I didn't know until I married Tetsu that he ground his teeth. He's a pretty serious grinder. There was one summer when my mother visited us and though we slept with a sliding paper door separating us, one night my mother slid open the door and peered down at us.
"Tani. I think there's a frog by Tetsu's pillow. Listen."
"Um... No. That's Tetsu grinding his teeth."
Tetsu woke up about then and was surprised to see his new mother-in-law squatting on the floor beside him looking down into his face (we're sleeping on futon.) I explained that my mother had thought she heard a frog.
"Your mother looks sort of a like a frog squatting there." and he rolled over and went back to sleep.
So I've lived with grinding in my ear for 30 some years. (And snoring... and irregular breathing... Tetsu's a noisy sleeper.)
About a week ago, Tetsu pointed out that he'd chipped his front tooth and Saturday he went to the dentist to have it repaired. He came back so pleased at how nicely his tooth had been fixed and he said that the dentist thought it might have been a stress break from teeth grinding.
"How can anyone chip their teeth when they're sleeping?"
I, on the other hand who know his habits, thought it was highly possible.
That was Saturday.
This morning (Monday) Tetsu woke up and swore slightly.
"Oh no. Look! That tooth I had fixed is chipped again! I must have done it in my sleep last night."
Tetsu is off to the dentist again today...
As I say, he is a pretty serious grinder... Grr-ibbet, grr-ibbet.