; D009532:Nickel; D004492:Edetic Acid; D014025:Titanium; D012973:Sodium Hypochlorite