Chapter 7

Question 1

What are hunter-schreger bands?

Answer 1

alternating dark and light bands in enamel that result in absorption and reflection of light caused by differences in orientation of adjacent groups of enamel rods originating at the DEJ and extending toward the outer enamel surface

Question 2

True or False

Enamel rods extend from their site of origin at the dentoenamel junction to the enamel outer surface

Answer 2

True (each rod is formed by our ameloblasts (one) forms the rod head: two form the neck and the tail is formed by a fourth ameloblast)

Question 3

Rods run almost perpendicular to the enamel surface at the _____ _____, but are enlarged and intertwined at the ____ _____

Answer 3

cervical region

cusp tip

Question 4

What factors challenge enamel

Answer 4

demineralization caused by caries
occlusal wear by attrition
fracture (brittleness)

Question 5

True or False

Rods form nearly perpendicular to the dento-enamel junction and curve slightly

Answer 5

True (toward the cusp tip this unique rod arrangement also undulates throughout the enamel surface. each rod interidigates with its neighbor, the head of one rod nestling against the necks of rod R & L).

Question 6

Where is the prism less enamel found?

Answer 6

cervical region of all teeth and also in deciduous teeth (no schreger band effect noted in these areas)

Question 7

True or False

When enamel has been completely formed no more enamel can be deposited.

Answer 7

True

Question 8

What is the purpose of enamelin?

Answer 8

aid in enamel permeability

Question 9

What are enamel and dentin composed of?

Answer 9

hydroxyapatite crystals (enamel crystals are about 30 times larger than dentin crystals)

Question 10

How thick is the prism less enamel?

Answer 10

20 to 40 micrometers thick