Dentin

Question 1

Name some dentin-related changes that occur to the tooth with age.

Answer 1

• The pulp tissue becomes smaller due to the continual production of dentin
• The dentinal tubules patency decreases

Question 2

Name four differences between enamel and dentin.

Answer 2

• Dentin is sensitive
• Dentin continues to grow throughout life
• Dentin is softer than enamel
• Dentin has greater compressive and flexural strength

Question 3

What are the percentages of the gross components of dentin by volume?

Answer 3

50% mineralized, 30% organic matrix and 20% water

Question 4

What is the main component of the organic matrix in dentin?

Answer 4

Collagen, which makes up 90% of the organic matrix, mainly type 1. Collagen fibrils run parallel to the pulp surface and act as a scaffold for the mineralized component.

Question 5

What are the three contents of the dentinal tubules?

Answer 5

The cytoplasmic processes of the odontoblasts, afferent nerve axons and dentinal fluid.

Question 6

Where are the odontoblasts found and what is their function?

Answer 6

Odontoblasts are found in the outside of the pulp tissue, their role is to create and maintain the dentin matrix

Question 7

Name and describe two features of dentinal tubules.

Answer 7

• Primary curvatures, which are curves in the dentinal tubules formed due to a change in the direction of production of dentin matrix.
• Secondary curvatures, (much lesser amplitude than primary) which form contour lines of Owen when they coincide in adjacent tubules. They run concentrically around the teeth. (similar to Striae of Retzius)

Question 8

Do dentinal tubules have a smaller or larger lumen as they approach the dentin-enamel junction?
Do dentinal tubules branch closer to or further from the dentin-enamel junction?

Answer 8

• Smaller

- Closer

Question 9

What dentin surrounds the dentinal tubules? What are the features of this dentin?

Answer 9

Peritubular dentin; which lacks the collagen matrix but is more mineralized than inter-tubular dentin. As more peritubular dentin is laid down with age, the dentinal tubules decrease in size

Question 10

What dentin is found between the dentinal tubules?

Answer 10

Inter-tubular dentin

Question 11

Name the dentin that is un-mineralized? Where is this dentin found?

Answer 11

Pre-dentin, found closest to the odontoblasts

Question 12

What are the three types of mineralized dentin?

Answer 12

Primary dentin (mantle and circum-pulpal)
Secondary dentin 
Tertiary dentin (function - to repair and react to changes in dentin)

Question 13

How can tertiary dentin create dead tracks?

Answer 13

If the tertiary dentin has tubules which run in a different direction to those above, or have no tubules at all, this blocks the odontoblast process from reaching the tubules above.

Question 14

Is dentin production started before or after enamel?

Answer 14

Before!!!!!!

Question 15

What are the origins of odontoblasts?

Answer 15

Outer mesenchymal cells from the dental papilla

Question 16

The inner enamel epithelium cells (future ameloblasts) have what role in dentin production?

Answer 16

They induce the outer cells of the dental papilla to become odontoblasts, and produce dentin matrix. It is not until this matrix is mineralized that the inner enamel epithelium cells become ameloblasts.

Question 17

What is dentin production called?

Answer 17

Dentinogenesis

Question 18

When does dentinogenesis occur?

Answer 18

Bell stage of tooth development