title: Interlot variations of transition temperature range and force delivery in copper-nickel-titanium orthodontic wires.
abstract: BACKGROUND
  The manufacturing process for copper-nickel-titanium archwires is technique sensitive. The primary aim of this investigation was to examine the interlot consistency of the mechanical properties of copper-nickel-titanium wires from 2 manufacturers.
  
  
  METHODS
  Wires of 2 sizes (0.016 and 0.016 × 0.022 in) and 3 advertised austenite finish temperatures (27°C, 35°C, and 40°C) from 2 manufacturers were tested for transition temperature ranges and force delivery using differential scanning calorimetry and the 3-point bend test, respectively. Variations of these properties were analyzed for statistical significance by calculating the F statistic for equality of variances for transition temperature and force delivery in each group of wires. All statistical analyses were performed at the 0.05 level of significance.
  
  
  RESULTS
  Statistically significant interlot variations in austenite finish were found for the 0.016 in/27°C (P = 0.041) and 0.016 × 0.022 in/35°C (P = 0.048) wire categories, and in austenite start for the 0.016 × 0.022 in/35°C wire category (P = 0.01). In addition, significant variations in force delivery were found between the 2 manufacturers for the 0.016 in/27°C (P = 0.002), 0.016 in/35.0°C (P = 0.049), and 0.016 × 0.022 in/35°C (P = 0.031) wires.
  
  
  CONCLUSIONS
  Orthodontic wires of the same material, dimension, and manufacturer but from different production lots do not always have similar mechanical properties. Clinicians should be aware that copper-nickel-titanium wires might not always deliver the expected force, even when they come from the same manufacturer, because of interlot variations in the performance of the material.
authors.affiliation: Private practice, New York, NY. Electronic address: Georgios.Kanavakis@tufts.edu.
authors.forename: Renée C
authors.initials: RC
authors.lastname: Pompei-Reynolds
authors.affiliation: Assistant professor, Department of Orthodontics and Dentofacial Orthopedics, Tufts University School of Dental Medicine, Boston, Mass.
authors.forename: Georgios
authors.initials: G
authors.lastname: Kanavakis
mesh_terms: D002152:Calorimetry, Differential Scanning / Q000295:instrumentation; D003300:Copper / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D009969:Orthodontic Wires; D018583:Pliability; D011786:Quality Control; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D044366:Transition Temperature
chemical_list: C415948:Copper NiTi; D003722:Dental Alloys; C093826:Austenite; D003300:Copper; D009532:Nickel; D014025:Titanium