title: Load-deflection characteristics of superelastic nickel-titanium orthodontic wires.
abstract: Previous mechanical testing of orthodontic wires has, in many cases, failed to simulate some key features of the clinical environment. The purpose of this study was to investigate the load-deflection characteristics of 7 different 0.016-in initial alignment archwires (Twistflex, NiTi, and 5 brands of heat-activated superelastic nickel-titanium [HASN]) with modified bending tests simulating a number of conditions encountered clinically. Load-deflection tests were carried out on the wires with 5 different model designs, and data from selected points on the unloading phase of the generated graphs were statistically analyzed. Wire deflection was carried out at 3 temperatures (22.0 degrees C, 35.5 degrees C, and 44.0 degrees C) and to 4 deflection distances (1 mm, 2 mm, 3 mm, and 4 mm). Rankings were derived according to statistically significant differences in each test situation. The effects of model, wire, and temperature variation were all statistically significant. Twistflex and the 5 HASN wires produced a range of broadly comparable results, and NiTi gave the highest unloading values. Model rankings indicated that self-ligating Twin-Lock brackets produced lower friction than regular edgewise brackets. The authors recommend using the rankings from the mechanical test simulations to predict possible clinical performance of archwires.
authors.affiliation: Department of Oral Sciences and Orthodontics, University of Otago, Dunedin, New Zealand.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Wilkinson
authors.forename: Peter S
authors.initials: PS
authors.lastname: Dysart
authors.forename: James A A
authors.initials: JA
authors.lastname: Hood
authors.forename: G Peter
authors.initials: GP
authors.lastname: Herbison
mesh_terms: D000497:Alloys; D000704:Analysis of Variance; D003300:Copper; D003722:Dental Alloys; D003799:Dental Stress Analysis; D004055:Differential Thermal Analysis; D004548:Elasticity; D004867:Equipment Design; D008422:Materials Testing; D009532:Nickel; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D018583:Pliability; D018709:Statistics, Nonparametric; D014025:Titanium
chemical_list: D000497:Alloys; D003722:Dental Alloys; C040654:titanium nickelide; C013616:nitinol; D003300:Copper; D009532:Nickel; D014025:Titanium