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Oral Histology > Dentin > Flashcards

Dentin Flashcards

1
Q

dentin and pulp have an intimate relationship, but they are distinctive. HOW?

A

pulp is a non-mineralized soft connective tissue that is covered by the mineralized CT (dentin)

  • pulp has blood vessels and whole cells whereas dentin doesn’t have blood vessels or whole cells (OB processes and nerve endings)
  • *pulp makes the dentin
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2
Q

where are the cell bodies that have their processes in the pulp and dentin

A

cell bodies from the trigeminal nerve

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3
Q

how does dentin protect both enamel and pulp?

A

covers soft tissue (pulp) and acts a shock absorber for enamel brittle enamel because dentin’s compressive strength (flexibility) is greater than enamel

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4
Q

can defects in dentin affect enamel?

A

yes

ex. dentinogenesis imperfecta

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5
Q

why is DEJ scalloped in the crown?

A

** dentin has finger like projections that extend into the enamel for adhesion

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6
Q

where does dentinogenesis begin?

A

begins during the “bell stage”

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7
Q

what do the tissues look like prior to dentinogenesis

A

prior to dentinogenesis the tissue layers of the enamel organ are present, the outline of the crown is present
**there are NO odontoblasts or ameloblasts

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8
Q

what direction does dentinogenesis occur?

A

cusp tips to cervix and periphery to pulp center

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9
Q

explain the how the periphery of the dental papilla cells differentiate into ODB

A

first the pre-AB start changing and becoming columnar cells (telling the mesenchyme cells to stop dividing). The enamel knot (concentration of epithelial cells in the enamel cap) secretes a signal that allows for the undifferentiated mesenchymal cells to differentiate into ODB

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10
Q

what happens to the 2 daughter cells of the pre-odontoblasts?

A

one becomes fibroblast and the other goes to pulp (to be ODB)

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11
Q

what molecular family is said to be a signaling molecule secreted by enamel knot?

A 
Wnt family (specifically Wnt10a)
**expression of Wnt10a immediately proceeds the wave of odotoblast differentiation
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12
Q

what experiment proves that wnt10a induces ODB differentiation?

A

embyonic mesoderm cells subject to wnt10a express Dspp (dentin sialophosphoprotein is expressed by mature ODB)

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13
Q

when dentin is secreted is is mineralized?

A

NO

unmineralized predentin is first

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14
Q

what are the requirements for mineralization?

A
  1. Ca and Ph (from free ions in plasma and cut from organic molecules with alkaline phosphatase) that are transported through or btwn ODB in unmineralized matrix
  2. initiation of crystal formation (energy process) either through mantle or circumpulpal dentin formation
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15
Q

what is the principal component of the organic matrix of dentin?

A

collagen type I fibers

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16
Q

where is mantle dentin formation

A

at the DEJ (first layer of dentin)

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17
Q

how is mantle dentin mineralized?

A

through matrix vesicles that are synthesized by ODB taking in lots of calcium and Ph through binding proteins where they form crystals (in matrix) burst and then mineralize the LARGE collagen fibers secreted by ODB at RIGHT ANGLES to the basal lamina (aka DEJ)

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18
Q

what causes the vesicles to mineralize?

A

special proteins inside or just a really high number of Ca ions

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19
Q

how does circumpulpal dentin formation occur?

A

the ODB grows towards pulp center, process elongates (until there is only 1) and dentin forms around the processes. Smaller collagen fibrils parallel to basal lamina (DEJ) secreted by ODB cell body and mineralized by PROTEINS (not matrix vesicles) in the ODB processes

20
Q

how do the proteins cause mineralization in circumpulpal dentin?

A

special properties allow Ca to percipitate out in the interstitial fluid t allow crystalization
**heterogeneous nucleation

21
Q

what are the diff (functionally) in the circumpulpal vs. mantle dentin?

A

mantle is more organic (more collagen) so softer and less mineralized which means the DEJ is more susceptible to caries

22
Q

dentin phosphoprotein/ phosphoryn

A
  • (relatively) specific to dentin (small amounts elsewhere)
  • most prominent dentinal protein (>50% non-collagenous proteins)
  • highly phosporylated (anionic)
  • high in serine/aspartic acid
  • secreted by ODB
  • **protein that causes the circumpulpal dentin to mineralize through precipitating (pulling out) calcium ions out of tissue fluid
  • comes from gene is DSPP (dentin sialophosphoprotein)
23
Q

what percent of dentin is HA?

