Black stains on teeth may be tooth decay, but there are many reasons for black stains on teeth, and whether it is tooth decay needs to be analyzed with the specific situation. Due to long time oral cleaning is not in place, resulting in various bacteria deposited on the surface of teeth to form tartar, this black stain is not tooth decay. Some people love to drink tea, coffee, cola and other dark-colored drinks, or take oral Chinese medicine, smoke, etc., and the pigment adheres to the surface of teeth, forming black stains, which is also not tooth decay. There is another kind of tooth decay caused by bacterial erosion, which is called tooth decay. This kind of black stain will destroy the integrity of teeth and make teeth soft. For the black stain on the teeth, you can choose ultrasonic shock to scaling to remove it, if the tooth reveals its original color, it is not a cavity. If the tooth is decayed, the black stain will need to be removed and then treated with a filling.