archwire

An archwire is a flexible metal wire that runs through the slots of orthodontic brackets fixed to the teeth. Together with brackets and ligatures, it forms the orthodontic appliance and provides the principal source of controlled forces that move teeth during treatment. Archwires are typically attached to braces using ligatures or self-ligating brackets and are periodically swapped as teeth move.

Common archwire materials include stainless steel, nickel-titanium (NiTi) alloys, and titanium-molybdenum (beta-titanium, TMA). NiTi wires exhibit shape memory and superelasticity, delivering gentle, continuous forces over a range of tooth movements. Stainless steel wires are stiff and durable, providing strong control, especially for later treatment stages. Beta-titanium wires balance formability with stiffness. Some wires incorporate additional elements for corrosion resistance and biocompatibility.

Wires vary in cross-section and size. Round wires (e.g., 0.014 to 0.020 inches in diameter) are commonly used for initial alignment, while rectangular or square wires (e.g., 0.019 × 0.025 inches) are used to control torque and finer tooth positioning. The wire is threaded through bracket slots and held in place by ligatures or by self-ligating brackets. In many systems, wires are exchanged and progressed through a sequence of sizes and materials over the course of treatment.

Clinical considerations include managing friction at the bracket-wire interface, adjusting wire progression to achieve desired tooth movement, and monitoring for patient comfort and hygiene. Archwires can be thermoactive, changing stiffness with temperature, particularly NiTi variants, and are selected to suit the treatment stage and patient needs.