They can also irritate the patient's tongue, which may hit them repeatedly. Most teens and children get stainless steel brackets because they're durable and less expensive than other kinds. These wires, made of nickel titanium alloys developed through the NASA space program, hold their shape better than stainless steel wires. As a result, they require fewer replacements and trips to the orthodontist, often shortening treatment time. Special-purpose appliances can correct specific problems, such as the roof of the mouth being too small.
Most patients wear a combination of two or more appliances over the course of treatment.
Elastics and retainers also come in an array of colors. It's even possible to put a logo or mascot on a retainer. The latest development, although not widely used, is magnets attached along the archwire to the upper or lower molars. Encased in stainless steel and placed with opposing or attracting forces, the magnets can help create or close spaces between teeth. In some cases, they can replace headgear, one of the most conspicuous orthodontic appliances.