Dogs' teeth fall out when puppy teeth, called "milk teeth," are replaced by permanent ones. Most puppies, like human babies, are born without teeth, but they begin to cut their first teeth when they are two or three weeks old.
All of the baby teeth are usually out by the time the puppy reaches six to eight weeks of age, just in time for the first permanent teeth to begin to appear. The first teeth fall out as the permanent ones come in, but the permanent teeth outnumber the baby teeth by 14. When an owner takes proper care of a dog's teeth, they usually last for most of the dog's life, but older dogs often lose some of their teeth. The dog's incisors, the teeth at the front of the mouth, are usually the most likely to fall out first.