I am also intrigued by the idea of using this product in the water applied to the dogs' food - it would solve the waste and expense problem of frequent water changes. We see the dental specialist on Jan 4 and I will ask her her opinion about efficacy when used that way. My guess is that it is most effective when used away from food, as a sort of ad hoc rinse, but it would be really great if it also worked in food.
FWIW, in addition to brushing their teeth after breakfast every morning, I add Wysong's Dentatreat to their food in the evening. It really helps with breathe and the yellow staining Arlie is prone to (of my three, she has the worst teeth). Dentatreat can also be used mixed with a little water as a toothpaste and works well and is cheaper that way, but I found brushing teeth twice a day was too much for me.