The reasons for baby teeth darkening are as follows: 1.If oral hygiene cleaning cannot be strengthened, and the teeth cannot be brushed and rinsed in time after meals, the melanin in food and drinks will be deposited on the surface of the milk teeth, making the tooth surface dark. 2.When babies like to sleep with milk bottles, a large amount of food residues and soft scales adhere to the surface of milk teeth, resulting in extensive caries and blackening of milk teeth. 3.After the milk teeth are impacted by external forces, periodontal shock occurs, causing the tooth pulp to become dark. 4.Frequently gnawing on hard food, causing the tooth tissue to crumble and the tooth color to become dark after the chronic necrosis of the tooth pulp. 5.When applying Chinese medicine, it can cause the tooth surface and mucous membrane to be colored, resulting in the phenomenon of blackened teeth.