do you give him anything to help clean his mouth? raw bones? dental treats { although im still not convinced those work all that well}, also you could brush his teeth a few times a week to help as well. try adding some Apple cider vinegar to the water as well , like a small capful or half a capful. I started adding it for a different reason { it has good benefits for many things} and noticed the one girl I have with bad breathe it improved a bit. Only thing I had changed was the ACV so im accrediting it to that LOL.