Like humans, dogs have two sets of teeth in their lives. The 28 baby teeth erupt through the gums between the third and sixth weeks of age. Puppies do not have to grind much food, so they do not have molars. Puppy teeth begin to shed and be replaced by permanent adult teeth at about four months of age. Although there is some variation in breeds, most adult dogs have 42 teeth, with the molars coming last, at about six or seven months.
The order of tooth replacement is incisors first, then canines (fangs), and finally premolars. The teething period can be frustrating; the puppy clamps his mouth on everything he can reach, from body parts to Johnny's $80 sneakers, in an attempt to relieve the discomfort. Teething can be accompanied by drooling, irritability, and fluctuations in appetite.