Well, here's the follow-up on the dental spray I've tried on AJ.
As with good food, it only works if you can get it into the dog. AJ hates the spray and runs from me when I get the bottle out. I'm not sure whether it's the burst or it's the peppermint flavor, but he absolutely loathes the stuff.
I will say, though, that with the few times I've been able to get it onto his teeth, his breath has improved and his teeth are a little whiter. My verdict is this: I will give up torturing my dog with it, but if your dog tolerates it, it is effective.