So, I wrote back to them and said, "no, you are the manufacturer and I want to know from you." They eventually told me that they do not use plasticizers, but I asked 3 times if they used PVC at all. They answered the email, but refused specifically to answer the question. I wrote back and said that I will just assume that since they refuse to answer that I will assume that they do contain PVC. They did not respond.
So, I am just putting that out there. I don't want to cause a fuss. I personally couldn't put that material in contact with a mucous membrane for that long, but that's me. I also realize I am probably in big trouble when it comes time for me to get my retainer! LOL (and, no, I don't want to know what chemicals are in the bracket glue either!)
