Comparison of Loading and Unloading Behavior of Commercial and Locally Made Copper-Nickle-Titanium (NiTiCu) Orthodontic Archwire

Abstract

Background: Copper-nickel-titanium (NiTiCu) archwire has been favoured in clinical orthodontic practice because of its superior superelasticity (SE) and shape memory effect (SME) properties. Objective: To compare the loading and unloading behavior of commercial NiTiCu orthodontic archwire and locally made NiTiCu orthodontic archwire based on composition and mechanical properties especially in relation to percentage recovery, stress plateau, stress hysteresis, and loading and unloading slope. Materials and Methods: The materials used were divided into two categories: the NiTiCu (40°C) commercial Ormco brand (USA) archwires and the locally made NiTiCu archwires produced at King Mongkut University of Technology Thonburi (KMUTT). The samples were examined using an Electron Probe Microanalysis (EPMA) to test their chemical composition. For loading and unloading behavior the Universal Testing Machine (Instron) was used for the three-point bending test. The Mann-Whitney U test was employed to analyze and compare the data. Results: Chemical composition, there were significant differences in at.% of Ni, Ti, and Cr composition between commercial and locally made archwire. There was no significant difference in at.% in Cu. In terms of percentage recovery, there was a significant decrease in locally made archwire. For stress plateau and stress hysteresis, there were also significant increases in Thai-made archwire when compared with commercial archwires. In addition NiTiCu (Ormco) showed significantly less inclination than locally made NiTiCu archwire in both loading and unloading slopes. Conclusion: Based on the results of this study, the mechanical properties of the locally made archwires were not as suitable as the commercial archwires. This preliminary study provides useful information for the further development of locally made NiTiCu archwires. Therefore, the use of the NiTiCu should be considered on a case by case basis. This experiment was useful in comparing locally made NiTiCu wire and commercial orthodontic wire.