Nickel-titanium alloys: stress-related temperature transitional range

Area of Science:

• Biomaterials Science
• Materials Engineering
• Orthodontics

Background:

• Nickel-titanium (NiTi) wires are crucial in orthodontics due to their superelastic properties.
• Mechanical stress can alter the transition temperature range of NiTi alloys, affecting their performance.
• Understanding these effects is vital for optimizing orthodontic treatment.

Purpose of the Study:

• To investigate the influence of mechanical stress on the transition temperature range of orthodontic NiTi wires.
• To evaluate the performance of different NiTi wire types under simulated clinical conditions.
• To identify suitable NiTi alloys for the aligning stage of orthodontic therapy.

Main Methods:

• Samples of Sentalloy, Copper Ni-Ti (27°C, 35°C, 40°C), and Nitinol Heat-Activated wires were tested.
• Wires were subjected to temperature cycles (4°C–60°C) under simulated dental crowding (minimum and severe).
• Electrical resistivity was used to monitor phase transformations.

Main Results:

• Induced mechanical stress displaced the transition temperature ranges toward higher temperatures.
• Copper Ni-Ti 27°C and Nitinol Heat-Activated wires demonstrated consistent superelastic behavior under maximum loading.
• The study confirmed stress-induced shifts in transition temperatures for tested NiTi orthodontic wires.

Conclusions:

• NiTi wire transition temperatures are sensitive to mechanical stress, impacting superelasticity.
• Copper Ni-Ti 27°C and Nitinol Heat-Activated wires are recommended for the aligning stage due to reliable performance under stress.
• Alloy selection should consider stress-related temperature shifts for optimal orthodontic outcomes.