Dentin/Pulp Complex Flashcards
what is pulp?
soft connective tissue in tooth center
blood vessels, whole cells
non- mineralized
what is dentin?
mineralized connective tissue covering pulp no blood vessels no whole cells odontoblast process nerve endings
what is the clinical significance of dentin?
quantitative
protective: both pulp and enamel
what is the importance of the dej?
scalloped in the crown- facilitates adhesion
what is dentinogenesis?
development of dentin
what stage does dentinogenesis begin in?
the bell stage
what are the conditions just prior to dentinogenesis?
tissue layers of dental organ present
crownoutline present
no odontoblast or ameloblasts
what happens in the late bell stage?
inner enamel epithelial cells-ameloblasts
undiffereentiated mesenchymal cells (dental papilla)-odontoblasts
dentin secreted
enamel secreted
how are odontoblast differentiated?
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
what are the inductive signals for odontoblast differentiation?
from enamel organ
most likely multiple signals
several families of signaling/growth factors implicated
one is Wnt10a
what is the process of dentin mineralization?
odontoblast secretes organic matrix and then the matrix is mineralized
what is predentin?
unmineralized organic matrix of dentin
what are the requirements for mineralization?
- calcium2+ and phosphate 2-
ca2+ from plasma
phosphate from plasma and cleavage of organic molecules containing phosphate
trasported into dentin through and between odontoblasts - initiation of crystal formationn
mantle and circumpulpal
what is mantle dentin?
first dentin laid down
how is mantle dentin formed?
- as odontoblast increase in size, they produce smaller collagen type 1 fibrils that orient themselves parallel to the future dej.
- 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.
formation of mantle dentin
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
how is circumpulpal dentin formed?
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
functional consequences of developmental differences between mantle and circumpulpal dentin
mantle dentin more organic-larger collagen fibers
mantle dentin less mienralized
dej vulnerable to caries
what is dentin phosphoprotein?
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
hardness of dentin
softer than enamel but harder than bone and cementum
how is the mineral phase of dentin organized?
random orientation
is dentin cystals smaller or largert than enamel crystals?
smaller
what is the organic phase of dentin?
processes of cells and extracellular matrix
what does the extracellular matrix contain?
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
what dentin dominant proteins consitutes 5-8% of noncollagenous proteins and what are their functions?
dentin matrix protein 1
dentinglycoprotein
dentin sialoprotein
functions unknown
what dentin dominant proteins constitutes more than 50 percent of non collageoneous proteins?
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
what mutations cause dentinogenesis imperfectain humans?
- changes in the 1st 3 amino acids
- small basepair deletions that produce frameshifts coding the part of the molecule that contain polar AA repeats; polar chnage to uncharged
what is the result of both types of mutations?
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
what are the contents of dentinal tubules?
fluid (major component= water) nerve fibers odontoblastic process small amount collagen fibers non-cellular lining sheath
what is the orientation of dentinal tubules?
at right angles to DEJ
s-shaped in crown
straighter in root
have terminal and lateral branches
tubule differences in dentin
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
primary dentin
dentin formed until completion of root development
comprises most of dentin
mantle dentin
20u-150u layer at DEJ
less mineralized
circumpulpal dentin
central to mantle dentin
more mineralized
secondary dentin
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
tertiary (reparative and reactive dentin)
produced in specific location in response to noxious stimulus
structurally irregular
may or may not have tubules
may include cells
intertubular vs intratubular/peritubular dentin
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
translucent or sclerotic dentin
tubules completely filled with intra/peritubular dentin
translucent- normal process of aging
sclerotic- accelerated deposition due to caries or attrition
dead tracts
tubules dry out; become filled with air
interglobular dentin
hypomineralized dentin just below mantle dentin- in crown
calcospherites
initial mineralization of dentin occurs in discrete foci
individual foci of calcification eventually fuse. if not interglobular dentin
tome’s granular layer
always in root of tooth
unmineralized dentinal tubules
what does growth lines in dentin reflect?
the incremental pattern of deposition
