Straighten Teeth Clear Is It True That Some Orthodontists Can Use Retainers (Essix Ones) To Straighten Teeth Instead Of Invisilign?

Is it true that some orthodontists can use Retainers (Essix ones) to straighten teeth instead of invisilign? - straighten teeth clear

I know it would be much cheaper ... but I just wanted to make sure that it is a fact. But they are cheaper than invisilign clear! Anyone who has already done this method? Cost? Results?