A number of factors can cause black spot on teeth. Teeth that turn black are usually due to one of two common types of causes :- Extrinsic or Intrinsic. #Extrinsic: Extrinsic damage comes from the outside of the teeth. This includes staining, tartar, or other damage that affects the outer dental enamel. #Intrinsic: Intrinsic damage starts on the inside and progresses outward. This occurs when a condition within the tooth causes decay and damage. A tooth will not turn black overnight, instead, it will happen over time. It is best to see a dentist before the damage becomes too great. Some common causes of black teeth include: #Cavities: Cavities are caused by bacteria that destroy dental enamel, leaving small holes behind. These holes can take on a dark appearance. #Dental restoration. Fillings and crowns that contain amalgam, particularly silver sulfide, can cause teeth to appear black in color. #Staining. Eating and drinking dark-colored food products, such as tea and coffee, can stain teeth. #Taking certain medications. Liquid iron supplements, for example, can lead to staining of the teeth. #Tartar. Tartar is a hard deposit of plaque that can build up on the teeth and usually appears below the gum line. Some forms of tartar are black. #Tobacco. Smoking or chewing tobacco can significantly stain the teeth. Most underlying causes of black teeth require a dentist’s care to remove or treat