To portray the claim, I thought of a picture of a kid in a birthday party setting, completely covered in blue cake frosting (eyes closed, also covered) with only their perfectly clean teeth being exposed. Just like one of those hilarious youtube videos of kids making a mess. To complete the picture, I would have a cat sitting by the kid, also covered in frosting and wearing a birthday hat. The contrast between smile and mess would clearly show the "barrier between your teeth and the world".