Most often, children loose their baby teeth naturally as permanent teeth start sprouting into their position. Occasionally, baby teeth may still be in position when a permanent tooth is trying to erupt into the same space. In these cases baby teeth may require extraction to make space for the permanent tooth to come in straight.
A very common example of over-retained primary teeth are “shark teeth” which is when lower permanent teeth start to grow in behind his or her baby teeth. The nickname comes from the fact that sharks also have a double row of teeth. “Shark teeth” are not an emergency and often don’t require any treatment. If the baby teeth do not loosen over a period of several months, bring your child in for an evaluation.