Yeah that's because they are similar to a retainer and need to be kept on about every day, or your teeth WILL move and they will be hard to put back on. I didn't have invisalign or anything, but I had braces in high school and they were followed by retainers (basically what invisalign is) I would say they probably work just fine, but you have to make sure your son is responsible enough to keep them on every day and not lose them or accidentally throw them out. I lost two pairs of retainers and I was 19 lol. Braces you can't take off and they don't give you a choice, which is better for kids, but everyone is different. Just make sure he's careful or you're going to be paying more than you want to replace them, or they wont work cause he'll forget to put them back in.
