What is the difference between clear retainers and invisalign?

Not really.. invisalign is a series of clear trays that slowly move your teeth, clear retainers just keep them in the position they were when your braces were taken off. I think that maybe some refinements can be done with clear retainers, but that would mean you probably have several of them, in a series, each one slightly different than the last one - to accomplish the tweaking. Invisalign is pretty cool... I think now there are many cases that can be done using it, when it was more of a new concept/tool very few people qualified. Before you ask me - no I haven't used Invisalign lol. I had typical braces... I have non-clear retainers that are active, I don't like the idea of spit getting inside.