3-year-old baby teeth with black stains or gingivitis black line may be due to simple pigmentation caused by the baby did not have a thorough cleaning of the teeth caused by the parents should be careful to give the baby brushing, rinsing, teeth on the black pigmentation usually can not be removed by rinsing or brushing the teeth of the method of removal of the clean, if the child is very good with the degree of cooperation can be taken to the hospital to carry out ultrasonic scaling or polishing of the surface of the teeth and so on. A series of treatments. Baby teeth with black stains may also be the emergence of dental caries, its main symptoms are not only black pigmentation on the teeth, and tooth defects, cavities, the baby may appear tooth pain or stuffing pain symptoms, but also to take the baby to the hospital for caries treatment, to avoid the development of pulpitis or even periapical periodontitis caused by further infections and greater destruction of tissues.