question: I have been brushing and flossing my son's teeth since he was one year's old. He is 17 months now. I recently noticed that on his two bottom teeth he has a dark line around two of his bottom teeth. Its not directly by the lining of the teeth but under the pink lining like a stripe circumferencing the two teeth. He has an appointment on March 21. Should I be concerned and see if the doctor can see him right away?