I also experience jaw tension. I inadvertently found out that magnesium help A LOT. I started taking Natural Calm, a fizzing, highly bio-available magnesium supplement for anxiety and as a sleep aid.
WOW.:shock: Not only did it help with my anxiety and sleep, it gave me crazy, fun dreams as well! I highly recommend this form of magnesium. It tastes great and the sweetened product is made with Stevia. I like the raspberry-lemonade flavor the best. I got the kind without Calcium because I get enough from my diet and too much calcium can be a bad thing, plus it's not needed to absorb the magnesium.
Here it is:
http://www.amazon.com/Natural-Vitality-Calm-Rasp-Lemon-powder/dp/B000WVY4PE