I find the dog toothpaste that is mint works better to control bad breath then the flavored kind. Also, try some freshener to spray after brushing. Koi's food gives him horrible bad breath and his teeth are squeaky clean. There is also a thing...I can't remember the name but we sell it at PetSmart. It's a foam bone-like thing that you can fill with a paste. They chew on it and it cleans their teeth/freshens breath at the same time.
The reason I don't recommend Dingos is because they still get soggy and can impact intestines if swallowed. My boss lost her Saint Bernard to that
Greenies aren't gummy, they tend to crumble more than anything else. I've had no problems with them.