Dentine Structure

Question 1

Describe the inorganic composition of dentine

Answer 1

70% weight, 50% volume:

Calcium hydroxyapatite
Hexagonal prisms
Found on and between collagen fibrils

Question 2

Describe the organic composition of dentine

Answer 2

20% weight, 30% volume

90% collagen type 1 (large diameter)
Traces of collagen type 3 and 5
8% non-collagenous proteins
2% lipids

Question 3

What percentage of dentine is made up of water

Answer 3

10% weight, 20% volume

Question 4

How does the composition of dentine present problems for bonding composites?

Answer 4

Dentine has a wet environment due to fluid flow and outward fluid limits the penetration of bonding agents. BUT composite fillings are hydrophobic.

Bond has to cope with 2 types of materials - both the mineral and organic elements of dentine.

Bond has to cope with the flexion and resist the movement.

Question 5

What two types of dentine is found in the coronal dentine/crown?

Answer 5

Mantle dentine

Circumpulpal dentine

Question 6

What 3 types of dentine is found in radicular dentine?

Answer 6

Hyaline layer
Granular layer
Circumpulpal dentine

Question 7

What 2 types of dentine can be considered primary dentine?

Answer 7

Mantle dentine and circumpulpal dentine

Question 8

What dentine is a type of secondary dentine?

Answer 8

Circumpulpal dentine

Question 9

Describe the appearance of dentine under a transmission microscope

Answer 9

Primary curvature: curved, sigmoid course from enamel-dentine.

Secondary curvature: changes direction every few micrometres. Forms contour line of Owen when these coincide in adjacent tubules.

Question 10

What are the contour lines of Owen?

Answer 10

They are accentuated incremental lines in the dentine thought to be due to disturbances in the mineralisation process.

Question 11

What is a Schreger line?

Answer 11

They are alternating light and dark lines seen in enamel that begin at the EDJ and end before they reach the surface

These may be where enamel rods were cut across rather than along.

(like rings in a tree trunk)

Question 12

Where can marked branching of dentine tubules be seen?

Answer 12

Just below the EDJ in the mantle dentine

OR can be visible in unmineralised predentine

Question 13

What is responsible for creating the granular layer of Tomes in root dentine?

Answer 13

Branching and loops in the dentine.

They reflect a major interruption in the deposition of dentine due to a metabolic disruption during odontogenesis.