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Oral Histology Exam 2 > Dentin/Pulp Complex > Flashcards

Dentin/Pulp Complex Flashcards

1
Q

what is pulp?

A

soft connective tissue in tooth center
blood vessels, whole cells
non- mineralized

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2
Q

what is dentin?

A 
mineralized connective tissue covering pulp
no blood vessels 
no whole cells
odontoblast process
nerve endings
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3
Q

what is the clinical significance of dentin?

A

quantitative

protective: both pulp and enamel

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4
Q

what is the importance of the dej?

A

scalloped in the crown- facilitates adhesion

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5
Q

what is dentinogenesis?

A

development of dentin

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6
Q

what stage does dentinogenesis begin in?

A

the bell stage

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7
Q

what are the conditions just prior to dentinogenesis?

A

tissue layers of dental organ present
crownoutline present
no odontoblast or ameloblasts

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8
Q

what happens in the late bell stage?

A

inner enamel epithelial cells-ameloblasts
undiffereentiated mesenchymal cells (dental papilla)-odontoblasts
dentin secreted
enamel secreted

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9
Q

how are odontoblast differentiated?

A

they elongate with nucleus moving to base of cell. as they grow, multiple processes are formed and dentin matrix secreted. odontoblast process elongate and one become dominant- that one lays down dentin

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10
Q

what are the inductive signals for odontoblast differentiation?

A

from enamel organ
most likely multiple signals
several families of signaling/growth factors implicated
one is Wnt10a

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11
Q

what is the process of dentin mineralization?

A

odontoblast secretes organic matrix and then the matrix is mineralized

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12
Q

what is predentin?

A

unmineralized organic matrix of dentin

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13
Q

what are the requirements for mineralization?

A
  1. calcium2+ and phosphate 2-
    ca2+ from plasma
    phosphate from plasma and cleavage of organic molecules containing phosphate
    trasported into dentin through and between odontoblasts
  2. initiation of crystal formationn
    mantle and circumpulpal
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14
Q

what is mantle dentin?

A

first dentin laid down

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15
Q

how is mantle dentin formed?

A
  1. as odontoblast increase in size, they produce smaller collagen type 1 fibrils that orient themselves parallel to the future dej.
  2. odontoblast form extracellular matrix, buds off a number of matrix vesicles that lies superficially near the basal lamina. vesicle contains annexin, alkaline phosphatase, calcium. - association of phosphate ions with intravesicular calcium results in formation of cyrsta;s/ odontoblast develops tomes fiber left behind. mineral phase first appears within the matrix vesicles as single crystals seeded by phospholipids of vesicle membrane. crystal grows.
    deposition of mineral lags behind the formation of organic matrix- predentin.
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16
Q

formation of mantle dentin

A

odontoblasts secrete matrix then matrix mineralizes
near end of mantle dentin formation, one process becomes dominant
odontoblasts migrating toward pulp center- dentin forms around process

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17
Q

how is circumpulpal dentin formed?

A

first type 1 collagen is secreted from odontoblastic cell body. fibrils are smaller and parallel to basal lamina
mineralization proteins are synthesized and secreted from odontoblastic process. proteins bind to collagen and their special properties precipitate ca2+ ions present in intersititial fluid and initiate crystal formation

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18
Q

functional consequences of developmental differences between mantle and circumpulpal dentin

A

mantle dentin more organic-larger collagen fibers
mantle dentin less mienralized
dej vulnerable to caries

19
Q

what is dentin phosphoprotein?

A

relatively specific to dentin
prominent dentinal protein- >50% of noncollagenous proteins
highly phosphorylated
high in serine/aspartic acid
acidic/anionic
hypothesized to precipitate ca2+ ions from tissue fluid, initiates mienralization

20
Q

hardness of dentin

A

softer than enamel but harder than bone and cementum

21
Q

how is the mineral phase of dentin organized?

A

random orientation

22
Q

is dentin cystals smaller or largert than enamel crystals?

A

smaller

23
Q

what is the organic phase of dentin?

A

processes of cells and extracellular matrix

24
Q

what does the extracellular matrix contain?

A

collagen and non collagenous proteins
type 1 collagen- 90% of organic matrix
non-tissue specific proteins- proteoglycans, signaling molecules and growth factors
mienralized-tissue specific proteins- osteocalcin, bone sialoprotein
dentin-dominant proteins

25
Q

what dentin dominant proteins consitutes 5-8% of noncollagenous proteins and what are their functions?

A

dentin matrix protein 1
dentinglycoprotein
dentin sialoprotein
functions unknown

26
Q

what dentin dominant proteins constitutes more than 50 percent of non collageoneous proteins?

A

dentin phosphoprotein (dpp) aka phosphryn
they are anionic- included long chain of polar amino acid repeats. more than 200 serine-serine-aspartic acid
serines are phosphorylated
gene DSPP cleaved to make DPP and DSP

27
Q

what mutations cause dentinogenesis imperfectain humans?

A
  1. changes in the 1st 3 amino acids
  2. small basepair deletions that produce frameshifts coding the part of the molecule that contain polar AA repeats; polar chnage to uncharged
28
Q

what is the result of both types of mutations?

A

abnormal DSPP cannot be released from the odontoblast. it is stuck in rER or cell membrane
mutated DSPP also traps the normal protein made by the unaffected chromosome
DI is a dominant negative mutation

29
Q

what are the contents of dentinal tubules?

A 
fluid (major component= water)
nerve fibers
odontoblastic process
small amount collagen fibers
non-cellular lining sheath
30
Q

what is the orientation of dentinal tubules?

A

at right angles to DEJ
s-shaped in crown
straighter in root
have terminal and lateral branches

31
Q

tubule differences in dentin

A

number of tubules in inner dentin is more than outer dentin
diameter of tubules is larger in inner dentin
tubules occupy less surface area at DEJ than at pulp-dentin border thus permeability and wetness increase toward pulp-dentin border

32
Q

primary dentin

A

dentin formed until completion of root development

comprises most of dentin

33
Q

mantle dentin

A

20u-150u layer at DEJ

less mineralized

34
Q

circumpulpal dentin

A

central to mantle dentin

more mineralized

35
Q

secondary dentin

A

dentin formed at root development
formed at slower rate but throughout life
central to primary dentin
similar to primary dentin in structure
also classified as circumpulpal dentin because its formed throughout life, the pulp chamber gets smaller with aging
secondary dentin is central to primary dentin and comprises a much smaller proportion of total dentin

36
Q

tertiary (reparative and reactive dentin)

A

produced in specific location in response to noxious stimulus
structurally irregular
may or may not have tubules
may include cells

37
Q

intertubular vs intratubular/peritubular dentin

A

intertubular- between tubules and intratubular/peritubular- lining tubules
both types found in primary and secondary dentin
intertubular dentin volume more than intratubular dentin
interatubular dentin more mineralized than intertubular
intratubular ring wider near dej- accounts for narrowing of tubule

38
Q

translucent or sclerotic dentin

A

tubules completely filled with intra/peritubular dentin
translucent- normal process of aging
sclerotic- accelerated deposition due to caries or attrition

39
Q

dead tracts

A

tubules dry out; become filled with air

40
Q

interglobular dentin

A

hypomineralized dentin just below mantle dentin- in crown

41
Q

calcospherites

A

initial mineralization of dentin occurs in discrete foci

individual foci of calcification eventually fuse. if not interglobular dentin

42
Q

tome’s granular layer

A

always in root of tooth

unmineralized dentinal tubules

43
Q

what does growth lines in dentin reflect?

A

the incremental pattern of deposition

Oral Histology Exam 2 (2 decks)

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