Dentin: Gross Structure and Composition Flashcards
T/F. Both pulp and dentin are connective tissues.
True
Which structure is mineralized connective tissue covering pulp with no blood vessels or whole cells? It does contain odontoblast processes and nerve endings.
dentin
Which structure is a soft connective tissue in the tooth center that is not mineralized and contains blood vessels and whole cells?
pulp
Where are the cell bodies for the nerve endings in dentin located?
trigeminal ganglion
What is the clinical significance of dentin?
- quantitative
2, protective of both the pulp and enamel
Which is harder, stiffer and has a higher compressive strength (flexible)?
Hardness = Enamel
Stiffness = Enamel
Compressive strength = Dentin
T/F. Enamel cushions the underlying dentin.
False, dentin cushions the overlying more brittle enamel.
T/F. Conditions that affect dentin also affect enamel.
True. Example, dentinogenesis imperfecta, enamel often splits.
The DEJ is ____ which facilitates adhesion and resist shearing forces during mastication.
scalloped
When does dentinogenesis begin?
during the Bell Stage
T/F. Just prior to dentinogenesis the tissue layers of the dental organ are present, the crown outline is present and there are no odontoblasts or ameloblasts.
True.
Dentinogenesis occurs from the ___ tips to the ___.
cusp; cervix
What are the four processes that occur during the late bell stage?
- inner enamel epithelial cells become ameloblasts
- undifferentiated mesenchymal cells (dental papilla) form odontoblasts
- dentin is secreted
- enamel is secreted
What two fates does the undifferentiated mesenchymal cells undergo?
- preodontoblasts
2. dental papilla/pulp
Initially the odontoblasts have many ____ that eventually decrease in number to 1-2. These cells secrete ___ ___ collagen into the matrix and as they move closer towards the pulp the matrix nearer the ___ ___ is mineralized.
processes; type 1; basal lamina
During the ___ bell stage, dentinogenesis is formed from the periphery to the ___ center.
late; pulp
___ signal for odontoblast differentiation is secreted from the enamel ___ at the site of the enamel ___. The major signaling/growth factors is ___.
Inductive; organ; knot; Wnt10a
What evidence suggests that there is a wave of odontoblast differentiation?
Wnt10a is first expressed in the enamel knot
Then in pre-odontoblast at the cusp tip
Then in successively more cervical parts of the teeth.
Adding Wnt10a induces ___ ___ (___), a molecule expressed by mature odontoblasts.
dentin sialophosphoprotein ( DSPP)
Odontoblast secrete an ___ matrix that is later mineralized.
organic
What is the name of unmineralized organic matrix of dentin?
predentin
What are the two requirements for mineralization?
- Ca+ and phosphate
2. initiation of crystal formation
___ comes from free ions in the plasma and ___ comes from plasma and the cleavage of organic molecules in odontoblast by ___ ___ enzyme.
Ca+; phosphate; alkaline phosphate
Where are Ca+ and phosphate transported to?
predentin through and between odontoblasts
The initiation of crystal formation involves the ___ (initial) and ___ (subsequent) stages.
mantle; circumpulpal
The mantle dentin formation is referring to dentin at the ___ and the principal component of organic matrix is ___ ___ ___. The mantle dentin is secreted by ___ and contains relatively large ___ oriented at ___ ___ to basal lamina/future DEJ.
DEJ; type 1 collagen; odontoblasts; fibrils; right angles
Mineralization of mantle dentin occurs in matrix ___ that are synthesized by ___.
vesicles; odontoblast
As the odontoblasts migrate toward the pulp center, what forms around the one process that dominates?
dentin
___ dentin formation occurs interior to mantle dentin. It is ___ but it’s overall process is similar - organic matrix is secreted then mineralized.
Cirucmpulpal; thicker
Where is type 1 collagen secreted during circumpulpal dentin formation?
the cell body (not the processes as in mantle dentin formation)
What is the size of circumpulpal dentin fibrils and how are they arranged?
small
parallel to basal lamina
T/F. Mineralization of circumpulpal dentin occurs via matrix vesicles.
False, it does NOT involve matrix vesicles
Which type of dentin contains non-collagenous proteins that are synthesized and secreted from odontoblasts processes?
circumpulpal dentin
Describe heterogeneous nucleation.
Proteins bind collagen and precipitate Ca+ ions present in interstitial fluid to initiate crystal formation.
T/F. Mantle dentin is less organic and more mineralized. The DEJ is vulnerable to caries.
False, Mantle dentin is MORE organic and LESS mineralized.
True, the DEJ is vulnerable to caries.
What molecule precipitates Ca+ ions from tissue fluid to initiate mineralization?
Phosphophoryn/Dentin phosphoprotein
Describe the properities of dentin phosphophoryn.
