I understand what you are saying about the Greyhounds, because my niece adopted a Greyhound with very bad teeth and they told her the same exact thing! I have Kalina on the raw diet and her teeth look pretty and her breath is pleasant. I give her the medallions but I also give her a RMB to chew on a few times a week. She never finishes the bone, but she enjoys them and so I have decided to continue giving them to her.
I hear that fresh green tripe is absolutely fantastic for the teeth - something to do with the Ph balance. I give Kalina a little bit of green tripe every day. She loves it. Here is an interesting article about green tripe.
http://www.fleetfiretimbers.com/FFT/...utsNoGlory.htm