Enamel Structure and Biomechanical Properties

Question 1

What is the enamel thickness of incisors?

Answer 1

0 to 2mm

Question 2

What is the enamel thickness of molars?

Answer 2

0 to 2.6mm

Question 3

What is the refractive index of enamel?

Answer 3

1.655

Question 4

Comment on the solubility of enamel

Answer 4

Soluble in acids

Question 5

What is Mucopolysaccharidosis?

Answer 5

• Genetic abnormality
• Doesn’t allow enamel and dentine to bond at EDJ
• So could potentially cause cracks in enamel

Question 6

Describe the crystallite orientation throughout the enamel

Answer 6

• All the crystals are in different directions

- Perpendicular from the EDJ

Question 7

On the Moh scale what is the hardness of enamel?

Answer 7

5 to 8

Question 8

What is the compressive strength of enamel?

Answer 8

350 MPa

Question 9

What is the shear strength of enamel?

Answer 9

90 MPa

Question 10

What is the tensile strength of enamel?

Answer 10

10 MPa

Question 11

What is the maximum biting force administered to the teeth?

Answer 11

640 N

Question 12

What is the maximum stress administered to the teeth?

Answer 12

20 MPa

Question 13

What is the elastic modulus of enamel?

Answer 13

50GPa to 100GPa

Question 14

Compare the elastic modulus of cross sectional enamel to surface enamel

Answer 14

Cross-sectional enamel has a lower elastic modulus than surface enamel

Question 15

What does high fracture toughness show?

Answer 15

High fracture toughness shows improved clinical performance and reliability.

Question 16

Comment on the structural integrity of enamel when there is crack propagation and subsequent fracture

Answer 16

Crack propagation and subsequent fracture leads to ultimate structural failure.

Question 17

What is the enamel microstructure made of?

How does this help its function

Answer 17

Nano-scale HAP crystallites

High strength

Question 18

Why is the thickness of crystallites 30nm?

Answer 18

This thickness is optimum for stress resistance