The only time one of our pets had problems with her teeth, is when it became overgrown, and out of place. She had to be put under anesthetive it, but sadly could not take the anesthetic and died a few hours later. Very upsetting.
My dog only has dry kibble with occasional left-overs, and home-made treats, and every now and then a rawhide chew. While the vet can't tell exactly how old she is (somewhere between 10 and 14) her teeth are in excellent condition.