Tetracycline causes intrinsic tooth discoloration ONLY when administered during which period?

Correct answer: A. While the teeth are actively mineralizing (≈2nd trimester in utero through ~8 years of age)

• A. Correct. Tetracycline chelates calcium and is incorporated into mineralizing dentin/enamel and bone. It causes staining only during active tooth development — roughly the 2nd trimester in utero through ~8 years of age (when permanent crowns, e.g., the central incisors, are calcifying). Hence it is contraindicated in pregnancy and young children.
• B. Erupted, fully formed teeth do not take up tetracycline into their structure.
• C. After age 12 most crowns are complete; the risk window has passed.
• D. Adult teeth are fully mineralized and not affected.