I bought whitening trays for my mother two years or so ago and I used the same service I had used previously for my own set (DDSwhite). Looks like their website has changed (
http://stores.dentist-whitening.com/-strse-Custom-Trays-cln-Trays-Only/Categories.bok). I haven't used this new website but I was happy to do business with the company in the past and never had any issues. Looks like there's a phone number so you should be able to call and get whatever information you need.
I originally whitened my teeth to remove stains that had been left from dental work when I was younger (mostly tiny marks left over from braces). I haven't whitened my teeth in probably two years now and noticed stains forming in some of the old places where the braces had probably removed some of the outer enamel. Too bad I can't find my trays now -- might order another set.
Edit: seems like Amazon has a lot of vendors now too.
Edited by why - 1/22/13 at 5:43am