Most puppies begin to lose their deciduous (baby) teeth at around 12 weeks of age, although there can be quite a bit of normal variation. In general, small breeds tend to begin losing teeth later than large breeds.Teeth are usually lost front to back, starting with the incisors and ending with the pre-molars.his makes room for the permanent teeth to erupt normally. As with the deciduous teeth, the permanent incisors are the first to come in, followed by the canine teeth, and the premolars. The last teeth to erupt in the adult set are the molars. Puppies do not have molars, which is why there are fewer deciduous teeth.