It is highly phosphoylated with high serine/apartic acid residues that make it acidic/anioinic (negatively charged).
___ is harder than bone and cementum but softer than ___. Why?
Dentin; enamel
Percentages of Hydroxyapatite (inorganic) content
Enamel 96%, Dentin 70%, Bone 50-60%, Cementum 45-50%
Dentin has ___% water by weight and ___% by volume, 20% organic by weight and ___% by volume, and ___% inorganic by weight and 45% by volume.
10; 22; 33; 70
What is found in the organic phase of dentin?
process of cells, ECM - collagen (type I), non-tissue specific proteins (signaling molecules/growth factors), mineralized tissue (ostocalcin, bone sialoprotein) and dentin dominant proteins.
Which dentin dominant protein makes up greater than 50% of non-collagenous proteins, is anionic, includes a long chain of polar aa repeats, has greater than 200 serine-serine-aspartic acid, and the serines are phosphorylated?
dentin phosphoprotein (DPP, aka phosphophoryn)
What gives rise to DPP?
DSPP
What can occurs if a patient is deficient in DSPP?
dentin forms improperly (dentinogensis imperfecta)
What are the two types of changes that occur in dentinogenesis imperfecta?
- changes in the 1st 3 aa (iso, pro, val) critical for trafficking DSPP through the rER
- Small base pair deletions produce frameshifts in the region of DPP that contain polar aa repeats (polar changes to uncharged - ser for ala)
Where does the DSPP remain if the two mutations occur?
stuck in the rER or in the cell membrane
What else does mutated DSPP do to normal protein?
It acts as a dominant negative, where the normal protein made by the unaffected chromosome is not working.
add fixed normal DNA and different mutant DSPP DNA. measure amount of DSPP released from the cells.
What do dental tubules contain?
fluid, nerve fibers, odontoblastic processes,
Dentinal tubules are at ___ ___ to the DEJ, ___-shaped in the crown and ___ in the root. It contains terminal and lateral branches.
right angles; S; straighter
Why are branches more prominent at the DEJ and DCJ?
Because baby odontoblast had numerous projections
Which has more tubules, inner or outer dentin?
inner
Where is the diameter of the tubule larger, inner or outer dentin?
inner
T/F. Tubules occupy much less surface area at the DEJ, than @ the pulp-dentin border.
True.
T/F. Permeability and wetness increases at the DEJ.
False, permeability and wetness increases toward the PULP-DENTIN border.
T/F. Tubules create a natural pathway for microorganisms.
True.
T/F. Predentin is mineralized dentin.
False, predentin is unmineralized.
What type of dentin is formed until completion of root development and comprises most of the dentin?
primary dentin
mantle dentin (less mineralized) - 20u-150u layer @ DEJ circumpulpal dentin (more mineralized) - central to mantle
Which type of dentin is formed after root development?
secondary dentin
T/F. Secondary dentin is formed at a slower rate but throughout life.
True, because it is formed throughout life, the pulpal chamber gets smaller with aging.
Secondary dentin is located ___ to primary dentin (closer to the pulp), is similar in structure and presents along the entire circumference of the ___ ___, but heaviest on the roof and floor.
central; pulp chamber
What is another name for teritary dentin?
reparative or reactive dentin
Which type of dentin is produced in a specific location in response to noxious stimulus in a structurally irregular fashion?
tertiary dentin
T/F. Secondary dentin is central to primary dentin and comprises a much SMALLER proportion of total dentin.
True.
T/F. Intertubular and intratubular/peritubular dentin is found only in primary dentin.
False, Intertubular and intratubular/peritubular dentin is found in BOTH primary and secondary dentin.
Which has more volume, intertubular or intratubular dentin?
inTERtubular
Which is more mineralized, intertubular or intratubular?
inTRAtubular
The ___ denin’s ring is wider near the DEJ. This accounts for narrowing of the tubule.
inTRAtubular
What type of dentin has tubules completely filled with inTRA/peritubular dentin that is a normal process of aging?
translucent
___ dentin is an accelerated deposition due to caries or attrition.
Sclerotic
What term is used to describe tubules that are dried out and become filled with air?
dead tracts
What term is used to describe hypomineralized dentin just below mantle dentin?
interglobular dentin
Initial ___ of dentin occurs in discrete foci of calicificaiton, ___, that eventually fuse. If they don’t it is known as ___ dentin.
mineralization; calcospherites; interglobular
T/F. There is much interglobular dentin in DSPP knockout mice.
True.
What term is used to decribe hypomineralized areas in the root of the tooth?
Tome’s granular layer
___ lines in dentin reflect the incremental pattern of deposition. Pronounced lines can occur that reflect perturbations. Examples include ___ lines commonly observed in teeth mineralizing at birth and exaggerated lines seen due to ___ treatment.
Growth; neonatal; tetracycline
