Publication: Ageing treatment effect on the bending behaviour of nickel-titanium archwires in orthodontic bracket systems
Loading...
Date
2024-08-01
Authors
Asad, Munir
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Superelastic nickel-titanium (NiTi) archwires have gained popularity as the
archwire of choice during the orthodontic alignment and levelling stages because of
their capacity to apply light force to the teeth. Generally, orthodontic treatment starts
with round archwires and subsequently progresses to rectangular archwires within 4-
6 weeks, ensuring a consistent bending force of approximately 1.0 N. However,
commercial NiTi archwires may cause discomfort because of their greater bending
force, which exceeds the recommended force for tooth movement. In this study, a
novel ageing treatment approach was used to alter the magnitude of the bending force
in commercially available superelastic NiTi archwires of various sizes.
This study examined three archwires with dimensions of 0.30, 0.40, and 0.40
× 0.56 mm. Subsequently, these archwires were subjected to various ageing
temperatures ranging fr om 370 to 550 °C for durations of 15, 30, and 45 min. The
archwires underwent thermal analysis, tensile testing, three-point bending testing, and
three-bracket bending testing after the ageing treatment. The study used the force deflection curve of aged archwires to evaluate force delivery parameters, and
regression models was created to predict the bending force of aged NiTi archwires in
orthodontic bracket assemblies. Differential scanning calorimetry (DSC) analysis
shows that the ageing treatment effectively alters the thermal transformation
temperature of commercial NiTi archwire, with longer durations leading to higher Af
temperatures. Furthermore, with ageing treatment, the unloading forces of the commercial NiTi archwire during the three-point and three-bracket tests were reduced
to lower magnitudes. The study found that ageing treatment reduced the maximum
unloading force of commercial archwire from 2.79 N to 0.21 N for aged rectangular
geometry during three-bracket bending, with less impact on round-shaped geometries.
The suitable ageing conditions for these archwires were 430–550 °C for 15 min for
0.30 mm, 370–550 °C for 30 min for 0.40 mm, and 400–550 °C for 45 minutes 0.40 ×
0.56 mm, respectively. The developed regression models yielded high R-squared
values of 0.9677, 0.7207, and 0.7083 and p-values < 0.05 for the loading force,
unloading force, and force difference, respectively. The ageing treatment could be
employed to improve the force delivery trends of commercial grade NiTi archwire by
reducing the magnitude of the force exerted on the teeth during the entire course of
orthodontic treatment.