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D1 Spring - Histopathology > Week 4 - Dentin > Flashcards

Week 4 - Dentin Flashcards

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1
Q

What three things are dentin made of?

A

70% Mineral
20% organic
10% water

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2
Q

What minerals is dentin made of?

A
  • Calcium Hydroxyapatite [Ca10(PO4)6(OH)2]
  • Trace amounts of calcium carbonate, fluoride,
    magnesium and zinc
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3
Q

What organic material is dentin made of?

A
  • 50% of noncollagenous proteins are phosphoprotein
  • Sialoprotein and sialophosphoprotein
  • Proteoglycans and glycosaminoglycans
  • Osteonectin and osteopontin
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4
Q

What collagen does dentin have?

A

Type I
With trace amounts of type III and V

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5
Q

How is the type I collagen of dentin slightly different than that of bone?

A
  • Higher ratio of proline and hydroxyproline
  • Higher prevalence of molecular cross-linking
  • Higher level of bound water (Mainly this)
  • Random orientation of the hydroxyapatite crystals (also mainly this)
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6
Q

What non-collagenous proteins does dentin include?

A

Proteoglycans
Glycosaminoglycans
Carboxyglutamate containing protein
Osteonectin
Osteopontin

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7
Q

What are examples of proteoglycans?

A

Biglycan
Decorin

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8
Q

What are types of glycosaminoglycans?

A
  • Chondroitin-4- sulfate
  • Chondroitin-6- sulfate
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9
Q

What are non-collagenous proteins necessary for?

A

Initiation
They control size of crystals

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10
Q

What does osteopontin contain?

A

The receptor binding sequence Arginine-Glycine-
Asparagine (Arg-Gly-Asp or a.k.a. the RGD binding complex)

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11
Q

What are the 4 life cycle stages of the odontoblast?

A

Pre-odontoblast
Secretory Odontoblast
Transitional Odontoblast
Resting Odontoblast

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12
Q

What does the transitional odontoblast stage become?

A

Autophagic

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13
Q

Stimulus for ectomesenchymal cell differentiation into pre-odontoblasts appears to be derived from

A

Fibronectin located within the basal lamina of the inner enamel epithelium (IEE) - and several growth factors from the IEE

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14
Q

What is the function of pre-odontoblastic fibronectin receeptors?

A

Allows the cells to align themselves along the basal lamina, assume polarity, and differentiate into secretory cell

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15
Q

Growth factors secreted by the IEE that play a roll
in odontoblast differentiation include:

A
  • Transforming Growth Factor (TGF)
  • Bone Morphogenetic Protein (BMP)
  • Insulin-like Growth Factor (IGF)
  • Fibroblast Growth Factor (FGF)
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16
Q

What does complete differentiation require?

A

A set number of cell divisions which allows cells to express appropriate receptors able to bind growth factors localized to the IEE basal lamina

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17
Q

What does last minute division of odontoblast differentiation result in?

A

a mature odontoblast
and a daughter cell that is forced into the subodontoblastic cell layer

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18
Q

What is the “backup layer” after the pre-odontoblastic layer?

A

Subodontoblastic layer

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19
Q

What do subodontoblastic layer cells represent?

A

Ectomesenchymal cells exposed to the entire cascade of developmental controls for odontoblastic differentiation

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20
Q

What cell population is responsible for the reparative odontoblasts that differentiate from pulpal cells?

A

Cells in the subodontoblastic layer

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21
Q

What cells make up the secretory odontoblast?

A

Tall columnar cells with extensive junctional complex and gap junction formations

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22
Q

What stage exhibits significant alkaline phosphatase activity?

A

Secretory odontoblast

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23
Q

What collagen is secreted during the secretory odontoblast stage?

A

Type I and traces of type III and type V collagen

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24
Q

What matrix vesicles are secreted in the secretory odontoblast stage?

