Orthodontic recycling at the crossroads.

housands of orthodontic practitioners around the world currently recycle brackets, tubes, and bands. Nearly all recyclers, whether commercial companies or private clinicians, use heat and electropolishing. Heat is necessary not only to decontaminate and sterilize orthodontic attachments, but also to remove the adhesive's polymeric matrix. Heating stainless steel to between 350° and 800°C (650-1,600°F), the temperature range necessary for charring the adhesive, for more than 30 minutes leads to the alloy's sensitization—a segregation of chromium carbide at the boundaries of the grains. The depletion of structural chromium, along with the formation of a disrupting, acid-soluble film of carbides, renders the steel brittle and susceptible to intergranular corrosion, a condition considered "catastrophic" because it dramatically affects the alloy's strength. To remove the highly adherent dark layer of oxides and carbides that forms on the attachment surfaces after they have been subjected to heat, and to restore the luster of the metal, recyclers use electropolishing. Even in professional shops, however, electropolishing of such small and complex-shaped parts is difficult and inconsistent at best. Electropolishing tends to open the bracket slots, level the undercuts in the bases, and thin the power arms, the wings, and espe-