Stain formed inside the tooth structure from inside sources.

The answer to this question: Satins formed inside the tooth structure from INSIDE sources, would be: intrinsic staining.

Explanation:

When talking about tooth appearance and tooth health, people tend to see stains on teeth and wonder if the problem is a lack of hyginie from the person who has them, or if there might be a different reason. While indeed there are stains that are caused on the tooth due to bad nutritional habits, and bad hyginie, there are others, known as intrinsic staining, that happen due to causes that are beyond a person´s control. Intrinsic staining is defined as the stains that appear on the inside structure of a tooth, they are caused by problems in the formation of the tooth, and they cannot be removed by professionals, or by anything. It is almost like they are part of the tooth itself. Exposure to certain elements, such as antibiotics during teeth formation, can result in intrinsic staining.

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