I do NOT have this issue but many do and I just sent this to to a kinda friend on magnesium, many are deficient...and you've got to relax more and those jaw muscles. I've been taking magnesium for decades and there is a mag deficiency in the U.S. for certain. The world, could be too.
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Ultimate Guide to Teeth Grinding and TMJ.
Here is the form of mag to be taken to relax jaws. Magnesium Glycinate