Usually, the first two teeth to erupt are the two bottom front teeth. Next, the top four front teeth emerge. After that, other teeth slowly begin to fill in, usually in pairs one each side of the upper or lower jaw, until all 20 teeth have come in by the time the child is 2 ½ to 3 years old. The complete set of primary teeth is in the mouth from the age of 2 ½ to 3 years of age to 6 to 7 years of age.

Between the ages of 6 and 12, a mixture of both primary teeth and permanent teeth reside in the mouth.