Ditto what Becky said. The type of food you are feeding can and possibly is a large contributer to the dental problems. Evaluate your food. If it has a lot of grains in it and especially if grain, that being rice, wheat or corn, are the first ingredients on the list, or, if there is only one or two "meat" sources listed first, then a whole host of grains, switch foods. Grains, when digested, turn to sugar which is not only bad for the dog's system as a whole, they are empty carbs that the dog can not properly utilize. In addition, check the size of your kibble. If it is small, ditch it. A dog (and cat) need to be able to *chew* their food in order for their teeth and jaws to receive a proper workout and cleaning as well as for the digestive enzymes in their stomaches to get a kick start while the dog is eating.
IMO, be wary of "prescription" foods from a vet. There is a world of "evidence" as to what these so called "healthy" foods that are "prescribed" by vets *really* are and what they really do to an animal....as well as plenty of "evidence" as to *why* vets "prescribe" them in the first place (it's NOT for the health of the animal ).

Honesty, the single best thing you can do for your dog... if her teeth can handle it, is to get some chicken legs or beef/pork ribs and give her one of those a couple times a week...RAW... *don't* cook it and let her eat the entire leg or naw on the ribs until all meat is gone and the ends of the bones have been chewed off, then throw the rest of the rib bone away. Do not let *any* dog eat an entire rib bone. They are weight bearing bones and are too hard on a dog's teeth.

Letting your dog have something to actually *chew* on will help immensely in getting and keeping their teeth clean as well as strengthening their jaws and freshening their breath, especially since bad breath is caused by the tartar and plaque buildup of excess grains in processed foods and foods that dogs do not have to work at (chew) in order to swallow.
But, whatever you decide to do, just PLEASE do not give your dog a "Greenie" to help clean her teeth.