Summary from Peteducation:
http://peteducation.com/article.cfm?c=2+2089&aid=874A few facts and tips about keeping your dog's teeth healthy.
-By the age of 4, 70% of dogs start showing signs of some sort of dental problem (e.g. gum disease)
-Good dental hygiene is important in preventing these problems.
You can do the following to keep your dog's teeth healthy:
-Dry kibble helps some, while it doesn't remove plaque 100% it doesn't contribute to it as much as soft foods would
-Give your dog a nylon bone or some other chew toy to help scrape some of the tartar off.
-Brush a couple times a week using tartar control toothpaste.
-Make sure that folds of skin around the mouth are clear of food using dental cleansers
-In cases where tartar build-up is serious, the teeth may need to be scaled and polished. You can do this yourself or have your vet do it.