Dogs typically start losing their baby teeth when they are around 3 to 4 months old. This teething period continues until about 6 to 8 months of age, by which time all their baby teeth have usually fallen out and been replaced by adult teeth. The first teeth to fall out are usually the incisors, followed by the canines and then the premolars. It's normal for puppies to lose their baby teeth gradually, and sometimes the teeth are swallowed and not found. By around 6 to 8 months, puppies usually have a full set of 42 adult teeth.