Teeth can change color for a number of reasons (we should not confuse that with slightly ”yellowing” which occurs with age). Teeth may turn brown due to smoking, while the dead teeth are completely gray. Some drugs, e.g. tetracycline, may disrupt the creation of tooth enamel if taken in high doses in childhood.
Heavy forms of some childhood infections, such as pertussis or measles, may also alter the color of the (part of the) tooth. Too much fluoride concentration in water, as found in some parts of Africa, can cause fluorosis – white or brown spots on the teeth. This, of course, does not occur in areas where the controlled amount of fluoride is added to the water to prevent tooth decay (caries).
If the decoloration is on the surface, the dentist will clean the tooth with a rotating polishing tool and a polishing paste. Deep decolorization is corrected by fixing the lining of a solid, white plastic to the tooth, or by placing the porcelain crown.