A

70%

24
Q

what is the difference in enamel vs. dentin HA crystals?

A

enamel is larger, more mineralized, harder and more orderly

** dentin is random

25
Q

what are parts of the organic phase of dentin

A
  • cell processes and ECM
  • the ECM is 90% type 1 collagen but the non-collagenous proteins are non-tissue specific (ex. growth/signaling factors like bone morphogenic proteins and proteoglycans), mineralized-tissue specific (osteocalcin and bone sialoprotein) and dentin-dominant proteins
26
Q

what are the dentin dominant proteins?

A

dentin matrix protein 1, dentin glycoprotein, dentin sialoprotein

27
Q

when there is no DSPP what happens?

A

hypomineralization of dentin (ex. dentinogenesis imperfecta because dentin doesn’t form properly)
**hard to tell on knockout DSPP mouse if DPP is the cause for hypomineralization because makes DGP and DSP too

28
Q

what are the 2 mutations in humans (not in mice) that lead to DI?

A
  1. changing the first 3 aa that are needed to move DSPP out of the RER (can’t leave rer is mutated)
  2. base pair deletion leading to the polar molecule to become uncharged (cant leave cell membrane is mutated)
29
Q

why is DI a dominant negative in humans?

A

because the more abnormal DSPP there is, then more normal DSPP (from normal chromosome) is trapped to decrease its release

30
Q

dentinal tubules content

A

fluid (water), nerve fibers, ODB processes, collagen fibers and non-cellular lining sheath???

31
Q

why are tubules straighter in the root then the crown (s shape)?

A

because ODB crowding moving into pulp chamber

32
Q

what angle are the dentinal tubules at?

A

right angle to DEJ

33
Q

where are the terminal and lateral branches of the dentinal tubules?

A

DEJ and DCJ

34
Q

why are br. more prominent at the DEJ and DCJ?

A

because thats where odontoblasts first “form” and baby ODB have many processes that extend out towards the junctions and as they progress down the ECM takes up the place of the processes (not as visible)

35
Q

difference in tubules btwn the inner and outer dentin

A

inner dentin has more tubules with a larger diameter than the outer dentin (larger to get to “wet” pulp”)
**less surface area occupied at the DEJ by tubules than at the P-D border

36
Q

primary dentin

A

until completion of root development

**most of dentin (mantle and circumpulpal)

37
Q

what is the diameter of mantle dentin?

A

20-150 under layer at DEJ

38
Q

secondary dentin

A
  • formed after rt development
  • slower rate but throughout life
  • central to primary dentin
  • all along the pulp chamber, but heaviest on the roof and floor
  • *circumpulpal dentin as well
  • looks like primary dentin
39
Q

tertiary (reparative and reactive dentin)

A

-produced in a specific location due to noxious stimulus (caries or attrition)
-irregular structure (may not have tubules (look like bone), may include whole cells?)
reactive - mild stimulus
reparative - caries kill ODB

40
Q

intertubular vs. intratubular/peritubular dentin

A

intertubular dentin is between and intratubular dentin lines the tubules
-found in primary and secondary dentin
intertubular&raquo_space; intratubular
intratubular is more mineralized than intertubular

41
Q

what accounts for the narrowing of the tubules near the DEJ?

A

intratubular ring becoming wider

  • *may even occlude the tubules near the DEJ (so fewer tubules)
  • **** all of the dentin we talked about as far as formation (mantle and circumpulpal) is intertubular dentin
42
Q

translucent/sclerotic dentin

A
  • tubules filled with intra/peritubular dentin
  • *both increase with age
  • translucent is the normal aging process and sclerotic is because there is accelerated deposition due to caries
  • *makes the tooth harder and more caries resistant
43
Q

dead tracts

A

tubules that dry out and fill with air

44
Q

interglobular dentin

A

individual foci are mineralized first (calcospherites) which will fuse to mineralize. If they do not fuse, then interglobular dentin forms
**a lot in DSPP knockout mice

45
Q

Tome’s granular layer

A

looped temrinal br. tubules (looks like sand) always in outer dentin in the root of the tooth ( near the DCJ)

46
Q

growth lines in dentin

A

pronounced growth lines can occur that reflect perturbations ex. is neonatal line observed in teeth mineralizing at birth
** growth lines are exaggerated due to tetracycline treatment by mother because it binds to collagen fibers

Oral Histology (13 decks)

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