I've always given things like carrots, as you do, and brushed some of my dogs' teeth, but only in the last 20 or so years.
I don't really know what's helped, but all but one dog had great teeth. Pepsi the JRT, who we didn't get until he was 8, had terrible teeth.
But, I've got a pup again, and want to see if dental chews, or a particular brand of toothpaste might be something for him.
Obviously Charlie's getting the correct amount of food, or else his weight wouldn't be as good as it is. Good work.
Love All Life, Thank You For Posting! :)