I am excited about using Invisalign and have signed up and waiting for the first aligners. But I'm now worried about having plastic in my mouth for 1+ years. I've tried to research its safety and composition.. The company refuses to talk to consumers directly about it, (in fact they are quite rude) which makes me more nervous. Is there any information or studies on the safety of the plastic, where it manufactured, what chemicals does it leach? Thank you! Sam