The recycling of braces (brackets) involves removing the glue from the back of the brace by some process (burning it off, dissolving it with chemicals, etc.) and then re-using it on another patient. The companies that do this try to ensure that the properties of the braceket are not chenged by this process. They provide the orthodontist with a "slot keeper" to place in the bracket slot (that the wire fits into), so when the bracekt is removed from the tooth, the slot is not crushed or otherwise damaged as it usually is when the braces are removed. They check the dimensions of the slot before the bracket is sent back to the orthodontist.
I have always felt that patients expect that when they seek orthodontic treatment that only new materials will be used on them. I know that I would only want new materials used if I was undergoing treatment. In addition, since there is some debate as to what effect recycled brackets have on treatment, I have never considered using recycled brackets in my practice.