Composition and in vitro corrosion of orthodontic appliances.

The high incidence of nickel allergy and the increasing use of nickel-containing dental biomaterials has been of growing concern. The purpose of this investigation was to analyze different types of alloys used in orthodontics, and to study whether nickel and chromium will be released from these alloys when stored in physiologic saline. Face-bows, brackets, molar bands, and arch wires were analyzed. Most of the different parts in the face-bows, brackets, and molar bands were similar to conventional 18/8 stainless steel. Except the wires, most appliances included a variable amount of silver solder, the greatest in face-bows. After 14 days in 0.9% sodium chloride (NaCl), the largest amount of nickel and chromium were leached out from the face-bows and the least amount from the arch wires. Soldered stainless steel face-bows seemed to be very susceptible to corrosion. The release of nickel seemed to be related to both the composition and the method of manufacture of the appliances, but the release was not proportional to the nickel content.