Nicotine can quickly cause yellowing of your teeth. This occurs whether you smoke cigarettes or use chewing tobacco. Nicotine and tar settle into the very small cracks in the enamel of your teeth, and cause discoloration. It has been shown that nicotine helps the process of plaque formation, which leads to a faster deposit of tartar and can cause bad breath. In addition to discoloration, nicotine use can cause other physical problems for your teeth and gums. You may be prone to increased cavities, gum disease, and certain types of oral cancer. All of these ailments can decrease the healthy appearance of your teeth. One way to prevent the yellowing of teeth is to make sure that you are taking excellent care of your mouth. Good oral hygiene includes brushing your teeth twice a day. You should use a whitening toothpaste in combination with a soft-bristled tooth brush. Brush firmly but gently at least twice a day. Flossing is also important. You should make sure to use dental floss once a day. This can remove buildup of foreign material between your teeth. The best way to put a stop to the yellowing of your teeth is to quit using nicotine. Quitting is a very difficult process, but there are many methods you can try. Consider using cessation aids, such as chewing gum or nicotine patches. There are also prescription medications to help with your addition. Ask your doctor for help in choosing a safe and effective method.

TL;DR in Chinese:
了解牙齿变色的原理。 了解患病风险。 注意口腔卫生。 尝试戒烟。