Cats can get decayed teeth...some breeds are prone to tooth problems, such as Oriental Shorthairs.
My mom has my late sister's two lilac points, and they have just several teeth left each!
Please get a second opinion on your cat - maybe a friendly vet can show you where the decay is - if there is any - so you don't have to just take someone's word for it.
"Common sense and a sense of humor are the same thing, moving at different speeds. A sense of humor is just common sense, dancing." -- William James