Which of the following is an example of an endogenous tooth stain?

• A. Tetracycline staining
• B. Coffee stain
• C. Tea stain
• D. Red wine stain

Answer: (A)

Endogenous stains are intrinsic discolorations that come from within the tooth structure, usually during development, making them resistant to surface cleaning. Tetracycline staining is a classic example because tetracycline antibiotics can become incorporated into the enamel and dentin while teeth are forming (in utero or early childhood). The color change is inside the tooth and can appear yellow, brown, or gray with possible banding corresponding to developmental stages; since the pigment is internal, routine brushing won’t remove it and cosmetic treatments like whitening or veneers are often needed.

In contrast, stains from coffee, tea, and red wine are surface stains. They come from pigments that adhere to the outer enamel (extrinsic stains) and are generally removable with cleaning or whitening.