Hi, you seem to be saying your kitty grinds his teeth at night, like some people do? I have this problem and have had for many years. Of course it's not the best thing for the teeth and I have never found an adequate solution. Since I believe the most frequent cause (at least in people) is nervous tension and/or other psychological issues, I am surprised to hear that your kitty is doing it. Animals seem so blessedly free of angst and neuroses (at least most of the time). Maybe he chipped a tooth? My dentist said that tooth grinding can also occur when there is a problem with your bite, how your teeth fit together, etc. I would consider at least calling the vet if not taking kitty in for a look-see...Anyhow, I hope you and kitty have better luck with this than I have had...Love from MARTHA and Julie ("meow") the California Calico Princess