I decided after checking out all the other possibilities of tooth decay, and anal glands ( I know- eww) that I was going to switch him to a Raw Meaty Bones diet and I did. I can not tell you in the month that he has been on it how much better his breath is overall. That's only one benefit to the diet. He gets plenty of roughage with this diet and it is very efficient in his body so it reduces the overall volume of feces he produces everyday (Just less poop is a 5 star benefit). He also has to strain more to do his business so it helps to really flush out his anal glands on their own. No more expressing them hopefully!
He is energetic but not as hyper as he was. There are variations like the BARF diet (Bones and Raw Food) but many do not believe that dogs are omnivores so they should not be given raw vegetables or fruits. The RMB diet is feed in proportion of 80% meat-10% bones and 10% offals (innards like kidneys etc)
It might sound time consuming and complicated but it's not. I buy the meat from the grocery store and portion it out based on his weight which is 3-4% of his total weight. I can freeze it and thaw it out to give to him at dinner time.
The biggest problem I have had so far is that he likes to hide his dinner for late night snacking and I can usually find it by the smell, so I have had to have him eat dinner in his box with the door locked.
I have even switched my cats to the RMB diet and they are a little more reluctant but they are adapting to it fairly well.
Here is some good reference if you are thinking of the switch to a RMB diet:
*Editor's Note : Visit Shannon's Stylist Shop at stella & dot.