I haven't yet taken our daughter in to the dentist for this, but... She has yellow spots on the front of both of her front teeth. The pediatrician said it is from the antibiotics she was on while those teeth were developing. Not all kids get it, but some (mine) do. I haven't checked the backs. Is he certain it is carries/cavities/whatever? She just called it stains and some weakened enamel and to be careful to brush often.