Enamel is much harder than dentin, but it is

• A. More ductile
• B. Less dense
• C. Softer
• D. More brittle

Answer: (D)

Hardness and brittleness aren’t the same thing. Enamel is extremely hard and stiff because it’s highly mineralized, but that same crystalline, collagen-free structure gives it low fracture toughness. In practical terms, enamel can resist indentation strongly, but it doesn’t deform plastically before cracking. When stressed, cracks propagate quickly through enamel, making it brittle.

Dentin, on the other hand, has organic matrix (collagen) and water, plus a tubular structure that helps deflect cracks and absorb energy. This makes dentin tougher—even though it’s softer than enamel—so it resists crack growth better than enamel.

Enamel is denser than dentin due to its high mineral content, not less dense. So the best description of enamel’s behavior is that it is more brittle.