A
  • Alkaline phosphatase
  • Ca ++ and PO4-
  • Annexin
  • Calcium hydroxyapatite crystallites
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25
What does annexin mediate?
flow of Ca++ into the matrix vesicle. Also serves as a collagen receptor that binds matrix vesicles to collagen
26
What is mantle dentin?
First formed dentin
27
What kind of collagen makes up the mantle dentin?
Type I and III collagen
28
How are collagen fibers in mantle dentin arranged?
Perpendicular to the basal lamina of the IEE
29
What is mantle dentin secreted by?
Secondary odontoblasts
30
How is organic matrix of dentin deposited?
Incrementally at a rate of 4 micrometers to 8 mcm per 24 hours
31
What do incremental lines in dentin (lines of von Ebner) represent?
A hesitation in matrix formation and subsequently altered mineralization that occur after 4-20 days of matrix deposition
32
What causes incremental lines (e.g., neonatal line, contour lines of owen) or areas of interglobular dentin?
Deficiencies and irregularities in dentinogenesis, resulting in areas of hypomineralization
33
Where are dentinal tubules tapered to?
* 2.5 µm diameter at the pulpal surface * 1.2 µm diameter at midlength * 0.9 µm near the DEJ Narrower at DEJ, wider at pulpal surface
34
Where are dentin tubules more and less at?
More at pulp Less at DEJ
35
What is peritubular dentin?
Denser, more calcified and resistant than intertubular dentin
36
Where do cell processes branch?
They anastamose at basement membrane
37
What is interglobular dentin?
A zone of globular, rather than linear, formed dentin in the crowns of teeth
38
What is interglobular dentin characterized by?
interglobular spaces that are unmineralized or hypomineralized dentin between normal calcified dentinal layers
39
What is the tome's granular layer?
A granular-appearing layer in the dentin of the root adjacent to the cementum
40
What is tome's granular layer comprised of?
Hypomineralized interglobular dentin
41
What is primary dentin?
All dentin (except mantle dentin) formed up to the time the tooth achieves functional occlusion
42
What is secondary dentin?
All dentin formed (except tertiary dentin) formed after tooth achieves functional occlusion
43
What are dead tracts?
Dentinal tubules that are void of the odontoblastic process
44
What are dead tracts filled with?
Air or organic debris (or empty) and look black in transmitted light microscopy
45
What is sclerotic dentin?
Dentin in which the tubules are occluded with mineral The dentin is non-tubular and is nearly transparent
46
When does the incidence of sclerotic dentin increase?
With age May also be tertiary (reparative) dentin
47
When do lines of Von Ebner occur?
4-20 days of matrix deposition
48
What do von ebner lines represent?
hesitations in matrix deposition and therefore altered mineralization
49
What do neonatal lines and contour lines of owen represent?
Both represent exaggerated lines of von Ebner that occur during periods of altered cell metabolism Neonatal- caused by trauma from birth. Whatever part of the tooth was forming at the time of birth (considered a traumatic event) will hold and then continue on Owen- caused by hesitations seen in maturation stages of the dentin
50
When does tetracycline staining occur?
When taking tetracycline while tooth growth is occurring
51
What is tertiary dentin (aka reparative dentin)?
Dentin deposited by newly differentiated odontoblasts at the site of pulpal trauma
52
What is tertiary dentin a defensive reaction for?
To attempt to wall off the pulp from the site of injury (e.g., caries)
53
What happens when cells in the subodontoblastic layer are exposed to growth factors released by stimulated pulpal cells?
Differentiate and form the matrix of reparative dentin
54
What are growth factors that are released in the subodontoblastic layer that function as tertiary or reparative dentin?
* Bone Morphogenetic Protein (BMP) * Insulin-like Growth Factor (IGF) * Fibroblast Growth Factor (FGF) * Dentin Matrix Protein (DMP)
55
What is pulp capping?
Bridge of reparative dentin in root canal
56
What is dentinogenesis imperfecta?
