Physical Characteristics

Question 1

What forms a protective covering over the surface of the crown?

Answer 1

Enamel

Enamel has variable thickness, reaching up to 2-2.5 mm on the cusps of molars and premolars.

Question 2

Where is enamel found to be thicker in the human molars?

Answer 2

Lingual surfaces of maxillary molars and buccal surfaces of mandibular molars

The increased thickness in these areas may be an adaptation to functional demands.

Question 3

What is the hardest calcified tissue in the human body?

Answer 3

Enamel

Enamel’s high content of mineral salts and crystalline arrangement contribute to its hardness.

Question 4

What is one of the main functions of enamel?

Answer 4

To form a resistant covering of the teeth for mastication

Enamel’s structure and hardness make it brittle, especially when losing its foundation of sound dentin.

Question 5

How does the modulus of elasticity of enamel change?

Answer 5

Higher at the surface than at the dentinoenamel junction

This leads to variations in mechanical behavior in different areas of the enamel.

Question 6

What is the specific gravity of enamel?

Answer 6

2.8

The density of enamel decreases from the surface to the deeper regions.

Question 7

Is enamel electrical conductive or insulating?

Answer 7

Insulating

Enamel is a nonelectrical conductive material and acts as an insulator at room temperature.

Question 8

What is the range of electrical resistance of enamel?

Answer 8

From 10^15 to 10^9 ohms

This measurement indicates the high resistance properties of enamel.

Question 9

What color is enamel typically described as?

Answer 9

Yellowish white

The color of enamel can be influenced by various factors including translucency and dentin beneath.

Question 10

What are the main organic components found in enamel?

Answer 10

Amelogenins and tuftelin

These organic materials account for only a small amount of the overall enamel composition.

Question 11

What amino acids are commonly found in enamel proteins?

Answer 11

Hydrophobic amino acids and leucine

These contribute to the structural integrity of enamel.

Question 12

Fill in the blank: The thickness of enamel decreases from the _______ to the deeper regions.

Answer 12

surface

This change in thickness impacts the mechanical properties of enamel.

Question 13

True or False: Enamel is a good conductor of electricity.

Answer 13

False

Enamel is an insulator and shows nonelectrical conductivity.

Question 14

What is the primary composition of enamel?

Answer 14

Enamel consists mainly of inorganic material (96%) and only a small amount of organic substance and water (4%)

The organic material includes some unique proteins.

Question 15

What property of enamel allows it to act like a semipermeable membrane?

Answer 15

Enamel’s permeability permits complete or partial passage of certain molecules

This has been demonstrated using radioactive tracers and dyes.

Question 16

How does the translucency of enamel affect the color of teeth?

Answer 16

Yellowish teeth have thin, translucent enamel allowing the yellow of the dentin to show, while grayish teeth have more opaque enamel

Translucency variations are attributed to the degree of calcification and homogeneity of enamel.

Question 17

What color range can enamel-covered crowns exhibit?

Answer 17

Enamel-covered crowns can range from yellowish white to grayish white

The color is influenced by the translucency of the enamel.

Question 18

What phenomenon occurs at the cervical areas of grayish teeth?

Answer 18

Grayish teeth frequently show a slightly yellowish color at the cervical areas

This is due to the thinness of the enamel allowing light to strike the underlying yellow dentin.

Question 19

What effect does dehydration have on the translucency of enamel?

Answer 19

Dehydration decreases the translucency of enamel

This decrease is reversed upon rehydration.

Question 20

What is the transmission coefficient of enamel at 525 nm?

Answer 20

The transmission coefficient at 525 nm is 0.481 mm

This coefficient indicates how much light can pass through the enamel.

Question 21

Fill in the blank: The enamel has been found to permit the passage of _______ labeled urea.

Answer 21

14C