What causes the yellow-orange color of rodent incisors as the animal ages?

• A. Iron Deposits
• B. Calcium deposits
• C. Porphyrin buildup
• D. Melanin accumulation

Answer: (A)

In rodents, incisors keep growing throughout life, and iron from the oral environment becomes incorporated into the forming enamel and surrounding dentin as the tooth develops. This ferruginous (iron-containing) pigmentation accumulates with age, giving the incisors a yellow-orange color that is commonly seen in mature animals. It’s a normal pigment change tied to iron deposition in dental tissues, not a sign of disease.

Calcium deposits would typically alter mineral content and might appear white or chalky rather than orange. Melanin accumulation tends to darken teeth more broadly to brown or black, not specifically produce a yellow-orange hue. Porphyrin buildup can color teeth pinkish or reddish in some contexts, but the distinct aging-related orange tint seen in rodent incisors is best explained by iron deposition in the enamel.