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Dentin Flashcards

1
Q

What are some differences between Dentin and Pulp?

A 
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
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2
Q

Clinical significance of Dentin

A

Protects both the enamel and pulp

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3
Q

How does Dentin protect enamel

A

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

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4
Q

Describe the appearance of the DEJ at the crown

A

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

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5
Q

When does Dentinogeneis occur?

A

During the “Bell stage” of tooth development

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6
Q

What occurs just prior to dentinogenesis?

A

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

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7
Q

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

A

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

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8
Q

What direction does dentinogenesis occur?

A

From cusp tip to cervix

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9
Q

Odontoblast differentiation

A

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

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10
Q

What induces odontoblast differentiation

A

Inductive signals for odontoblast differentiation

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11
Q

Where do signals for odontoblast differentiation come from?

A

From the enamel organ - most likely the enamel knot

This signal induces several molecules

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12
Q

Wnt10a

A

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

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13
Q

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

A

False - it is most likely just one of many

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14
Q

What is required for dentin mineralization?

A

Ca+2
Phosphate-
Initiation fo crystal formation

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15
Q

Where does Ca+2 come from for dentin mineralizaiton?

A

Free ions in plasma

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16
Q

Where does the phosphate come from for dentin mineralization?

A

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

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17
Q

How is Ca and phosphate transported?

A

It is transported into predentin through and between odontoblasts

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18
Q

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

A

False - It requires special mechanisms:
Mantle
Circumpulpal

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19
Q

Mantle dentin formation

A 
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
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20
Q

Mantle dentin mineralization

A

Mineralized by matrix vesicles

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21
Q

Matrix vesicles

A

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

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22
Q

How does dentin form?

A

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

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23
Q

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

A

True

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24
Q

Circumpulpal dentin formation

A

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
31
What is the size of dentin crystals and how does that compare to enamel?
10x35x100nm | Much smaller than enamel crystals
32
Organic phase of dentin
Made of collagen and noncollagen proteins (90% type I collagen)
33
What are the types of proteins found in dentin?
Non-tissue specific proteins Mineralized tissue-specific proteins Dentin-dominant proteins
34
What are non-tissue specific proteins in dentin?
Proteoglycans | Signaling molecules/growth factors
35
What are mineralized tissue-specific proteins in dentin?
Osteocalcin | Bone sialoprotein
36
What are dentin-dominant proteins
Dentin matrix protein I Dentin glycoprotein Dentin sialoprotein Dentin phosphoprotein
37
Dentin sialoprotein
5-8% of non-collagen proteins in dentin | Function is not well understood
38
Dentin phosphoprotein
>50% of non-collagen proteins in dentin Anionic Includes chain of polar amino acid repeates Serines are phosphoryated
39
What gene codes for Dentin phosphoprotein
DSPP (Dentin sialophosphoprotein)
40
Human hereditary disorder
aka Dentinogenesis Imperfecta Dentin forms improperly 1:6,000-8,000 Associated with mutations of DSPP
41
How does Dentinogenesis Imperfecta defer in humans and mice?
In mice: there are 2 alleles, and both need to be negative for there to be abnormal dentin In humams: DI is dominantly inherited with DSPP mutation
42
What are the 2 types of mutations to cause DI in humans?
1) changes in the first 3 amino acids critical for moving DSPP through the rough ER 2) Small base pair deletions produce frameshifts coding the DPP molecule that contain polar AA repeat - they become uncharged
43
What is the result of the mutations that cause DI
Result in abnormal DSPP cannot be released from odontoblasts - also traps normal proteins made by the unaffected chromosome, making it a dominant negative mutaiton
44
Dentinal tubules
At right angles to DEJ S-shaped in crown, straighter in the root Have terminal and lateral branches
45
Contents of dentinal tubules
``` Fluid (mostly water) Nerve fibers Odontobalstic processes Very few collagen fibers Non-cellular lining sheath ```
46
How do dentin tubules differ near the DEJ to the PD border?
Diameter of tubule is larger close to PD border Number of tubules is greater close to PD border Tubules occupy less area at DEJ than PD border Permeability and wetness increase toward the PD border
47
What are the different types of dentin based off of?
When they're formed Location Histological features
48
Primary dentin
Dentin formed until the completion of root dentin Comprises most of dentin (both mantle and circumpulpal) 20u-150u at DEJ
49
Secondary dentin
``` Formed after root development Forms slowly but throughout life Central to primary dentin Similar in structure to primary dentin In circumpulpal dentin Likely formed by initial odontoblasts ```
50
Tertiary dentin
Produced in specific locaiton in response to noxious stimuli Structurally irregular - may or may not have tubules and may include cells Thought that initial odontobalsts are killed, and new ones come in for tertiary dentin
51
Intertubular dentin
Between tubules | Found in primary and secondary dentin
52
Intratubular/Peritubular dentin
Lines tubules | Found in primary and secondary dentin
53
What are some differences between intertubular and intratubular dentin?
Intratubular dentin covers less volume Intratubular dentin is much more mineralized Intratubular ring is wider near DEJ - tubule is narrower here
54
Translucent dentin
Tubules are completely filed with intratubular dentin | Normal process of aging
55
Sclerotic dentin
Tubules are completely filled with intratubular dentin | Accelerated ddeposition due to caries or attrition
56
Dead tracts
Tubules are dried out and become filled with air
57
Interglobular dentin
Hypomineralized dentin just below the mantle dentin
58
Growth lines
Reflect incremental pattern of deposition | Can be exaggerated due to tetracycline treatment

Oral Histology (12 decks)

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