Enamel

Question 1

What is enamel made of

Answer 1

Hydroxyapatite crystals 95%
Water 4%
Proteins 1%

Question 2

Shape of enamel prism?

Answer 2

Keyhole shaped

Question 3

Physical characteristics of enamel

Answer 3

• thickest at the incisal edge and thinnest at the cervical margin
  -hardest tissue in the body , resists abrasion
• brittle
• Highly mineralised
• cannot be repaired or replaced

Question 4

Surface enamel vs subsurface enamel

Answer 4

Surface enamel is thicker, less porous and harder, denser
Surface enamel contains more fluoride ions but less magnitude/ carbonate ions

Question 5

Why does translucency of enamel increase with age?

Answer 5

Less internal reflection, dentine shows through, demineralisation

Question 6

Principal mineral component of enamel ?

Answer 6

Calcium hydroxyapatite

Question 7

What is the cell that forms organic template of enamel?

Answer 7

Ameloblast

Question 8

Basic structural unit of enamel

Answer 8

Enamel prism or rod

Question 9

What is the difference between attrition and abrasion?

Answer 9

Attrition is tooth loss involving tooth to tooth contact eg. Bruxism

Abrasion is tooth loss involving friction between tooth and outside material eg. Over brushing or use of abrasive toothpaste

Question 10

Differences between dentine and enamel crystals

Answer 10

Dentine crystals are smaller
Scallop structure at the dentine-enamel junction

Question 11

Why does fluoride help

Answer 11

Fluoride ions replace OH ions to form fluroroapatite which is more stable than hydroxyapatite

Question 12

Why is enamel able to withstand the shearing forces even though it is brittle?

Answer 12

It is supported by dentine. Never leave enamel unsupported after any procedure, consultant will fail you

Question 13

Where are teeth formed from?

Answer 13

Tooth bud

Question 14

What does ameloblasts secrete

Answer 14

-secrete an organic matrix comprised primarily of several enamel proteins including amelogenin (90%) ameloblastin (5%) and enamelin. This matrix then undergoes mineralisation

Question 15

Some histological slides do not have enamel shown, why?

Answer 15

Enamel is mainly composed of mineral, ie hydroxyapatite. Some slides are Demineralised specimens so the entire enamel is not shown on the slide.

Question 16

How to differentiate between dentine and enamel on a slide?

Answer 16

1. Striae of retzius (oblique striations in enamel)
2. Cross striations (little lines in each enamel rod)
3. Pointy bit of the scallop faces enamel
4. Space between dentinal tubules are larger than spacing between enamel rods at ADJ

Question 17

Is enamel brown?

Answer 17

No, enamel is translucent. It appears brown on the slide because of the light and sectioning

Question 18

Abfraction

Answer 18

When the ADJ fractures and the enamel pops out

Question 19

What is the characteristic of enamel at the fissures

Answer 19

It is thinner, the enamel rods

Question 20

What are ground sections

Answer 20

Hard Mineralised tissues remain intact

Question 21

How does enamel differ from all other calcified tissues in the body

Answer 21

It does not have cells within it or on its surface

Question 22

Where is enamel the thinnest?

Answer 22

Cervical margin. Rmb that there is no enamel at the apex

Question 23

Does the mineral content increase or decrease from the ADJ to the surface

Answer 23

Increases

Question 24

What are so common ions that are present in enamel

Answer 24

Fluoride magnesium carbonate

Question 25

Two main types of incremental lines in enamel

Answer 25

Cross striations and Striae of Retzius

Question 26

Dentine is more vulnerable at this site.

Answer 26

Enamel is thinner at the fissure so caries more likely at fissures

Question 27

Enamel rod direction

Answer 27

The rod direction in the crown is normally perpendicular to the incisal surface

Question 28

Four enamel proteins

Answer 28

Amelogenins, ameloblastins,enamelins, tuftelins

Question 29

Does enamel contain collagen

Answer 29

No

Question 30

Tomes processes

Answer 30

Right angle deposition ?