The child appeared six years old fossa closed after the black line, the main reason is because the oral hygiene cleaning is not in place, no effective cleaning and brushing reasons for the formation of the root cause is the bacterial destruction of the teeth lead to black, there may also be pigmentation. 1. This situation should pay attention to in life to master the correct method of brushing, try to take the upper and lower brushing method, you can also use the electric toothbrush, electric toothbrush than ordinary toothbrush cleaning rate to be a little higher, can be effective in the depth of the teeth of the food residues and bacteria effectively get rid of, and develop a good health habits. 2. Rinse your mouth with warm water or mouthwash every time you finish eating, which can effectively protect your teeth. Bacterial destruction of teeth blackened, it is best to take the child to the regular hospital to do an oral examination, you can take the filling approach or dental restoration approach to targeted treatment. In order to prevent the aggravation of the child’s teeth lead to the emergence of pulpitis and other symptoms, daily life should pay attention to reduce the consumption of snacks, especially candy chocolate and other sweets. If there is any abnormality, consult a doctor for timely examination and treatment.