Chemo did the same thing to me.I used a mouthguard for a month or so a while back to help with jaw pain I was experiencing. It had no effect on my tinnitus. I'll add that my tinnitus got like twice as bad when I went on chemo a few years back. It was pretty much instant, as soon as they plugged me in, and it never got better. It's now louder than the two fans, and almost drowns them out. I've become pretty used to it over the past few years. Don't get me started on migraines...
Either that or the radiation. But I’ve had tinnitus ever since. But hey, I’m still here to complain about it so guess it worked out for the best.