If you brush your teeth every day and still have yellow teeth, there are two reasons for this. First, the color of the teeth itself is yellow. In addition to congenital factors, the color of the teeth itself is also directly related to age-related changes, and the older you are, the more yellow your teeth are. If your teeth are naturally yellow or yellow due to age-related changes, brushing your teeth will not alleviate the problem. If you want to whiten your teeth, you need to treat them by teeth whitening, including cold light whitening and restorative methods. Secondly, it is possible that there is a lot of calculus on the surface of the teeth, as well as tobacco stains and discoloration. Brushing alone cannot remove these substances, so you can consider treatment by scaling or sandblasting.