Braces wire is made from metal alloys, with the three most common being stainless steel, nickel titanium, and beta titanium. Your orthodontist will likely use all three at different points during treatment, switching materials as your teeth move and your needs change. Each alloy behaves differently, and that behavior determines when and why it’s used.
Stainless Steel
Stainless steel is the oldest and most recognizable orthodontic wire material. A typical orthodontic stainless steel wire (classified as type 304) contains 17 to 20% chromium, 8 to 12% nickel, less than 0.15% carbon, with iron making up the rest. The chromium is what makes it “stainless,” forming a protective layer that resists corrosion inside your mouth.
Stainless steel is the stiffest of the three main wire types. That stiffness is a disadvantage early in treatment, when teeth are still crooked and need gentle, consistent pressure. But it becomes an advantage later. During space closure and finishing, when teeth need to hold position or move in controlled ways, a rigid wire prevents unwanted shifting. Orthodontists can also bend stainless steel into precise shapes, making fine adjustments that softer wires won’t hold.
To get around the stiffness problem in early treatment, manufacturers make multi-stranded stainless steel wires. These are several thin steel wires braided or twisted together, which dramatically reduces rigidity. Research shows braided stainless steel wires perform about as well as nickel titanium for initial alignment.
Nickel Titanium
Nickel titanium wire, often called NiTi, is roughly 50% nickel and 50% titanium. It’s the wire most often placed first, when your teeth are at their most misaligned. NiTi is so elastic that even when bent into a severe curve to fit into a crooked bracket, it returns to its original shape and pulls your teeth along with it.
What makes this possible is a property called superelasticity. The metal has two distinct crystal structures, and it can shift between them under stress. When you bend the wire, its internal structure transforms at the molecular level. When the stress is released, it snaps back. This means the wire delivers a steady, gentle force over a long period rather than a strong initial force that quickly fades. For patients, that translates to less discomfort and more efficient tooth movement in the early months.
Some NiTi wires are also “heat-activated,” meaning they become more flexible at room temperature and stiffen as they warm up to body temperature inside your mouth. This makes them easier for the orthodontist to place and lets them activate gradually. Studies comparing heat-activated and standard superelastic NiTi wires, though, have found no significant difference in how quickly they align teeth during the initial stage.
Copper Nickel Titanium
A variation called copper nickel titanium (CuNiTi) adds about 5 to 6% copper to the mix. Copper is an efficient heat conductor, so these wires have more precisely defined transition temperatures. That matters because it means the force the wire delivers is more consistent from one end of the arch to the other. CuNiTi wires are manufactured at specific activation temperatures (27°C, 35°C, and 40°C), giving orthodontists finer control over when and how the wire starts working. Adding copper also increases mechanical strength and reduces permanent deformation, so the wire better maintains its shape over time.
Beta Titanium
Beta titanium wire, sometimes called TMA (titanium molybdenum alloy), was introduced for orthodontic use in 1979. Its composition is roughly 79% titanium, 11% molybdenum, 6% zirconium, and 4% tin. For years, a single manufacturer held the exclusive patent, but multiple versions are now available.
Beta titanium sits between stainless steel and nickel titanium in stiffness. It’s rigid enough to control tooth position precisely, but flexible enough to be bent into loops and small adjustments. That combination makes it particularly useful during the middle and later stages of treatment, especially for closing gaps. It’s also a practical option for patients with nickel allergies, since it contains no nickel at all.
Not all beta titanium wires behave the same way. Testing has shown that some brands are noticeably more flexible, with a smaller gap between the force applied when bending and the force returned when releasing. Others are stiffer and better suited for treatment phases that require loops or complex bends.
Wire Shape and Size
The material is only part of the equation. Orthodontic wires also come in different cross-sectional shapes: round, square, and rectangular. Round wires are typically used first. They slide easily through brackets and allow teeth to tip into rough alignment. As treatment progresses, your orthodontist switches to square or rectangular wires. These fill more of the bracket slot and control not just where a tooth sits but how it’s angled and rotated.
Within any given material, stiffness increases with the wire’s cross-section, particularly its height. A thicker rectangular stainless steel wire delivers dramatically more force than a thin round one of the same alloy. This is why treatment follows a general sequence: thin, round, flexible wires for initial alignment, progressing to thicker, rectangular, stiffer wires for fine-tuning and finishing.
Tooth-Colored and Coated Wires
For patients who want a less visible look, especially those with ceramic or clear brackets, coated wires offer a cosmetic alternative. The wire underneath is typically nickel titanium or stainless steel, with a tooth-colored layer applied over it. The three main coating types are epoxy resin, Teflon, and rhodium.
Performance varies considerably. Epoxy resin and Teflon coatings tend to degrade in the mouth. They can change color, corrode, and peel away from friction and chewing forces, eventually exposing the metal underneath. Rhodium coating, borrowed from jewelry manufacturing, holds up better. It shows less color change and less corrosion than the other options, and patients in studies rated it the most attractive of the three.
The trade-off with any coated wire is that the coating adds thickness, which can increase friction between the wire and bracket. That friction can slow tooth movement slightly compared to an uncoated wire of the same material.
Nickel Allergy Considerations
Nickel is present in two of the three main wire types: stainless steel (8 to 12%) and nickel titanium (about 50%). For the estimated 10 to 20% of the population sensitive to nickel, this is worth discussing with your orthodontist before treatment starts. Nickel-free braces and wires, defined as containing 2% nickel or less, appear to be a viable alternative. Beta titanium is the most common nickel-free archwire option, and some manufacturers produce nickel-free stainless steel brackets as well.