I had to make my bf go to the dentist. I was saying for weeks that he was grinding his teeth in his sleep and he didn't believe me. So he goes to the dentist and the first thing she says is "oh....you grind your teeth in your sleep".

Luckily he had a nice, molded mouth guard from when he played hockey and that has essentially stopped any pain he had. He also uses those cheap $5 ones from wal-mart sometimes. They don't last nearly as long but they do the job.

I don't know of anything you can do before bed to prevent it....never been a teeth grinder, myself.