X-ray diffraction study of low-temperature phase transformations in nickel-titanium orthodontic wires.

Area of Science:

• Materials Science
• Biomaterials Engineering
• Orthodontics

Background:

• Nickel-titanium (NiTi) alloys are crucial in orthodontics due to their superelastic properties.
• Understanding phase transformations in NiTi wires is essential for predicting their clinical performance.

Purpose of the Study:

• To analyze phase transformations in three clinically relevant NiTi orthodontic wire alloys using X-ray diffraction (XRD).
• To compare XRD findings with previous temperature-modulated differential scanning calorimetry (TMDSC) studies across a temperature range of 25°C to -110°C.

Main Methods:

• Conventional X-ray diffraction (XRD) was employed on three NiTi archwires: 35°C Copper Ni-Ti, Neo Sentalloy, and Nitinol SE.
• Samples were analyzed at temperatures including 25°C, -110°C, -60°C, -20°C, and 0°C.

Main Results:

• XRD results for phase identification at different temperatures aligned well with prior TMDSC studies.
• The presence of R-phase at 25°C was verified.
• New XRD peaks indicated low-temperature martensitic transformation, attributed to twinning via TEM.

Conclusions:

• XRD is a valuable tool for studying phase transformations in NiTi orthodontic wires.
• Optimal understanding is achieved by integrating XRD data with complementary TMDSC and TEM analyses.