When your baby is about 4-7 months in age, then their primary teeth (also known as baby teeth) first start to erupt. This process usually begins with the teeth in the front of their mouth. The primary teeth help your child to eat, speak, and smile until their jaws are large enough to hold permanent teeth. When your child is about 6-7 years in age, their baby teeth will begin falling out, after which they are replaced with adult teeth.