Chapter 7 Midterm Questions

Question 1

What is enamel?

Answer 1

hard protective substance that covers the crown of the tooth, hardest biologic tissue in the body, consequently is able to resist fractures during stress of mastication

Question 2

What are Hunter-Schreger bands?

Answer 2

enamel rod configuration in incidental light appearing as light and dark bands of rod groups

Question 3

What is the percentage of inorganic material in the form of hydroxyapatite in enamel?

Answer 3

96%

Question 4

What is the percentage of water and organic matter in enamel?

Answer 4

4%

Question 5

What is hydroxyapatite

Answer 5

crystalline calcium phosphate that is also found in bone, dentin, and cementum

Question 6

What is the range of thickness of enamel?

Answer 6

knifelike edge at its cervical margin to about 2.5 mm maximum thickness over the occlusal incisal surface

Question 7

What is the function of each of the four enamel rods?

Answer 7

formed by 4 ameloblasts
one ameloblast forms rod head
a part of two ameloblasts forms the neck
tail is formed by a 4th ameloblast

Question 8

How wide is the head of the broadest part of the enamel rod?

Answer 8

5 micrometers wide

Question 9

How wide is the tail of the enamel rod?

Answer 9

1 micrometer wide

Question 10

How long is the enamel rod (both head and tail)

Answer 10

9 micrometers

Question 11

True or False

The rods that form enamel are woven during formation into a mass that resists average masticatory impact of 20 to 30 pounds per tooth

Answer 11

True

Question 12

True or False

The incremental lines in enamel are the result of the rhythmic recurrent deposition of the enamel

Answer 12

True

Question 13

Incremental lines may be accentuated due to?

Answer 13

variation in the mineral deposited at the point of enamel hesitation in deposition

Question 14

With enamel development, a row of ameloblasts covering the crown hesitates during deposition. The hesitation lines mark the path of what?

Answer 14

amelogenesis

Question 15

The hesitation lines, before called growth lines were termed _____ by Dr. Retzius?

Answer 15

striae of Retzius.

Question 16

A notable line if Retzius occurs at time of birth due to environment and nutrition change. What is this line called?

Answer 16

neonatal line

Question 17

True or False

The enamel internal to this line of a different consistency from the external to it because it was formed before birth, and the external was formed after birth

Answer 17

true (prenatal enamel has fewer defects than postnatal)

Question 18

True or False

The enamel formed before birth is less pigmented and has fewer defects than post natal enamel

Answer 18

True

Question 19

What are dead tracts?

Answer 19

tubules filled with air, hence they appear black in transmitted light

Question 20

What are enamel lamellae

Answer 20

cracks in the surface of enamel that are visible to the naked eye

Question 21

True or False

Lamellae are a possible avenue for dental caries

Answer 21

True

Question 22

True or False

Lamellae are not tubular defects but appear leaflike; extending around the crown

Answer 22

True