Vertical loops incorporated in an orthodontic wire create a segment of wire with increased length and reduced cross-sectional stiffness. This design allows the wire to bend more easily under force, thereby increasing its flexibility. Enhanced flexibility enables the application of lighter, more controlled forces, which is essential for effective tooth movement while minimizing patient discomfort and root resorption. In contrast, a straight wire without loops is inherently more rigid and transmits stronger forces. Therefore, loops serve as mechanical stress breakers, optimizing orthodontic wire performance.

Reference: Orthodontics: Current Principles and Techniques, 6th Edition.