title: Mechanical properties of different esthetic and conventional orthodontic wires in bending tests : An in vitro study.
abstract: OBJECTIVE
  The goal of this study was to determine the mechanical properties of different esthetic and conventional orthodontic wires in three-point and four-point bending tests, and in a biomechanical test employing three bracket systems.
  
  
  METHODS
  The behavior of round wires with a diameter of 0.46 mm (0.018″) were investigated: uncoated nickel titanium (NiTi) wires, surface modified NiTi wires; FLI®Orthonol Wire®and glass fiber reinforced plastic wires. The biomechanical bending test was performed using the following bracket types: metal brackets (Discovery®, Dentaurum), ceramic brackets (Fascination®, Dentaurum), and plastic brackets (Elegance®, Dentaurum). All bending tests were performed in the orthodontic measurement and simulation system (OMSS) at a temperature of 37 °C. The classical three-point bending test was performed according to an ISO standard (DIN EN ISO 15841:2007) using the appropriate thrust die and supports with a predefined span of 10 mm. In the other tests the supports or interbracket distances were chosen such that the free wire length was also 10 mm (5 mm between adjacent brackets). All wires were loaded centrally to a maximum of 3.1 and 3.3 mm in the biomechanical test, respectively. The force was measured upon unloading with a loading velocity of 1 mm/min. Each specimen was loaded twice and a total of 10 specimens tested for each product. Weighted means and the error of the weighted mean were calculated for each product.
  
  
  RESULTS
  Fiber reinforced wires displayed lowest forces in three-point bending with values of 0.4 N at a displacement of 1 mm and 0.7 N at a 2 mm displacement. In four-point bending the forces were 0.9 N and 1.4 N, respectively, at the same displacements. Almost all of the translucent wires showed fracture upon bending at displacements greater than 3 mm, independent of the bending test and bracket type. The different investigated NiTi wires, surface modified or conventional, only showed minor variation, e.g., 2.2 N for rematitan®Lite White and 2.0 N for rematitan®, 2.1 N for FLI®Coated Orthonol®and 1.7 N for Orthonol®in four-point bending. The rhodinized wire generated forces between these values (2.1 N).
  
  
  CONCLUSIONS
  The translucent wires had the lowest forces in all three bending tests; however, displacements above 3 mm resulted in increased risk of fracture. Forces of investigated NiTi wires were very high and in part above clinically recommended values.
authors.affiliation: Endowed Chair of Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr.17, 53111, Bonn, Germany.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Alobeid
authors.affiliation: Endowed Chair of Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr.17, 53111, Bonn, Germany.
authors.forename: Cornelius
authors.initials: C
authors.lastname: Dirk
authors.affiliation: Endowed Chair of Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr.17, 53111, Bonn, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Reimann
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Alberta, Edmonton, Canada.
authors.forename: Tarek
authors.initials: T
authors.lastname: El-Bialy
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Bonn, Bonn, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Jäger
authors.affiliation: Endowed Chair of Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr.17, 53111, Bonn, Germany. bourauel@uni-bonn.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Bourauel
mesh_terms: D000497:Alloys / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D055119:Elastic Modulus; D019544:Equipment Failure Analysis; D004954:Esthetics; D008422:Materials Testing; D016910:Orthodontic Brackets; D009969:Orthodontic Wires / Q000145:classification*; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D000497:Alloys; D003764:Dental Materials; C013616:nitinol
keywords: Mechanical properties; Nickel titanium; Orthodontic wires; Surface modification