ORIGINAL ARTICLE Mechanical properties of different esthetic and conventional orthodontic wires in bending tests An in vitro study Mechanische Eigenschaften verschiedener a ¨sthetischer und konventioneller kieferorthopa ¨discher Dra ¨hte in Biegeversuchen Eine In-vitro-Untersuchung Ahmad Alobeid 1 • Cornelius Dirk 1 • Susanne Reimann 1 • Tarek El-Bialy 2 • Andreas Ja ¨ger 3 • Christoph Bourauel 1 Received: 5 February 2016 / Accepted: 2 November 2016 Ó Springer Medizin Verlag Berlin 2016 Abstract Aims The goal of this study was to determine the mechanical properties of different esthetic and conven- tional 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 00 ) were investigated: uncoated nickel tita- nium (NiTi) wires, surface modified NiTi wires; FLI Ò Orthonol Wire Ò and glass fiber reinforced plastic wires. The biomechanical bending test was performed using the fol- lowing bracket types: metal brackets (Discovery Ò , Den- taurum), ceramic brackets (Fascination Ò , Dentaurum), and plastic brackets (Elegance Ò , Dentaurum). All bending tests were performed in the orthodontic measurement and sim- ulation 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 dis- tances 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 modi- fied or conventional, only showed minor variation, e.g., 2.2 N for rematitan Ò Lite White and 2.0 N for rematitan Ò , 2.1 N for FLI Ò Coated Orthonol Ò and 1.7 N for Orthonol Ò in four-point bending. The rhodinized wire generated for- ces between these values (2.1 N). Conclusion 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. Keywords Orthodontic wires Á Nickel titanium Á Surface modification Á Mechanical properties Prof. Dr. Christoph Bourauel. & Christoph Bourauel bourauel@uni-bonn.de 1 Endowed Chair of Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr.17, 53111 Bonn, Germany 2 Department of Orthodontics, School of Dentistry, University of Alberta, Edmonton, Canada 3 Department of Orthodontics, School of Dentistry, University of Bonn, Bonn, Germany 123 J Orofac Orthop DOI 10.1007/s00056-016-0078-5