Influence of different storage temperatures on the mechanical properties of NiTi, Cu-NiTi and SS orthodontic archwires: An in vitro study Luca Friedli 1,1 , Prasad Nalabothu 1,2,1 , Carles Bosch 1 , Carlalberta Verna 1 , Markus Steineck 1 , Michel Dalstra 1 1. University Center for Dental Medicine UZB, Department of Paediatric Oral Health and Orthodontics, Mattenstrasse 40, 4058 Basel, Switzerland 2. University Hospital Basel, Department of Oral and Craniomaxillofacial Surgery, Basel, Switzerland Correspondence: Prasad Nalabothu, University Center for Dental Medicine UZB, Department of Paediatric Oral Health and Orthodontics, Mattenstrasse 40, 4058 Basel, Switzerland. prasad.nalabothu@unibas.ch ORTHO-489 Keywords Copper-NiTi NiTi wires Stainless steel Storage temperature Biomechanical testing Orthodontic wires Summary Objective > Due to their exceptional temperature sensitivity, the mechanical properties of Nickel- titanium and Copper Nickel-titanium wires may be influenced by their storage temperature. This in turn may have clinical implications and may also affect the outcomes. This study analyzed the influence of storage temperatures on the mechanical properties of orthodontic wires in a laboratory setting. Materials and methods > Stainless steel (SS), Nickel-Titanium (NiTi), and three variants of Copper- NiTi (Cu-NiTi 27 8C, 35 8C and 40 8C), 0.017 0.025 inches in size were analysed using a three- point bending test in a pre-heated chamber at 36 8C. The orthodontic wires were stored for twenty-four hours before the mechanical testing at four different temperatures (58, 228, 368 and 60 8C). Results > The obtained results showed that the mechanical forces exerted by 27 8C Copper-NiTi exhibit the most stable behaviour after having been stored at different temperatures, whereas 35 8C Copper-NiTi showed the highest variability. As to be expected, Stainless steel shows no changes in its bending mechanical properties. Conclusion > Furthermore, the results of this investigation reflect the importance of controlling the storage temperature of orthodontic NiTi and Copper-NiTi wires tested in a research environment in order to avoid unexpected bias. Available online: 1 Luca Friedli and Prasad Nalabothu are joint first authors and contributed equally to this work. To cite this article: Friedli L, et al. Influence of different storage temperatures on the mechanical properties of NiTi, Cu-NiTi and SS orthodontic archwires: An in vitro study. International Orthodontics (2020), https://doi.org/10.1016/j.ortho.2020.05.009 tome xx > 000 > xx 2020 https://doi.org/10.1016/j.ortho.2020.05.009 © 2020 CEO. Published by Elsevier Masson SAS. All rights reserved. 1 Original Article International Orthodontics 2020; //: /// Websites: www.em-consulte.com www.sciencedirect.com