Have you tried Leba III spray? I used it on my older poodles and after about two weeks of spraying it in their mouth once a day, the existing tartar just fell off their teeth. You don't have to rub it on or anything , just spritz. Of course, I have heard that it does not help hidden tartar, but with my Standards, it really did help. Amazon has it for. about 42 dollars a bottle. I got it because a Papillon owner highly recommended it.