I see this often. A child has their permanent lower incisors coming out behind the baby teeth. We sometimes call it "Shark" teeth. The baby teeth have not come out like they were supposed to. It is most common with the lower front teeth when the child is six years old and now there are two rows of teeth. The good news is that the new permanent tooth will tend to move forward into the correct position and push forward on the baby teeth, usually causing them to fall out. Encourage your child to wiggle the baby teeth to get them to fall out faster. Consult with your Thornhill dental professional if the double row lasts for more than three months.