The blackening of the tooth crevices may be the effect of pigmentation. People who love tea and smoking do not clean them in time, which can leave these tea and smoke stains or be stained by other food medications. If it is these reasons, the problem is not big, you can use ultrasonic teeth cleaning and polishing to remove it, but after removing it, you must brush your teeth carefully and change your living habits to be able to keep it. There is also a cause of tooth decay, and tooth decay should be treated in time once it is found. If the cavity is small and the tooth nerve is not hurt, it is only necessary to grind away the decayed part to fill the tooth. No matter what the reason is, the blackening of the tooth is a kind of reminder. It means that the oral hygiene is not very good and should be improved to prevent the problem before it happens.