title: Effect of nitrogen ion implantation on the flexibility of rotary nickel-titanium instruments.
abstract: BACKGROUND
  The aim of this study was to assess the effect of nitrogen ion implantation on the flexibility of rotary nickel-titanium (NiTi) instruments as measured by the load required to bend implanted and nonimplanted instruments at a 30° angle.
  
  
  METHODS
  Thirty K3 files, size #40, 0.02 taper and 25-mm length, were allocated into 2 groups as follows: group A, 15 files exposed to nitrogen ion implantation at a dose of 2.5 × 10(17) ions/cm(2), voltage 200 KeV, current density 1 μA/cm(2), temperature 130°C, and vacuum conditions of 10 × 10(-6) mm Hg for 6 hours; and group B, 15 nonimplanted files. One extra file was used for process control. All instruments were subjected to bend testing on a modified troptometer, with measurement of the load required for flexure to an angle of 30°. The Mann-Whitney U test was used for statistical analysis. Findings with P <.05 were considered significant.
  
  
  RESULTS
  The mean load required to bend instruments at a 30° angle was 376.26 g for implanted instruments and 383.78 g for nonimplanted instruments. The difference was not statistically significant.
  
  
  CONCLUSIONS
  Our findings show that nitrogen ion implantation has no appreciable effect on the flexibility of NiTi instruments.
authors.affiliation: Discipline of Endodontics, Department of Esthetic Dentistry, School of Dentistry, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: Marcelo
authors.initials: M
authors.lastname: dos Santos
authors.forename: Giulio
authors.initials: G
authors.lastname: Gavini
authors.forename: Evandro Luiz
authors.initials: EL
authors.lastname: Siqueira
authors.forename: Cristiane
authors.initials: C
authors.lastname: da Costa
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D055664:Electrochemical Techniques / Q000379:methods*; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing; D008669:Metallurgy / Q000379:methods; D009532:Nickel / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*; D014618:Vacuum
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium; D009584:Nitrogen