Just a note on a different source of the bad breath. When Reggie was little, he had horrible breath. I told the vet about it when I took him in to get neutered so he could clean and check his teeth. He found a bit of carpet or plush toy that had wound around a very back tooth and wasn't visable when looking in his mouth. Needless to say, it had gotten pretty rotten and was where the horrible "odor" was coming from. The vet said that puppies chew so much that sometimes that happens. He'd never seen such a nasty one tho.
So sometimes bad breath has a real source too.