What is the reason for the black on the teeth of an 8-year-old child after losing a tooth?

Patient's question:

No

Doctor's answer:

Hello, it is recommended to first check whether the lead, mercury, and other toxic substances in the child's blood and urine are above the standard. If the above suspected factors are ruled out, it is suggested to remind the child to brush their teeth in the morning and evening, rinse their mouth after meals, and pay attention to oral hygiene.