I use Oxyfresh, tried Oxydent and didn't help. Plaque Off is a powder additive, used it for ages; I'm having better luck with Finn. Dogs always had chewies, loved Bully Sticks... stopped them and now have a large variety of Dental Chews around instead. I truly believe dental issues are a mix of genetics and food and gee, maybe even what's in the water.
Have you considered a sonic tooth cleaner? If she is willing, I have great luck with one. There is an awesome organic toothpaste... Black Sheep Organics... my dogs love it! When you receive the container after paying the price you might be like.. what???? But it is VERY effective and lasts forever. I personally believe with dogs and teeth, you really have to try and see what works for your dog.
Does Willow need a dental? Who knows... Might be your vet looking at her age and suggesting because of that... might be something going on with her gums or teeth, might be they want work - who knows... I'd ask your vet exactly why they are recommending. I stewed over a dental for Brodie - he and Willow are same age - and last year she mentioned Brodie's teeth showed plaque. A year later, I had almost convinced myself I'd okay a dental, and she said his teeth looked great - Deacon's were a concern. I figure sooner or later I will probably do one, he turns 8 in November, feel I want to at least do it before the double digits arrive.
Such a hard decision. I hope you keep posting on what you do and why...