Journal of Research in Dental and Maxillofacial Sciences

en Force Degradation Properties of Two Nickel-Titanium Closed Coil Springs orthodontic orthodontic Original article Original article <div style="border:solid windowtext 1.0pt; padding:1.0pt 4.0pt 1.0pt 4.0pt"> <div> <table align="center" hspace="0" vspace="0"> <tbody> <tr> <td style="padding: 0cm 12px; text-align: justify;" valign="top">Background and Aim: The aim of this study was to compare two nickel-titanium (NiTi) closed coil springs (CCSs) from two different manufacturers regarding their force degradation over 4- and 8-week periods.    Materials and Methods: In this in vitro experimental study, 20 NiTi CCSs from 3M® and GAC® were compared. The springs were extended until a tensile strength of 250 g was achieved, and the length of springs was recorded. They were then mounted on customized jigs according to the registered length, so as to keep them extended constantly. Springs from each manufacturer (n=10) were randomly divided into two subgroups (n=5): one subgroup was stored in artificial saliva and the other was stored in a dry environment. The forces were assessed 4 and 8 weeks later. Data were analyzed by repeated measures ANOVA and the Tukey post-hoc test (alpha=0.05). Results: The mean force of 3M® CCSs significantly decreased by 56% after 4 weeks and 14% after 8 weeks in dry condition, and by 46% after 4 weeks in wet environment; however, after 8 weeks in wet environment, the force decay was insignificant. The changes in force of GAC® CCSs in dry environment after 4 weeks and 8 weeks were not significant, indicating a constant force property. However, in artificial saliva, a statistically significant yet mild increase in force level was recorded. Conclusion: The results showed a force decay for the 3M® CCSs after 4 weeks while for the GAC® CCSs, an almost constant force level was observed even after 8 weeks. </td> </tr> </tbody> </table> </div> </div> Orthodontics, Dental Alloys, Orthodontic Appliance Design, Artificial Saliva 196 202 http://jrdms.dentaliau.ac.ir/browse.php?a_code=A-10-572-1&slc_lang=en&sid=1 Alireza Jafari-Naeimi jafariorthodclinic@gmail.com 100319475328460012019 000000024628944x Yes Department of Orthodontics, Dental Faculty, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran Elahe Rabiee elahe_rabiiee@yahoo.com 100319475328460012020 0000000172632144 No Department of Orthodontics, Dental Faculty, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran Zohre Hajipour zohrehajipour1@gmail.com 100319475328460012021 0000000215088231 No Department of Orthodontics, Dental Faculty, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran Farzaneh Hosseini dr.seyedeh.farzaneh.hosseini@gmail.com 100319475328460012022 0000000188221622 No Private Dentistry Practice, Tehran, Iran Elham Sayanjali Elham.sayanjali@iau.ac.ir 100319475328460012023 0000000152260953 No Department of Orthodontics, Dental Faculty, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran