I definitely notice a difference and I don't give them that often either. First they are very expensive and second my one dog has been caught swallowing hers whole. I used to use the Jumbo size but that seemed to make her chew it faster and swallow big chunks, plus if the other one still had hers they become "trophies" and its the only thing that will cause them to snap at each other. I refuse to have a dog fight between two 65lb pits over a greenie! So I switched them to, I think, the medium size ones and my one chews hers and they are gone quicker. But after that ramble to answer your question yes they definitely help to freshen breath.