Do you have chew-happy dogs?
To make them happy and keep their teeth nice and clean, get beef soup bones from the butcher and roast them for about 20 minutes on a foil-lined sheet pan in a 350 degree oven. It kills bacteria on the outside and renders off a lot of the fat.
After cooling entirely, freeze them in zip-lock bags and dole them out when you have to leave your dog alone. They end up licked-clean.
Another idea is to get a long hollow bone and put peanut butter inside. Freeze it. Your dog will be busy for hours!