The Effect Of Hydrogen Diffusion In Orthodontic NiTi Archwire
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Date
2022-07-24
Authors
Azaman, Amirul Fahmi
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The application Nickel-Titanium alloy has been widely used in orthodontics because of
its superior mechanical qualities, biocompatibility, ductility, corrosion resistance,
reduced elastic modulus, and specific features such as superelasticity and form memory
effect [1]. When utilized in orthodontic treatments, nickel-titanium alloy is frequently
exposed to the oral environment, which commonly causes fractures in the orthodontic
wires. In this project, the deformation behavior as well as the thermo-mechanical
properties of the NiTi superelastic wires has been investigated immediately after
charged with hydrogen and aged at different time intervals. The specimen’s mechanical
deformation behavior will be tested using the Universal Testing Machine (UTM) while
the thermo-mechanical behavior will be investigated using the Differential Scanning
Calorimetry (DSC). Experimental results show that compressibility and recovery of
orthodontic NiTi wires were dependent on the period which the wires were charged and
aged. From DSC analysis, the NiTi wires shows different behaviors with different
charging and ageing time. During both the reverse transformation and forward
transformation, the height of the peak and number of peaks for samples with different
charging time and ageing time are different in comparison with the as-received sample.
When charged for 24 hours and aged for 14 days, two peaks were obtained during the
martensite to austenite phase transformation which differs from the all the other
specimen which indicated two R-phase for that particular phase transformation.
Moreover, the deformation behavior obtained from the tests show that specimens that
were charged with hydrogen and aged at room temperature produced higher number of
deflection for the same value of bending force compared to the as-received specimen.
It is speculated that longer hydrogen charging and aging period will allow more
hydrogen to diffuse into the wire. This hydrogen diffusion affected the microstructure
of the NiTi archwire and caused the reduction in the elasticity of the wire.