More and more frequently my 3 year old son is intentionally jutting his lower jaw forward, causing him to have an underbite. I'm worried he might cause problems for his teeth but if I try to say something to him about it of course he'll do it more...It's not a natural underbite, he never had one before, and it does not persist when he's at rest or speaking normally. I don't know what's up with him or how to curb this weird behavior...any advice?
I wouldn't worry about it. Young kids do all kinds of things for a short period. He may have just realized that he could do that. I wouldn't make a big deal about it unless he continues to do it for a long period of time.