Teeth long black stains, there are several reasons: first, brush teeth not seriously, not thorough, did not achieve effective brushing, brushing should be used to professional whitening toothpaste for the upper and lower whisk brush, brush carefully, brush the surface of the teeth clean plaque, soft scale, the chances of long black stains will be much lower; second, the usual diet often use melanin-containing food, such as coffee, soy sauce, chocolate, etc., diet to increase food However, when brushing teeth is not effective as soon as possible, melanin deposition will be accelerated; third, the patient’s bad habits are not quit. For example, smoking, long-term smoking will lead to increased melanin deposition on the teeth.