The causes of blackened teeth of patients are mainly long-term consumption of pigmented food and dental caries, as follows: 1. Long-term consumption of pigmented food: long-term consumption of pigmented food, such as long-term consumption of strong tea, coffee, etc., will form pigmentation on the surface of teeth, which will lead to blackened teeth, only need to visit the hospital for full mouth cleaning to remove the pigmentation on the surface of teeth. 2. Dental caries: Tooth decay will cause the tooth to become black, is the tooth decay, commonly known as tooth decay, mainly due to bacterial infection, bacterial acid production, resulting in the demineralization of the hard tissue of the tooth, organic matter decomposition, resulting in the loss of the hard tissue of the tooth, resulting in the blackening of the surface of the tooth and the formation of cavities. There are four main causes of tooth decay, which are bacteria, environment in the mouth, host and time. If we reduce the intake of sucrose in food, reduce the frequency of eating, protect the mouth, keep the mouth clean, remove the local stimulus and brush the teeth on time, the possibility of tooth decay will be greatly reduced.