Enamel

Question 1

What are the chemical properties of enamel in:
-mature enamel
-immature enamel

Answer 1

MATURE
- hydroxyapatite crystals
- Organic matrix (proteins)

IMMATURE
- enamel proteins

Question 2

What are the physical properties of enamel?

Answer 2

• v. Hard
• high resistance to abrasion
• brittle

Question 3

What is enamel almost entirely made up of?

Answer 3

Hydroxyapatite

Question 4

Name the enamel proteins (5)

Answer 4

1. Amelogenin
2. Ameloblastin
3. Enamelin
4. Tuftelin
5. Dentine Sialoprotein

Question 5

Describe the arrangement of the structural elements of the enamel.

Answer 5

-prismatic structure
-‘keyhole’ pattern
-enamel rods are the basic structural units
-prismatic head + tail

Question 6

How is the prismatic structure of enamel formed?

Answer 6

1. Amelogenesis starts at the bell stage of tooth development (ameloblasts differentiate & secrete enamel matrix)
2. Ameloblasts secrete enamel matrix (enamel proteins)
3. Mineralisation = hydroxyapatite crystals start forming in the enamel matrix
4. Formation of enamel rods/prisms

Question 7

Describe simply, the architecture of the ADJ

Answer 7

-barrier between enamel and dentine
-initial site of enamel/dentine deposition (cusps)
-‘scalloped pattern’

Question 8

What do the following do:
- enamel spindles
- enamel tufts
- enamel lamellae

Answer 8

ENAMEL SPINDLES
- DEJ
- dentine matrix surrounded by enamel
ENAMEL TUFTS
- DEJ
- hypomineralised structures (less mineralised)
ENAMEL LAMELLAE
- DEJ
- fine cracks
- due to incomplete maturation

Question 9

Explain how the microstructure of enamel can cause optical effects? And what are these called? Benefits?

Answer 9

Hunter-Schroeger Bands

• result from the varying arrangement & orientation of enamel rods/prisms
• direction changes = banding pattern
• more resistant to fracture

Question 10

What are the names of the long term incremental lines in enamel.

Answer 10

Striae of Retzius

Question 11

What are the names of the short term incremental lines in the enamel.

Answer 11

Perikymata

Question 12

What causes incremental lines in enamel.

Answer 12

Variations of daily deposition of enamel during tooth development.

Question 13

How does the ultrastructural features of enamel account for some of its physical properties?

Answer 13

ENAMEL RODS/PRISMS
- prismatic structure = hardness
HYDROXYAPATITE CRYSTALS
- hardness & resistance to wear

Question 14

How is the microporosity of enamel relevant to the development and progression of caries in enamel?

Answer 14

• small pores = acid to penetrate
• when pH low = hydroxyapatite crystals dissolve

Question 15

What’s gnarled enamel?

Answer 15

• enamel prisms forming spirals
• strength for occlusal forces

Question 16

Functions of amelogenin

Answer 16

-control of crystal morphology/organisation
-control enamel thickness

Question 17

Functions of ameloblastin

Answer 17

-‘cell adhesion protein’
-controls cell differentiation
- maintains enamel prism integrity

Question 18

Functions of enamelin

Answer 18

-formation of hydroxyapatite crystals

Question 19

Functions of tuftelin.

Answer 19

• cell signalling

Question 20

Functions of dentine sialoprotein

Answer 20

• initiation of mineralisation

Question 21

What are some differences to the structure in the outer layer of the enamel compared to the rest?

Answer 21

• non-prismatic (less susceptible to enamel)
• highly mineralise
• more fluoride