Dogs' baby teeth begin to loosen and fall out by eight to 12 weeks of age. The process of replacing baby teeth with permanent teeth can continue until the dog is eight months old. Normally, a puppy has 28 baby teeth and an adult dog has 42 teeth.
There are three sets of teeth: incisors, canines and premolars. Puppies don't have premolars. Any baby teeth that don’t fall out to make way for the adult teeth are called retained or persistent deciduous teeth, and they can cause dental problems. A dog's teeth should be checked regularly to provide the best dental health.