Dentin

Question 1

What is the origin of Dentin?

Answer 1

Outer cells of the dental papilla; mesoderm.

Question 2

How is dentin formed?

Answer 2

1. Collagenous matrix from odontoblasts.

2. Maturation through mineralization (+hydroxyapatite)

Question 3

How long does the formation of dentin continue?

Answer 3

As long as the tooth is vital.

Question 4

Can dentin formation be stimulated by the environment?

Answer 4

Yes

Question 5

How is dentin formation stimulated by the environment?

Answer 5

1. Cutting away dentin near the DEJ stimulates odontoblasts.

2. Heavy handed scaling; removing all the cementum from root surface to stimulate tertiary dentin formation.

Question 6

What percentage of dentin is inorganic, organic, and water?

Answer 6

70% inorganic
20% organic (collagen
10% water

Question 7

What is the function of Dentin?

Answer 7

“Shock Absorber” most of the tooth is made up of dentin.

Question 8

What color is dentin?

Answer 8

yellow

Question 9

What type of union is made with the DEJ?

Answer 9

Scalloped

Question 10

Where are accessory foramina and Lateral canals found?

Answer 10

In the root portion of the tooth.

Question 11

What is the purpose of accessory foramina and lateral canals?

Answer 11

Transmits nervous/circulatory elements to the pulp proper of the tooth.

Question 12

What are the three components of mature dentin?

Answer 12

1. Dentinal tubules
2. Odontoblastic processes
3. Dentinal permeabilty.

Question 13

What is the orientation of dentinal tubules?

Answer 13

Travel from the pulp to the DEJ.

Question 14

What does the dentinal tubules contain?

Answer 14

Water, odontoblastic processes and sensory neurons.

Question 15

What is the correct unit for dentinal permeability?

Answer 15

tubules/mm^2

Question 16

What happens to odontoblasts as dentin is being formed?

Answer 16

Odontoblasts squeeze together to create a cross section that is about 20,000 tubules/mm^2.

Question 17

How does the cross section change as you get closer to the pulp?

Answer 17

The cross section grows to about 45,000 tubules/mm^2

Question 18

What are the types of dentin?

Answer 18

1. Peritubular
2. Intertubular
3. Circumpulpal

Question 19

What is the purpose of peritubular dentin?

Answer 19

Creates the walls of the dentin tubules.

Question 20

What is intertubular dentin?

Answer 20

Dentin between tubules (least mineralized)

Question 21

What is the purpose of circumpulpal dentin?

Answer 21

Surrounds the pulp chamber.

Question 22

Which type of dentin is the deepest in orientation, peritubular, intertubular, or circumpulpal?

Answer 22

Circumpulpal

Question 23

What are the three types of dentin based on formation?

Answer 23

Primary
Secondary
Tertiary

Question 24

How is primary dentin formed?

Answer 24

Formed before closing of the apical foramen (matrix)

Question 25

Where is secondary dentin formed?

Answer 25

Deposited at the pulpal periphery of the after the root is completed.

Question 26

When is tertiary dentin formed?

Answer 26

In response to noxious stimuli (iatorgenically:dentist or by dental caries)

Question 27

How is primary dentin mineralized?

Answer 27

Via odontogenesis

Question 28

How secondary dentin mineralized?

Answer 28

After primary dentin is mineralized, a second layer mineralizes over top with some areas of fusion.

Question 29

What is globular dentin?

Answer 29

Complete fusion of crystals from both primary and secondary mineralization.

Question 30

What is interglobular dentin?

Answer 30

Dentin closer to the DEJ; less calcified and mineralized.

Question 31

What are the 4 main microscopic features of dentin?

Answer 31

1. Imbrication lines of vonEbner 2. Contour lines of Owen 3. Neonatal line 4. Granular layer of Tomes

Question 32

What microscopic feature of dentin is associated with the trauma of birth?

Answer 32

Neonatal line

Question 33

What microscopic feature of dentin is associated with daily difference in apposition/maturation?

Answer 33

Imbrication lines of vonEbner

Question 34

What microscopic feature is located just deep to the CDJ and CEJ and is less calcified?

Answer 34

Granular layer of Tomes

Question 35

What microscopic feature of dentin is associated with trauma?

Answer 35

Contour lines of Owen

Question 36

Which microscopic feature of dentin is the most obvious?

Answer 36

Neonatal Line

Question 37

How is the Granular Layer of Tomes formed?

Answer 37

Via the process of maturation; you get less maturation during the first couple days of dentinogenesis therefore creating a line when more maturation occurs later in development.