Can plaque on a cat's teeth cause sneezing?

Yes, one of the reasons being an allergic reaction to the plaque causing sneezing.  Untreated, plaque can cause gum disease, tooth loss, sinus infections, heart problems to name a few. To avoid these serious problems, brush your cat's teeth 2-3 times a week. Have your veterinarian check your cat's mouth regularly. And of course, if you suspect something is wrong, take the cat to the vet immediately so that treatment can begin before something serious develops.