Which of the following is NOT an endogenous stain?

• A. Tetracycline staining
• B. Fluorosis
• C. Non-vital tooth discoloration
• D. Coffee stain

Answer: (D)

Endogenous stains come from inside the tooth, usually during formation or due to internal changes, whereas exogenous stains come from outside the tooth after eruption. Tetracycline staining results from antibiotic exposure during tooth development, fluorosis from excessive fluoride intake during enamel formation, and non-vital tooth discoloration occurs from internal changes after the pulp dies. Coffee stain is external in origin—the pigments in coffee deposit on the enamel surface after eruption—so it’s considered not endogenous. This type of stain is typically removable with cleaning or whitening since it starts on the outer surface rather than inside the tooth.