Tooth decay remains one of the most common childhood diseases, but you can help save your child’s pearly whites by following these tips from Jill DeBiasi, DDS, mother of three and co-owner of DT Smile Design in New York City. Go electric. Choose an electric toothbrush over a manual one; the vibration eases the bristles under the gums, an area most kids miss. Use fluoride. Buy fluoride toothpaste when your child is 2 or older. It recalcifies teeth and can help prevent cavities. Time it. Make sure your child brushes for two minutes—30 seconds per quadrant. Make it fun. Have him watch you as you brush your teeth together. Mimicking your good habits will help him start his own.