If you find that the color of the teeth become black, there are three reasons can be caused. 1, pulp necrosis, when the pulp necrosis of the teeth root canal will form more bacteria, and the teeth lose blood vessels and nerves of the nourishment become more brittle, this time the color of the hard tissue of the teeth will slowly darken dark; 2, the surface of the teeth caries can also make the teeth color black. Caries is caused by bacterial infection of dental hard tissue disease, tooth enamel will slowly become black, peeling, softening; 3, the surface of the teeth have black spots or dots, may be caused by hyperpigmentation. Often seen is smoking patients or often drink coffee, tea patients, teeth inside the mouth, especially on the side of the tongue there will be more smoke stains.