My mom grinds her teeth and wears a mouth guard. I don't, apparently - the only time I did was one week about ten years ago, and the main symptom was an awful headache centered on my temples that was resistant to all drugs but one, whose name escapes me now. I figured out that it was from my teeth when I realized that tensing my jaw as if grinding led to flashes of greater pain in my temples. I stopped after a week, though, and I don't know why I haven't done it since.