How old is this puppy?

Our question this week was:

We found a puppy but don't know how old he is. How can I tell?

The answer lies in the mouths of these babes. Puppies, like human babies, are born without teeth. Only the gum surface is visible. This allows them to nurse without hurting the mother. When they reach 30 days of age, their deciduous or temporary (baby) teeth start to break through the gums. This is referred to as "erupting." Puppies have a total of 28 deciduous teeth by the time they reach 45 days of age. This is a good time to give puppies plenty of chew toys.

As time goes by, these teeth are replaced by permanent teeth. The canine tooth fairy works somewhat faster than her human counterpart – most breeds show permanent teeth at 6 to 7 months of age.