Dentin/Pulp Complex

Question 1

what is pulp?

Answer 1

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

Question 2

what is dentin?

Answer 2

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

Question 3

what is the clinical significance of dentin?

Answer 3

quantitative

protective: both pulp and enamel

Question 4

what is the importance of the dej?

Answer 4

scalloped in the crown- facilitates adhesion

Question 5

what is dentinogenesis?

Answer 5

development of dentin

Question 6

what stage does dentinogenesis begin in?

Answer 6

the bell stage

Question 7

what are the conditions just prior to dentinogenesis?

Answer 7

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

Question 8

what happens in the late bell stage?

Answer 8

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

Question 9

how are odontoblast differentiated?

Answer 9

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

Question 10

what are the inductive signals for odontoblast differentiation?

Answer 10

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

Question 11

what is the process of dentin mineralization?

Answer 11

odontoblast secretes organic matrix and then the matrix is mineralized

Question 12

what is predentin?

Answer 12

unmineralized organic matrix of dentin

Question 13

what are the requirements for mineralization?

Answer 13

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

Question 14

what is mantle dentin?

Answer 14

first dentin laid down

Question 15

how is mantle dentin formed?

Answer 15

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.

Question 16

formation of mantle dentin

Answer 16

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

Question 17

how is circumpulpal dentin formed?

Answer 17

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

Question 18

functional consequences of developmental differences between mantle and circumpulpal dentin

Answer 18

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

Question 19

what is dentin phosphoprotein?

Answer 19

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

Question 20

hardness of dentin

Answer 20

softer than enamel but harder than bone and cementum

Question 21

how is the mineral phase of dentin organized?

Answer 21

random orientation

Question 22

is dentin cystals smaller or largert than enamel crystals?

Answer 22

smaller

Question 23

what is the organic phase of dentin?

Answer 23

processes of cells and extracellular matrix

Question 24

what does the extracellular matrix contain?

Answer 24

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

Question 25

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

Answer 25

dentin matrix protein 1 dentinglycoprotein dentin sialoprotein functions unknown

Question 26

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

Answer 26

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

Question 27

what mutations cause dentinogenesis imperfectain humans?

Answer 27

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

Question 28

what is the result of both types of mutations?

Answer 28

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

Question 29

what are the contents of dentinal tubules?

Answer 29

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

Question 30

what is the orientation of dentinal tubules?

Answer 30

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

Question 31

tubule differences in dentin

Answer 31

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

Question 32

primary dentin

Answer 32

dentin formed until completion of root development | comprises most of dentin

Question 33

mantle dentin

Answer 33

20u-150u layer at DEJ | less mineralized

Question 34

circumpulpal dentin

Answer 34

central to mantle dentin | more mineralized

Question 35

secondary dentin

Answer 35

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

Question 36

tertiary (reparative and reactive dentin)

Answer 36

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

Question 37

intertubular vs intratubular/peritubular dentin

Answer 37

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

Question 38

translucent or sclerotic dentin

Answer 38

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

Question 39

dead tracts

Answer 39

tubules dry out; become filled with air

Question 40

interglobular dentin

Answer 40

hypomineralized dentin just below mantle dentin- in crown

Question 41

calcospherites

Answer 41

initial mineralization of dentin occurs in discrete foci | individual foci of calcification eventually fuse. if not interglobular dentin

Question 42

tome's granular layer

Answer 42

always in root of tooth | unmineralized dentinal tubules

Question 43

what does growth lines in dentin reflect?

Answer 43

the incremental pattern of deposition