there comes a time when most cats will require some dentistry at the vet. some animals, just like some people, simply have better (or worse) teeth than others. I like to have that detistry done before the cat gets too old that it is risky to be put under anesthesia. you can't brush away a build up, and tarter control food or treats will also not help a build up (they are for prevention). so if it needs to be done, do it sooner rather than later. and maybe the special diet and brushing will help KEEP them in good shape.