Man's long history of technologic development has been marked by a continuing search for improved materials. This effort has resulted in vast arrays of new materials which have affected nearly every aspect of contemporary life, including orthodontics.Today orthodontists move teeth using fixed appliances fashioned from metals, ceramics, and polymers. Stainless steel, cobalt-chromium, nickel-titanium, and b-titanium are the main alloys used to fashion arch wires. Stainless steel has been the workhorse for generations; despite its heat-treatment capabilities, cobalt-chromium has remained a distant competitor. The two titanium-based alloys have found their market niches as well: nickel-titanium in the early stages of treatment and b-titanium in the intermediate stages of treatment. None of these materials is ideal, however. The first three alloys contain nickel, which is regarded by some as an allergen. Anecdotal reports ranging from edema of the tongue, lips, and mouth lining to anaphylaxis reach this laboratory some half-dozen times a year.