If a one-year-old baby’s teeth are dark, in most cases it is due to decay in the milk teeth. Because one-year-old babies eat a single diet, in most cases they eat dairy products and rarely show pigmentation. In the case of darkened adult teeth, it may be due to bad adult habits, such as tobacco and tea stains caused by smoking and drinking tea, resulting in exogenous darkening of the teeth. For one year old baby, most of the blackened teeth are caused by caries due to poor oral hygiene, and then decay and filling treatment is needed for caries as early as possible. If the decay of milk teeth is not intervened, it will soon diffuse the whole crown and lead to extensive decay of milk teeth and even cause the loss of milk teeth.