Out of curiosity, even if you do it for less than an hour a day as an adult? I don’t think it’s a good idea, but I’d be surprised if occasionally doing it after your bones have finished growing would cause huge problems. I don’t know anything about dentistry or anything relevant though, so I could totally be wrong.
More powerful tool to initiate a parasympathetic response while also toning your buccalis: closing your mouth and pinching your nose and exhaling to puff out your cheeks while bearing down like you're trying to take a shit (post)
(Don't start doing this just because you read it in a shit posting community or you may pass out)