Bruxism Revisited

There's a few threads on this, I'm aware.

Is magnesium the only answer here? if so what type is best?

Met with an IAOMT Dentist today. I explained the muscles or glands (unknowing) behind my jaw were sore. He told me it's due to clenching and grinding and tried to sell me a mouthguard for a cool $775. I do agree that the grinding is a problem, just not sure if a mouth guard is the solution.

Also, when I asked about decay he explained that it's from not flossing. However, I floss twice a day, rinse with wright salt, baking soda, Biotene and oil pull. My gut tell's me it's my gut bacteria (no pun intended). Or maybe metals? Would like to get to the bottom of this decay because at the rate I'm going I won't have any teeth left soon. Also, my mother lost all of her teeth FWIW.