title: Mechanical properties of orthodontic wires derived by instrumented indentation testing (IIT) according to ISO 14577.
abstract: BACKGROUND
  The aim of this study was the characterization of mechanical properties of representative types of orthodontic wires employing instrumented indentation testing (IIT) according to ISO 14577.
  
  
  METHODS
  Segments were cut from ten wires. The first six are made of stainless steel (SS), two are made of Ni-Ti, and the last two are made of titanium molybdenum alloys (TMA). Then, the Martens hardness (HM), the Vickers hardness (HVIT) based on indentation hardness (H IT), the indentation modulus (E IT), the ratio of elastic to total work (η IT), and the traditional Vickers hardness (HV1) were measured by IIT. The results were statistically analyzed by one-way ANOVA followed by Student-Newman-Keuls (SNK) test at a = 0.05. The HVIT and HV1 data were analyzed by paired t test (a = 0.05).
  
  
  RESULTS
  SS wires showed the highest hardness followed by TMA and Ni-Ti alloys. However, all wires showed significantly lower HVIT compared to corresponding HV1, a finding probably appended to elastic recovery around the indentation. E IT for all wires tested was determined much lower than the nominal values of the corresponding alloys due to the implication of residual stress field at the slope of unloading curve. Elastic to total work ratio was ranged from 45.8 to 64.4 % which is higher than that expected for ductile alloys (<30 %).
  
  
  CONCLUSIONS
  The products tested illustrated significant differences in their mechanical properties. Although IIT provides reliable data for hardness and elastic index of materials tested, the intense residual stress field developed during the manufacturing process significantly affects the determination of modulus of elasticity.
authors.affiliation: Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Thivon 2 str., Goudi 11527, Athens, Greece, szinelis@dent.uoa.gr.
authors.forename: Spiros
authors.initials: S
authors.lastname: Zinelis
authors.forename: Youssef S
authors.initials: YS
authors.lastname: Al Jabbari
authors.forename: Marianna
authors.initials: M
authors.lastname: Gaintantzopoulou
authors.forename: George
authors.initials: G
authors.lastname: Eliades
authors.forename: Theodore
authors.initials: T
authors.lastname: Eliades
mesh_terms: D000465:Algorithms; D000497:Alloys / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry*; D055119:Elastic Modulus; D004548:Elasticity; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D055595:Mechanical Phenomena; D009532:Nickel / Q000737:chemistry; D009969:Orthodontic Wires; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D000497:Alloys; D003722:Dental Alloys; C525450:titanium molybdenum alloy; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium