A dog's ability to control the force of his biting is called "bite inhibition." It's a critically important skill that every puppy needs to learn, the earlier the better. At first, they don't know their own strength nor how sharp their little teeth really are. Puppies learn to control the force of their biting from the reactions of their mothers and littermates during play and especially play-fighting.
We can teach puppies about bite inhibition, too, but some of the methods most often recommended aren't effective. Mother dogs' methods, however, are very effective, often more so than ours. I believe this is because they're speaking to their pups in the language they understand best -- dog language! A baby puppy is much too busy learning how to be a dog to take time to understand our human words and ways. That takes time and maturity. Puppies respond to dog language in a very powerful, instinctive way. We can take advantage of that by copying a mother dog's actions and using them for ourselves.
The idea of using mother dog's natural training techniques isn't new. Respected trainers like Carol Lea Benjamin have been using them for years. To understand these methods, let's take a look at a typical mother dog disciplining her brood. We'll use my Heather (Chow) and her four rowdy puppies as an example.
When a playful puppy bites Heather hard enough to hurt, she squeals in shocked indignation. The puppy, surprised at her reaction, usually hesitates a moment, unsure of himself, then tries to bite again. Heather yelps even louder this time and whirls on the puppy, growling, showing her teeth and scowling at him fiercely. Then she turns her back on him and storms away, completely ignoring him and any further attempts to get her to play. A smart puppy picks up her clear message quickly: "if you can't play nice, I won't play with you at all!"
If the puppy persists or doesn't take the hint, Heather doesn't fool around. With a menacing growl and using her teeth, she grabs him by the scruff of his neck and gives him a shake. If he sasses back, she gives him another little shake, tougher this time. She doesn't let go of the pup till he's acknowledged her authority (in dog language) by relaxing his body, laying his ears back and keeping still for a moment. Heather disciplines especially obnoxious puppies by knocking them over with her paw and pinning them to the ground, growling angrily and pinching them with her teeth. The puppies shriek but they're not really hurt. She doesn't let them up again untill they relax and lie still.