Enamel

Question 1

What forms enamel?

Answer 1

Ameloblasts

Question 2

What are 5 key features of enamel?

Answer 2

1. Hardest biological tissue
2. Abrasion resistance is high
3. Low tensile strength and brittle
4. Cannot be repaired or replaced
5. Avascular

Question 3

Where is enamel thickest on the tooth?

Answer 3

Over cusps and incisal edges

Question 4

Where is the enamel thinnest on the tooth?

Answer 4

Cervical margin

Question 5

What forms the mineral component of enamel?

Answer 5

Calcium hydroxyapatite crystals

Question 6

What 2 things form the organic component of enamel?

Answer 6

1. Amelogenins

2. Non-amelogenins

Question 7

What is the basic structural unit of enamel?

Answer 7

Enamel rods

Question 8

What forms enamel rods or interrod enamel?

Answer 8

Crystallites

Question 9

Where do enamel rods run?

Answer 9

Enamel-dentin junction to the surface of the tooth

Question 10

What is the main difference between rod and interrod composition?

Answer 10

Interrod crystals deviate 40° - 60° from crystals found in rods

Question 11

What pattern are enamel rods found in?

Answer 11

Keyhole pattern

Question 12

What is the name of the banding pattern found in enamel?

Answer 12

Hunter-Schraeger bands

Question 13

What are 2 functions of Hunter-Schraeger bands?

Answer 13

1. Strengthen enamel

2. Prevent cracks from propagating through tooth

Question 14

How do Hunter-Schraeger bands arise?

Answer 14

10-13 layers of rods follow the same direction but blocks above and below follow paths in different directions

Question 15

What 3 things cause incremental lines to appear?

Answer 15

1. Changes in enamel secretory rhythm
2. Chemical composition of enamel
3. Position of the developing enamel front

Question 16

What are 2 types of incremental lines?

Answer 16

1. Cross striations (short period)

2. Enamel striae (long period)

Question 17

What are cross striations?

Answer 17

Lines which cross enamel rods at right angles to their long axes

Question 18

What are striae of Retzius?

Answer 18

Prominent lines which run obliquely across the enamel rods to the surface

Question 19

What forms striae of Retzius?

Answer 19

Successive positions of the enamel-forming front

Question 20

How do striae of Retzius appear in transverse section?

Answer 20

Concentric rings

Question 21

What is the neonatal line?

Answer 21

Marked stria formed at birth reflecting the metabolic changes which occur at birth

Question 22

What are perikymata?

Answer 22

Shallow grooves that run circumferentially around the crown

Question 23

What controls amelogenesis?

Answer 23

Genetic control

Question 24

What are the 4 stages of amelogenesis?

Answer 24

1. Pre-secretory
2. Secretory
3. Maturation
4. Post-maturation

Question 25

What are 2 stages of the pre-secretory stage of amelogenesis?

Answer 25

1. Cells of internal enamel epithelium differentiate into ameloblasts 2. Cells become reversed in terms of polarity - Nucleus moves to top

Question 26

What are 3 stages of the secretory stage of amelogenesis?

Answer 26

1. Ameloblasts form aprismatic enamel 2. Secretory pole forms Tomes process, where crystallites are formed 3. Nuclei move towards Tomes process

Question 27

What occurs during the maturation stage of amelogenesis?

Answer 27

Ameloblasts die and are phagocytosed

Question 28

What occurs during the post-maturation stage of amelogenesis?

Answer 28

Ameloblasts regress in height and serve to protect enamel during eruption

Question 29

What is attrition?

Answer 29

Tooth loss involving tooth to tooth contact

Question 30

What is abrasion?

Answer 30

Tooth loss involving friction between tooth and outside material

Question 31

What is erosion?

Answer 31

Tooth loss involving contact with acidic agents

Question 32

What are 2 causes of intrinsic enamel loss?

Answer 32

1. Acid reflux | 2. Bulimia

Question 33

What are 2 causes of extrinsic enamel loss?

Answer 33

1. Sugar | 2. Fizzy drinks

Question 34

What is dental caries?

Answer 34

Demineralisation of enamel

Question 35

What happens when plaque becomes mineralised?

Answer 35

It forms a calculus