Dentine

Question 1

What is the composition of dentine?

Answer 1

65-70% inorganic hydroxyapatite, 20% organic matrix and 10% water.
Collagen fibres make up mostly all of the organic matrix with principal collagen fibre is type 1

Question 2

What is mantle dentine?

Answer 2

The first formed in the crown and most peripheral layer beneath the enamel.

Question 3

What is circumpulpal dentine?

Answer 3

Forms the bulk of the dentine between the mantle layer and zone of mineralisation, typically in outer part of the crown

Question 4

How does interglobular dentine result?

Answer 4

When calcospherites do not fuse completely with the advancing mineralisation front

Question 5

What is predentine?

Answer 5

Innermost un-mineralised layer, where new dentine is being deposited throughout life.

Question 6

What appearance does predentine have when dyed with haematoxylin and eosin?

Answer 6

Pale appearance

Question 7

What is secondary dentine?

Answer 7

Seen in older teeth at the inner, pulpal part of the circumpulpal dentine, continuous with primary dentine

Question 8

What is tertiary dentine?

Answer 8

Hard tissue deposited on the pulpal surface in response to an external stimulus (caries, attrition) - provides a barrier to the progress of caries and toxins

Question 9

What is reparative dentine?

Answer 9

Dentine forming after a stimulus has killed the original odontoblasts, these cells differentiate from odontoblast like stem cells, much more irregular than circumpulpal dentine

Question 10

What results in 20um spaced Andresen lines?

Answer 10

Changes in collagen fibril orientation

Question 11

What are short period markings seen as alternating light and dark bands called?

Answer 11

Von Ebner lines

Question 12

What are lines associated with the primary curvatures of the dentinal tubules called?

Answer 12

Schreger lines

Question 13

What are lines associated with the secondary curvatures of dentinal tubules called?

Answer 13

Contour lines of Owen

Question 14

What physical property differs dentine from enamel?

Answer 14

Dentine is flexible

Question 15

Where do dentinal tubules run?

Answer 15

From the pulpal surface to the enamel-dentine and cementum-dentine junctions.

Question 16

What dentine is deposited on the walls of dentinal tubules to make their lumens smaller?

Answer 16

Peritubular dentine

Question 17

What shape are primary curvatures of dentinal tubules?

Answer 17

Curved and sigmoid

Question 18

Do secondary curvatures have smaller changes in direction of the tubules?

Answer 18

Yes

Question 19

What may be responsible for the appearance of the granular layer of Tomes?

Answer 19

Looping of the terminal part of the tubules

Question 20

Do dentinal tubules get longer or shorter going from the pulp to the EDJ?

Answer 20

Shorter

Question 21

Does dentine formation begin before enamel?

Answer 21

Yes

Question 22

Which surface is the most recently formed dentine on?

Answer 22

Pulpal and is called pre-dentine

Question 23

Does dentine formation continue after tooth eruption?

Answer 23

Yes and throughout the life of the pulp

Question 24

What is the second most abundant constituent of dentine?

Answer 24

Dentine phosphoprotein

Question 25

How does the amount of translucent dentine change with age?

Answer 25

Increases

Question 26

How does peritubular dentine differ from intertubular dentine?

Answer 26

Lacks a collagenous fibrous matrix and is more mineralised than intertubular dentine

Question 27

How do dead tracts form?

Answer 27

Primary odontoblasts are killed by an external stimulus, the empty tubules remain air filled and transmitted light under the microscope will be internally reflected and the tubules appear as dark tracts.

Question 28

What are the three proposed mechanisms of dentine sensitivity?

Answer 28

1) Direct innervation
2) Odontoblasts acting as sensory endings
3) Hydrodynamics (fluid flow)

Question 29

What is the hydrodynamic fluid flow theory?

Answer 29

An effective stimulus triggers a flow of fluid within the tubules, the movement being sufficient to depolarise nerve endings either within the inner parts of tubules or between odontoblasts at the pulp-predentine junction and to the subodontoblastic neural plexus.

Question 30

Where is interglobular dentine found adjacent to?

Answer 30

Mantle layer in the crown