The type of tooth that your dog loses determines whether another will grow in its place. The loss of an entire set of baby teeth is normal, but adult teeth falling out due to gum disease or trauma is not.
Deciduous and Permanent Teeth
Your dog will have two sets of teeth in his life: deciduous teeth as a puppy and permanent teeth as an adult. His deciduous teeth come in when he is around 3 weeks old and start falling out when he is about 3 months old. As the deciduous teeth fall out, permanent teeth erupt to replace them. This process usually happens from front to back, starting with the incisors and ending with the molars. Most dogs will have all of their permanent teeth by about 6 months of age. These permanent teeth are meant to last for life. If one falls out, it is not replaced by another tooth.