Archie posted a thread on Buddy with "after" pictures, and considering he's four years old it's truly remarkable, yorkies are known for having problems with tartar. Here's the link.
http://www.yorkietalk.com/forums/my-...e-my-dear.html If your dog already has a tartar problem, it will probably take several months to see results, and you should also be brushing his teeth. Petzlife softens the tartar and brushing helps remove it.
I've been using it on Joey since he was a puppy, he's only 1 1/2 now, but the vet commented on how good his teeth looked.