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Flashcards in Dentin Deck (58)
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1

What are some differences between Dentin and Pulp?

Pulp = soft connective tissue with blood vessels, whole cells, and is non-mineralized
Dentin = minneralized connective tissue covering the pulp with no blood vessels or whole cells. It does have nerve endings and odontoblastic processes

2

Clinical significance of Dentin

Protects both the enamel and pulp

3

How does Dentin protect enamel

It is softer and more compressive, so it can cushion the more brittle enamel

4

Describe the appearance of the DEJ at the crown

It is scalloped, which facilitates adhesion of dentin and enamel to one another

5

When does Dentinogeneis occur?

During the "Bell stage" of tooth development

6

What occurs just prior to dentinogenesis?

Tissue layers of the dental organ are present
Crown outline is present
There are no odontoblasts or ameloblasts

7

What occurs in the late bell stage in regards to dentinogenesis?

Inner enamel cells (which become ameloblasts) are present
Undifferentiated mesenchumal cells are present in the dental papilla (become odontoblasts)
Dentin is secreted, and then enamel is secreted

8

What direction does dentinogenesis occur?

From cusp tip to cervix

9

Odontoblast differentiation

Begin as mesenchymal cells
One cell will divide to become a preodontoblast and a fibroblast
When preodontoblast begins to secrete matrix, it is an odontoblast

10

What induces odontoblast differentiation

Inductive signals for odontoblast differentiation

11

Where do signals for odontoblast differentiation come from?

From the enamel organ - most likely the enamel knot
This signal induces several molecules

12

Wnt10a

One of the growth factors implicated by the enamel knot
First expressed in the not, then in pre-odontoblast at the cusp tip.
Then it is successively expressed in the more cervical parts of the teeth
Expression immediately precedes the wave of odontoblast differentiation

13

T/F - Wnt10a is the only molecule implicated in inducing odontoblast differentiation

False - it is most likely just one of many

14

What is required for dentin mineralization?

Ca+2
Phosphate-
Initiation fo crystal formation

15

Where does Ca+2 come from for dentin mineralizaiton?

Free ions in plasma

16

Where does the phosphate come from for dentin mineralization?

From plasma and cleavage of organic molecules containing phosphate in odontoblasts by alkaline phosphatase

17

How is Ca and phosphate transported?

It is transported into predentin through and between odontoblasts

18

T/F - The presence of requisite ions are sufficient to initiate crystal formation

False - It requires special mechanisms:
Mantle
Circumpulpal

19

Mantle dentin formation

Initial layer of dentin near the DEJ
Principle component is Type I collagen
Secreted by odontoblasts
Relatively large fibrils
Oriented perpendicular to the basal lamina/future DEJ

20

Mantle dentin mineralization

Mineralized by matrix vesicles

21

Matrix vesicles

Membrane bound vesicles synthesized by odontobalsts
Concentrate Ca and PO containing and other organic molecules
Help mineralize Mantle dentin

22

How does dentin form?

Odontobalsts secrete matrix, which then mineralizes
Odontoblasts grow, and their processes elongate - this creates a barrier between dentin and pulp
Odontoblasts migrate toward pulp

23

T/F - Near the end of mantle formation, once odontoblast process becomes dominant

True

24

Circumpulpal dentin formation

Interior to mantle - much thicker
Process is the same as mantle formation

25

What is the difference between formation of Mantle and Circumpulpal dentin formation

Circumpulpal has smaller fibrils than Mantle
Circumpulpal is secreted parrallel to basal lamina, Mantle is perp.
Circumpulpal is mineralized by proteins, Mantle is mineralized by matrix vesicles

26

What are functional consequences of developmental differences between Mantle and Circumpulpal dentin

Mantle is more organic
Mantle is less mineralized
DEJ is more vulnerable to caries

27

Dentin phosphoprotein

Relatively spcific to dentin
Prominent dentin protein
Highly phosphorylated
High in serine/aspartic acid
Acidic
Thought to precipitate Ca to initiate mineralization

28

Dentin constituents by weight

70% inorganic
20% organic
10% water

29

Dentin constituents by volume

45% inorganic
33% organic
22% water

30

Mineral phase of dentin

Hydroxyapatite crystals
1000s of unit cells/crystal
Crystals are randomly oriented - enamel is organized