Ni-Ti Superelastic Wire Coupled with Conventional Brackets During Bending Tests: Cross-section Effect Comparison

Ni-Ti shape memory alloy has become a famous alloy in the dental field. This alloy is used to design orthodontic wire suitable for the alignment stage. The Ni-Ti superelasticity has permitted to the clinicians to ensure an optimal orthodontic displacement during long period. The choice of round or rectangular cross section wire depended on the force delivered by the Ni-Ti wire, since this archwire exhibits a different mechanical behavior compared to an ordinary alloy. Thus, the aim of this work is to examine the effect of varying the cross-sectional dimension of superelastic Ni-Ti wire inserted in three brackets during bending tests which reproduce the most accurately the mechanical response of the wire as it is inserted in the oral cavity. The experimental findings showed that, when studying the cross-section size effect, the engagement loading, and the orthodontic force are dominated by the martensitic transformation process rather than the moment of inertia wherein the pseudo-elastic behavior is revealed. Moreover, the activation and deactivation loads have been affected by the brackets ligated system when comparing the experimental results to the literature ones. This was due to the friction resistance induced by the wire and the braces coupled with the ligatures.