Molly is still pretty young isn't she? I don't think it should be necessary for her to go to the vet to have her teeth cleaned.
Maybe you could get her some nice chew bones. I give my dogs raw marrow bones once a week or so and it really helps to keep their teeth clean. If you want to try that route just go to the butcher and ask for a couple of nice big marrow bones. You can ask the butcher to trim all the excess emat and fat off, or you can do it yourself. Scoop out the marrow (as it can be too rich for some dog's tummies) and give it to the dogs (outside preferably as they can get quite messy) and they will chew them for a long time.

The trouble with just scaling the teeth is that it scrapes away at the enamel of the tooth, making the tooth more suceptible to staining. At the vet they use special polishing stuff after they've scraped.