I've been grinding my teeth in my sleep since I was a little girl. Only a few years ago did I have a dentist who was alarmed at the extent of it, and made me a night guard which sort of clips onto my front two teeth. I wore that one down over the course of several years.
Last summer (pre-PTSD), I had a new one made. Since PTSD, I have ground on that one so badly that my lower front teeth have worn down to the point where they don't touch my uppers anymore. I try to bite together, and they don't meet. Now I wear a guard on my lowers too, although the damage is already done.