(2) Anatomy and Histology of the Periodontium - Enamel interactions (C)

Question 1

What is characteristic of the enamel-dentin junction?

Answer 1

Enamel-dentine junction has a scalloped pattern

Question 2

What is shown in the histogram?

Answer 2

enamel dentin junction

Question 3

Name structures A and B

Answer 3

A = enamel
B = dentin

Question 4

Where would you find the scalloped interface of the EDJ?

Answer 4

Where shearing forces are high

beneath cusps and incisal edges

scalloped patterns increases strength

Question 5

What direction would stria of Retzius run in this ground section?

Answer 5

left to right

(prisms run top to bottom)

Question 6

What are enamel spindles?

Answer 6

Narrow, round tubules 8μm in diameter.

They extend up to 25um into the enamel.

Most commonly beneath cusps.

Question 7

What is shown in this diagram?

Answer 7

enamel spindles

Question 8

Where do enamel spindles commonly locate?

Answer 8

Most commonly beneath cusps.

Question 9

How do enamel spindles arise?

Answer 9

pushing of the odontoblasts (cells that produce dentin) into newly formed enamel

these are remnants of the odontoblastic processes

Question 10

How does the gnarled enamel form?

Answer 10

by the crowding of the ameloblasts

Question 11

What is shown in this histogram?

Answer 11

enamel tufts

Question 12

What is an enamel tuft?

Answer 12

Junctional structures in the inner third of enamel that resemble tufts of grass

Question 13

What do tufts form in the same direction as?

Answer 13

They have the same direction as enamel prisms

Question 14

What is the mineralised like of enamel tufts?

Answer 14

They are hypomineralised

Question 15

What are tufts made from?

Answer 15

thought to be residual matrix protein at the prism boundaries.

Question 16

What type of protein is a tuft?

Answer 16

minor non-amelogenin protein.

Question 17

What is shown in this histogram?

Answer 17

lamellae

Question 18

What is an enamel lamellae?

Answer 18

Structural faults that run through the entire thickness of the enamel.

Incomplete maturation of groups of prisms.

Question 19

What can enamel lamellae be confused with?

Answer 19

Should not be confused with cracks produced during ground section preparation.

Question 20

What type of mineralisation do enamel lamellae have?

Answer 20

Hypomineralised areas.

Question 21

What are the enamel micro-porosities filled with?

Answer 21

Enamel pores are water filled spaces between the crystallites.
Enamel porosity makes 3-5% by volume.

Question 22

Where are large enamel pores found?

Answer 22

Larger pores at prism boundaries.

Question 23

What are the 3 arrangements between the cementum and enamel?

Answer 23

Pattern 1: the cementum overlaps the enamel (60%).

Pattern 2: the cementum and enamel meet at butt joint (30%).

Pattern 3: cementum and enamel fail to meet and the dentine between them is exposed (10%).

Question 24

What always overlaps in the cement-enamel junctions?

Answer 24

the cementum always overlaps enamel as the enamel forms first

Question 25

Name A-C and the black and orange arrows

Answer 25

Ground Section
A = Enamel
B= Dentine
C= Acellular cementum

Black arrows point to interglobular dentine

Orange arrows point to the granular layer of Tomes

Question 26

What happens to translucency of enamel with age?

Answer 26

increases with age and staining = yellow

Question 27

Does the composition of enamel change as we age?

Answer 27

The composition of surface enamel changes as a result of exchanges with the oral fluids.

Question 28

Do caries increase or decrease as we get older?

Answer 28

There is a decrease in caries due to enhanced mineralisation

e.g. fluoride