Some of the causes of black teeth are foods and drinks, tobacco use, poor dental hygiene, diseases, medications and dental materials, according to MedicineNet. Genetics and excessive fluoride use are also possible factors.
Some foods and drinks stain the teeth, says MedicineNet. These include coffee, tea, wine, cola and certain fruits and vegetables, such as apples and potatoes. Smoking or chewing tobacco also tends to darken the teeth. Proper brushing and flossing are important to get rid of plaque and substances that produce stains from coffee and tobacco as poor dental hygiene causes tooth discoloration.
Moreover, some diseases affect the enamel and dentin, leading to darker teeth. The enamel is the hard surface of the teeth, while the dentin is the material under it. Certain medications, such as the antibiotics doxycycline and tetracycline, darken teeth when taken by children below 8 years of age. Furthermore, amalgam restorations and materials containing silver sulfide, which are used in dentistry, can give the teeth a gray-black color.
MedicineNet notes that genetics is a possible reason for dark teeth as some people naturally have thicker or brighter enamel than others. Excessive use of fluoride, either from water or from fluoride applications and supplements, can also lead to discoloration of teeth.