Impact of recycling on the mechanical properties of nickel-titanium alloy wires and the efficacy of their reuse after cold sterilization

This study aimed to assess the feasibility of reusing nickel-titanium (NiTi) alloy wires after 6 weeks of intraoral use by evaluating the changes in the load-deflection properties and surface characterization of these alloy wires after cold sterilization by immersion in 2% of acidic glutaraldehyde for 10 h. Twenty wires each in three groups of G1-as-received wires (ARW), G2-unsterilized used wires, and G3-sterilized used wires (SUW) were tested by the three-point bending test and scanning electron microscopy (SEM). The data were subjected to statistics, one-way analysis of variance, and Bonferroni posthoc test for comparison. Recycling of NiTi wires produced statistically insignificant changes in both the loading and unloading properties of the wires. The forces needed to twist the used wires, that is, G2-(UUW) and G3-(SUW) were lower than G1-(ARW), suggesting lowering of the stiffness of the wires. Superelasticity is well-maintained by G2-(UUW) and G3-(SUW) although there is an insignificant lowering of the forces exerted by them during loading and unloading. SEM demonstrated no increase in the pitting of surfaces in both G2-(UUW) and G3-(SUW); multiple areas were seen to be more smoothened over G2-(UUW) and G3-(SUW) NiTi wires surfaces. The findings of this study support the reuse of NiTi wires after 6 weeks of use in oral conditions followed by cold sterilization by immersion in 2% acidic glutaraldehyde for 10 h.