Deciduous Teeth (teeth that are shed) are a child’s first set of teeth. They are also known Milk Teeth, Baby Teeth, Temporary Teeth, and Primary Teeth. Deciduous teeth develop in the womb, and erupt (become visible in the mouth) during the first three or four years of life. As childhood progresses, they are are gradually lost and replaced by Permanent Teeth. The illustration above shows the usual ages at which a child’s Deciduous Teeth are replaced by their Permanent Teeth.