(4) Dentino-pulpal Complex

Question 1

What forms the bulk of the tooth?

Answer 1

Dentine

Question 2

Is dentine a live tissue?

Answer 2

yes!
Forms throughout life

Question 3

What cells form dentine?

Answer 3

odontoblasts

Question 4

Where are the parallel tubules located in dentine?

Answer 4

Mineralised collagen matrix

Question 5

What is dentine harder than?

Answer 5

Harder than bone and cementum

Question 6

What makes dentine so strong?

Answer 6

Its tubular nature renders it strong (high compressive, tensile and flexural strength).

Question 7

What are the percentages of inorganic, inorganic and water in dentine?

Answer 7

Dentine is composed of 70% inorganic component, 20% organic component and 10% water by weight.

Question 8

Why is dentine more soluble than enamel?

Answer 8

The hydroxyapatite is more carbonate rich
Smaller than enamel

Question 9

Where are the crystals found in dentine?

Answer 9

crystals are found on and between collagen fibrils.

Question 10

What are the organic components of dentine?

Answer 10

Collagen (mainly type I) forms 90% of the organic component.

Dentine phospho-proteins, proteoglycans and other proteins are also present.

Question 11

What is the chemical composition of dentine?

Answer 11

Hydroxyapatite crystals

Question 12

What forms over 90% of the organic matrix

Answer 12

Collagen type l

Question 13

What is the main phosphoprotein of denting

Answer 13

Phosphophoryn/ dentin phospho-protein

most acidic protein known and can bind calcium ions

Allows it to be important in mineralisation

Question 14

What is a feature of phosphophoryn?

Answer 14

Due to its high calcium ion binding properties, it has been implicated in mineralisation.

Question 15

What are the main proteoglycans of dentin?

Answer 15

biglycans and decorin

Question 16

What is the role of proteoglycans is dentin?

Answer 16

Proteoglycans have an important role in collagen assembly, cell adhesion, migration, differentiation and proliferation.

Question 17

What are the main glycosaminoglycans of dentin?

Answer 17

chondroitin-4- sulphate and chondroitin-6-sulphate.

Question 18

What are other acidic components of the organic matrix of dentin?

Answer 18

osteonectin, osteopontin

Question 19

What are some growth factors found in dentin?

Answer 19

insulin-like growth factor and transforming growth factor. They are absorbed from circulating tissue fluid.

Question 20

What are phospholipid thought to be involved in?

Answer 20

involved in the formation and growth of apatite crystals. - organic matrix

Question 21

Where do denting tubules extend from and to?

Answer 21

Dentinal tubules extend from the pulp surface to the amelo- dentinal and the cemento-dentinal junctions.

Question 22

What course do the dentin tubules follow?

Answer 22

Curved sigmoid course

Primary curvature

Question 23

Name structures A and B

Answer 23

Question 24

What type of section is shown here?

Answer 24

Cross section

Partial demineralised section

Question 25

Name structures A-C

Answer 25

Question 26

What side of the dentin is thicker and which is thinner?

Answer 26

The tubules are 2.5μm in diameter at the pulpal end and 1μm or less at the Enamel end.

Question 27

Why do the dentin tubules become closer together at the pulpal end?

Answer 27

As the odontoblasts retreat inwards, they occupy a smaller area, thus the tubules become closer to each others.

Question 28

What cross-sectional area occupies more dentin tubules, enamel-dentin junction or the pulps end?

Answer 28

PULPAL END 22% of the cross sectional area near the pulp is occupied by dentinal tubules. * 2.5% at the enamel-dentine junction.

Question 29

What does this image show?

Answer 29

Contour lines of Owen Secondary curvatures, if they coincide in adjacent tubules they give rise to contour lines of Owen (arrowed).

Question 30

Where do dentin tubules branch?

Answer 30

near enamel-dentine junction

Question 31

What happens to terminal branches at the root?

Answer 31

They loop

Question 32

What forms the wall of the newly formed dentin tubule at the pulp?

Answer 32

Mineralised type 1 collagen

Question 33

What is called intratubular dentin?

Answer 33

Tubules are lined with peritubular (intratubular) dentin consisting of a layer of highly mineralized matrix material made primarily of apatite crystals. The intertubular dentin, which lies between the tubules, is a less-calcified matrix that consists of some apatite crystals embedded within a collagen matrix. Maturation Reduces size of lumen

Question 34

What is the role of the organic dentin phospho-proteins?

Answer 34

Only present in small amounts Integral in the mineralisation of dentin