- Hereditary defect that results in bluish-gray teeth with an opalescent sheen - The enamel is normal but chips off due to lack of support by the abnormal dentin - The pulp chamber and canals are generally obliterated by defective dentin formation
57
What happens in dentinogenesis imperfecta at the dentino-enamel junction?
Tubulin is missing = no support between dentin and enamel
58
What is attrition?
Loss by wear of surface caused by tooth to tooth contact during mastication or parafunction Due to bruxism
59
How can attrition be identified?
Matching wear on occluding surfaces, and shiny facets on amalgam contacts are common. Enamel and dentin wear is at the same rate. Possible fracture of cusps or restorations
60
What is another thing that dental attrition can be due to?
Bruxism (teeth become sensitive to cold)
61
What is erosion?
Loss of hard dental tissue by chemical processes
62
What does erosion look like?
Broad concavities, with cupping of occlusal surfaces and dentin exposure Incisal translucency as well as wear on non-occluding surfaces. Amalgam restorations appear “raised“ and have a non-tarnished appearance
63
Describe patients that have erosion
Patients are usually hypersensitive Very common with GERD patients
64
Many hydroxyapatite crystals exhibit a core of a relatively more
soluble carbonate apatite
65
The carbonate substitution in the lattice structure of enamel occurs primarily at
phosphate sites
66
The core of carbonated apatite is eroded preferentially by
acids due to its greater susceptibility to dissolution
67
_________ may substitute for hydroxyl ions in hydroxyapatite, conferring greater stability and resistance to acidic dissolution
Fluoride to stabilize hydroxyapatite core and make less susceptible to carries
68
Bacteria responsible for dental caries include:
Ø Streptococcus mutans (enamel/dentin caries) Ø Streptococcus sorbrinus (enamel/dentin caries) Ø Streptococcus gordonii (enamel/dentin caries) Ø Lactobacillus acidophilus (enamel/dentin caries) Ø Actinomyces viscosus (root caries)
69
Describe the spread of dental carries
***enamel -> dentin -> pulp*** Enamel: - A substantial cavitation is produced beneath the adjacent enamel surface - Initially, the caries lesion exhibits a small opening or orifice in the enamel and **pyramidal shaped** dentin lesion with the apex of the pyramid pointing towards the tooth pulp DEJ: - As the process of dental caries (acid dissolution of the enamel) reaches the DEJ, it **spreads laterally** (due to the branching of dentinal tubules at the DEJ) and then penetrates towards the pulp within the dentinal tubules Pulp: - pulp necrosis can occur due to overwhelming of the pulpal tissue with carious lesion
70
When do caries spread laterally?
After hitting DEJ because it is softer and more organic
71
What teeth are most commonly affected by dental sensitivity?
Cuspids and bicuspids aka canines and premolars
72
What are stimuli associated with dentinal sensitivity?
* Cold and/or hot beverages * Sweet or sour (acidic) foods or beverages * Overly aggressive brushing * Acidogenic plaque bacteria * Cosmetic bleaching of teeth * Clenching or bruxism
73
What activates and causes sensitivity?
Free nerve endings
74
What is the direct innervation theory?
Direct stimulation of nerve endings in dentinal tubules
75
What is the transduction theory?
Stimulation of odontoblasts that are coupled to nerves in the pulp
76
What is Brännström’s Hydrodynamic Theory?
Stimulation of dentinal tubules or exposed odontoblastic cell processes causes movement of tissue fluids within dentinal tubules that, in turn, stimulates nerve endings in close association with dentin at the dentin/pulpal interface
77
What is Charles' law?
The volume of a gas (or fluid) is directly proportional to the amount of heat applied at a constant pressure
78
Describe Charles law as it relates to dentistry
**If heat is applied** to tooth, the volume of fluid in the tubules **increases** (stimulates nerve endings) **If cold is applied**, the volume of fluid in the tubules **decreases** (stimulates nerve endings)

D1 Spring - Histopathology (14 decks)

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