Foreword. Innovations and new technologies in bonded orthodontic retainers: putting the different wires into...

The choice of retainer wire is crucial to ensuring long-lasting orthodontic results. Beyond simple mechanical retention, it must meet specific requirements in terms of design, physical properties, and biocompatibility. To date, there is no consensus on the best material, and new generations of wires continue to emerge to address the limitations of existing systems.

This article aims to describe and compare various types of retainer wires, whether they are shaped manually, such as Respond and Ortho-Flextech, or produced using a robotic process, such as Memotain, TMA Winnove Medical, or PolyEther-Ether-Keton (PEEK) wire.

The "ideal wire" should ensure a custom fit, appropriate mechanical properties, smooth surface quality, biocompatibility, durability, and acceptable aesthetics. Current options include chairside wires (Respond and Ortho-FlexTech), CAD/CAM or robot-made retainers (laser-cut NiTi Memotain and robot-bent TMA Winnove), and milled PEEK devices. Each option involves trade-offs: adaptability and flexibility versus rigidity and control; isotropy of round sections versus anisotropy of square sections; and added costs and logistical demands associated with digital workflows.

In multistranded wires, Young's modulus (E) corresponds to that of the base alloy; clinical stiffness depends instead on the effective EI (geometry, compaction, and inter-strand slip). Clinical success also relies heavily on bonding quality: thin, even resin layers and short spans between composite pads are as important as the wire itself. Overall performance therefore results from the synergy of wire, adhesive, and clinical technique.

Future developments are likely to focus on increased robotization, adhesive optimization, and the use of high-performance polymers. However, no current solution can yet be considered flawless.