Which stain is considered endogenous?

Endogenous stains are those that develop from within the tooth structure, often due to systemic factors or internal processes. Tetracycline stain qualifies as an endogenous stain because it results from the incorporation of tetracycline antibiotics into developing teeth during the period of tooth formation. This incorporation leads to a discoloration that can manifest as a dark yellow or brown stain on the teeth.

To clarify, other types of stains listed in the options do not fit the criteria for endogenous stains. Yellow stains, while they may be present on the tooth surface, are typically caused by extrinsic factors like dietary choices or habits rather than systemic internal processes. Black line stain is also considered an extrinsic stain, commonly associated with certain dental biofilm deposits and reinforcement by dietary factors. Extrinsic stains arise from external sources, such as foods, drinks, and oral hygiene habits, and do not originate from within the tooth structure.