I am a little late to this, but I wanted to also mention Plaque Off, which we've been using for our pooch after her teeth started yellowing a bit... http://www.amazon.co.uk/PlaqueOff-60g/dp/B001A323C4
I just sprinkle it on her food and she doesn't mind at all. The problem came when my (now ex) boyfriend started giving her loads of chicken and other meaty treats, and she pretty much went off the kibble, veggies and carrot chews, etc, I used to give her. She used to love chewing raw carrots straight from the fridge and that seemed to do a good job of keeping her teeth clean, but now she's on Benevo wet food as she's been so spoiled it's pretty much all she'll eat. I definitely noticed a difference in her teeth since she stopped being interested in the kibble.