I do this when I'm on the loo :)
Dr Svoboda mentioned that the function of apana vayu, the elimination energy of Vata dosha, is to pull downwards.
And since, when you're on the loo, the energy is trying to remove the waste, it can also loosen your teeth.
So he recommends clenching your teeth when you're doing your business.
So the rest room is a misnomer, I'd advise actively holding onto your teeth!