A few members give their pups antlers, by their posts the pups do well with them.
Have you tried ice cubes with treats frozen in the middle, plain ice cubes, frozen hand towels (big enough so pup can't swallow the towel), nylabones, kongs with frozen yogurt with treats in the middle for his chewing? You can also feed raw bones, i.e. chicken feet (great source of glucosamine), make sure raw bones are non-weight bearing bones, i.e. leg bones because they can break the pup's teeth. Some members give marrow bones but make sure they are big enough to not fit around the pup's muzzle as they can become stuck on their muzzle.