Enamel & Dentin Microstructure

Q: Dentinal tubules are classically described as:

S-shaped. Dentinal tubules follow an S-shaped (primary curvature) course.

Q: The smear layer is removed by:

EDTA. EDTA chelates and removes the inorganic smear layer.

Q: The neonatal line represents:

Birth stress in mineralising teeth. It is an accentuated incremental line marking birth.

⭐ High-Yield Facts for Exam

Enamel ~96% inorganic; dentin ~70%.
Enamel rods/prisms = keyhole shape.
Dentinal tubules = S-shaped.
Smear layer removed by EDTA.
Neonatal line = birth stress marker.

Enamel

~96% inorganic (hydroxyapatite). Structural features: enamel rods/prisms (keyhole), striae of Retzius (incremental), Hunter-Schreger bands, perikymata, and a neonatal line marking the birth stress in teeth mineralising at birth.

Dentin

~70% inorganic; permeated by S-shaped dentinal tubules housing odontoblast processes; types include primary, secondary, and tertiary (reactionary/reparative) dentin. The smear layer is grinding debris removed by EDTA before bonding.

Exam Tips ⭐

Enamel ~96% inorganic; dentinal tubules are S-shaped; smear layer removed by EDTA; neonatal line = birth marker.

📝 Practice MCQs — Enamel & Dentin Microstructure

Q1. Dentinal tubules are classically described as:

A. Straight

B. S-shaped

C. Circular

D. Branched only

Show Answer

✅ Answer: B

Dentinal tubules follow an S-shaped (primary curvature) course.

Q2. The smear layer is removed by:

A. NaOCl

B. EDTA

C. Saline

D. Water

Show Answer

✅ Answer: B

EDTA chelates and removes the inorganic smear layer.

Q3. The neonatal line represents:

A. Caries

B. Birth stress in mineralising teeth

C. Fluorosis

D. Attrition

Show Answer

✅ Answer: B

It is an accentuated incremental line marking birth.

📧 Get Free NEET MDS MCQs in Your Inbox

50 high-yield MCQs + mnemonics + AI study tips — completely free

No spam. Unsubscribe anytime.

⭐ High-Yield Facts for Exam