Hello and welcome to pet ,lovers!
This sounds like FORL, Feline Odonoclastic Resorptive Lesions, that chattering is a classic symptom.
this is a very painful condition and your kitty will need dental surgery, the sooner the better.
I have a cat who had the surgery last year. He was like a new cat, a kitten again, afterwards. I had had no idea how much pain he was in.
In addition to the pain he is in, untreated dental problems can cause other health problems such as kidney disease. Best to get him in to see the vet asap.
Please come back and let us know what happens.