Bruxism and Magnesium
Avoid magnesium oxide and focus on citrate or chelate. Also add calcium (to prevent loose stool), potassium (to increase absorption), vitamin B5 (to aid relaxation) and vitamin C.
https://www.proteethguard.com/blog/costeffective-treatments-for-teeth-grinding-bruxism/
http://www.christinatidwell.com/blog/2016/7/8/the-daily-grind
https://draxe.com/magnesium-supplements/