With poor tongue posture, your tongue will push up against the back of your teeth when you swallow. It’s a very gentle push, but over time it can make your teeth crooked or fang them outward.

With your tongue laying across the roof of your mouth and the tip resting on the frontmost part, this pushing is non-existent.

This is how you should be drinking as well. It naturally prevents you from chugging your beverages.