The dentin is not as radiopaque as enamel. Which statement is true?

• A. Dentin is more radiopaque than enamel
• B. Dentin is less radiopaque than enamel
• C. Enamel is less radiopaque than dentin
• D. Dentin is invisible on radiographs

Answer: (B)

The concept being tested is how radiopacity differs between enamel and dentin. Enamel has the highest mineral content of any tooth tissue, about 96%, so it attenuates X-rays the most and appears very bright on radiographs. Dentin has a substantial mineral content but less than enamel, with more organic material and water, so it attenuates X-rays less and appears a lighter shade than enamel. Because of this difference in mineral density, dentin is less radiopaque than enamel. It’s not invisible on radiographs; it simply appears less white than enamel and more radiopaque than the pulp. Cementum, by the way, has even less mineral content than dentin and is typically less radiopaque than dentin.