Mechanical Properties and Potential Clinical Implications of Improved Superelastic Orthodontic Archwires: An Observational Study

Background: Superelastic materials have gained popularity due to their ability to maintain a constant force over a prolonged period during orthodontic treatment. However, high hysteresis and frictional properties had limited the use of superelastics as archwire material that demanded the need for improved superelastic orthodontic archwires with enhanced mechanical properties.

Aim: The present study aimed to investigate the differences in mechanical properties and frictional resistance of improved superelastic orthodontic archwires against conventional archwires and to evaluate their potential implications in clinical orthodontic practice.

Materials and methods: A total of 45 samples with 15 in each category respectively from low hysteresis superelastic archwire (L&H Titan; Tomy Inc., Tokyo, Japan), nickel-titanium (NiTi) archwires (Ormco, Brea, CA, USA) and NiTi with copper (CuNiTi) archwires (Ormco) of equal diameter (0.016 x .022 inches) and length (10 cm) were randomly assigned in combination among metal and ceramic orthodontic brackets group. The frictional properties of the archwires were measured using a universal testing machine (Instron, Norwood, MA, USA) equipped with a custom-made jig. The load-displacement data were recorded, and other mechanical properties that included tensile strength, compressive strength and deflective force at 4mm were also evaluated. The data were analysed using independent Student t-tests to compare the mean frictional resistance of the three archwires followed by analysis of variance (ANOVA) to evaluate differences between the means with p-value of less than 0.05 considered as statistically significant.

Results: The improved superelastic wires had the least frictional resistance among the three archwires tested. Further intergroup comparison to evaluate differences between the frictional resistance means among the three archwire categories with two orthodontic brackets groups revealed a significant difference at p<.05. Pairwise comparison also showed significant differences with higher frictional resistance between metal brackets and low hysteresis superelastic archwire category than ceramic brackets and NiTi with copper archwires (.0003) and ceramic brackets with NiTi archwires category (.003) respectively. The lowest deflective force at 4mm with better tensile and compressive strength was seen with the improved superelastic wires.

Conclusion: The results of this study suggest that low hysteresis superelastic archwires have lower frictional forces when combined with metal orthodontic brackets compared with ceramic orthodontic brackets. Better tensile strength with least compressive strength and deflective forces at 4mm of testing among low hysteresis L&H Titan superelastic archwire than CuNiTi and NiTi archwires was observed making them potentially advantageous for orthodontic applications.