I have a guard from a company called NTI. It’s a small piece of acrylic that sits on my upper front teeth and has a sort of “shelf” that my lower incisors rest on. This apparently tricks the brain into refusing to clench down because at a deep level it knows not to bite when it’s incisor on incisor.
I recall reading that this style of night guard, while certainly better than a whole tooth guard that still allows you to grind but just protects your teeth, is not great for long term. However I can’t recall why and I need to research more. In any case I’ve been using mine for over 10 years and I would never go back to not using it.
Anyway, a bunch of unsolicited info that will maybe help you or anyone suffering from migraines who stumbles across this post.
After a while I noticed that my front teeth were not coming together any more when biting, and I could not force them together. It turns out it is known that for people that really force their jaws together, the NTI device actually changes and collapses the jaw joint, changing the pivot point of your whole jaw.
I stopped using it, but the change is permanent. I had to have the dentist actually grind down my molars so that my front teeth could touch again. Beware.