Hi! I get this too! I personally think it’s the inflammation from the heat innervating the trigeminal nerve – the bottom branch affects sensation in your teeth. Do you get any other face pain? Does it happen at other times? Inversions are the worst for me – I think it’s all the blood flow to the head – again pressing on the nerve cauicau pain. Let me know if it still bothers you or has gone away. Cheers!