Enamel Rod Morphology — NDEB AFK MCQ
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Correct answer: E — Keyhole (or fish-scale) shape
Enamel rods (prisms) have a characteristic keyhole or fish-scale cross-sectional shape when viewed in scanning electron microscopy. The head (wider portion) contains tightly packed hydroxyapatite crystals oriented parallel to the rod long axis, while the tail (narrower portion) has crystals oriented at an angle. The inter-rod enamel has crystals oriented perpendicular to the rod direction. This organisation creates the enamel prism pattern that is exploited by acid etching for adhesive bonding.
Reference: Nanci – Ten Cate's Oral Histology, 9th ed., 2017