ex2. dentin/pulp complex 1 Flashcards
Is dentin cellular (contains whole cells) or acellular (does not contain whole cells)
Dentin is ACELLULAR.
Does the pulp or the dentin have nerve endings?
BOTH the pulp and the dentin contain nerve endings. Nerve endings penetrate up to 1/3 inner dentin.. and jus inside the pulp border (next door to odontoblast layer) is Rashkow’s plexus that is super rich in nerve endings (in the pulp)
how is dentin protective of the pulp AND enamel?
The dentin is located bt the enamel (supr) and pulp (deep). The dentin is a mineralized barrier that protects the pulp (like a shield).. however, the dentin also protects its superficial layer, the even harder Enamel. Dentin protects enamel by providing it with a cushy underlayer, so that the brittle enamel has some flex and cushion support and willnot crack so easily.
– if dentinforms imrpoperly (such as via dentinogeneisis imperfecta, a condition ) .the enamel is also impacted – it splits
T/F The DEJ (dentinoenamel junction) is described as being “scalloped”
True. The border bt the enamel and dentin is “scalloped” – which describes the shape of the interface bt the 2 layers. The wavy/scalloped border improves adhesion bt the 2 layers (which are mechanically retained.. not chemically or adhesively..)
In what stage of development of hte tooth germ does dentinogenesis (crown) begin?
Dentingenesis (crown) begins in the eptithelial bell stage of hte enamel organ, during toth germ development. ((recall – the nerve first enters the dental papilla during the epithelial bell stage as well)) //
just before dentinogenesis begins, there are no ameloblasts or odontoblasts present.
T/F The crown outline of the tooth is not visible just prior to dentinogenesis
False. Just prior to dentinogenesis (occurs in eptelial bell stage of the enamel organ), the Crown outline IS present in the enamel organ
T/F By the time dentinogenesis begins, there are plenty of ameloblasts and odontoblasts already formed.
False! Just prior to dentinogenesis, there are NO ameloblasts nor odontoblasts present. They form AFTER dentinogenesis begins (which is in the epithelial bell stage of enamel organ/ tooth germ development)
During which stage of odontogenesis do the ameloblasts and odontoblasts form?
The ameloblasts and odontoblasts form during the late portion of hte epithelial bell stage == the late bell stage.
recall, the ameloblasts derive from the inner epithlial layer of the enamel orgna (the coast of the bay) , and the odontoblasts form from undifferentiated mesenchymal cells
During which stage of odontogenesis does the enamel and dentin first start being secreted?
The enamel and dentin (recall- reciprocal induction!) are first secreted in the late bell stage (late part of hte epithlial bell stage of the enamel organ)) – this is the same stage (just after) the ameloblasts and odontoblasts form (the formative cells of enamel and dentin)
What is the general progrssion of dentingenesis? (where does it start and where does it finish?)
Dentinogenesis starts in the cusp tips (supr most of hte coronal area) and progresses apically/cervically to end in the cervix (cervical most extent of the developing dentin layer) AND proceeds from the periphery to the pulp center
What is Wnt10a?
Wnt10a is a signaling/ growth factor that triggers odontoblast diferntiation (from undifferentiated mesenchymal cells) .. Wnt10 expression has been tracked to follow the progeression of dentin formation - - aka they are related.
T/F The enamel organ inductively signals for odontoblast differntiation
True. The eputhelium of hte enamel organ and the ectomesenchyme are involed in reciprocal induction where one-another spur their development
ex// ameloblasts>odontoblasts>dentin>enamel..
it is true that the enamel organ inductively signals the odontoblast to differntiate (to the dentin formeing odontoblasts from the undifferentiated mesencymal cells)
T/F Wnt10a is the sole signal that triggers the start of dentinogenesis
False. Wnt10a is one of the Multiple signals that is indicated with the start and progress of dentinogenesis
Name two signalling molecules that are involved in dentinogenesis
Both Wnt10a and DSPP (dentin-specific marker) are involved in dentinogenesis
T/F Wnt10a induces DSPP?
True. Wnt10a (signal from ameloblasts) Induces DSPP (dentin-specific marker from odontoblasts) .. reciprocal induction bt mesenchyme and peithlium of the tooth germ
T/F The odontoblast secretion is mineralized upon secretion- just like enamel
False. The odontoblast secretion starts out organic (called predentin- lacking mineral salts.. nonmineralized) and is later mineralized. The odontoblast lays down the organic matrix in layers. Each layer is layed down, mineralzes,, ten another layer, mineralized..then another organic layer ((and mineralzied = inorganic)
*Further:: All mineralized tissues except enamel have a pre-mineralzied stage… only enamel is minerlaized immediately upon secretion (recall, the rodless layers are fully minerlazied imediately, whereas the rod and interrod substances are paritally minerlaized and then fully mineralzied… but all stages of ameloblast secretions ((except the last basal lamina layer)) are mineralized
What is the unmineralzied layer of dentin called?
The initial unmineralized dentin is called PREDENTIN
T/F All 3 components of the tooth germ are vascularized
False. The dental follicle (periodoontla ligament) and the dental papilla (pulp) are vasucalrized.. the 3rd part, the enamel organ, is AVASCULAR
Calcium and phosphate are both necessary for mineralziation.. from where are these materials gathered during odontogenesis?
calcium and phosphate are both attained from the blood plasma (the liquid portion of the blood)
- also,phosphate is also obtained from the cleavage of organic molecules.
- the phosphate and calcuym are tranported into the dentin through and bt the odontoblasts (tight junctions can permit small molecules passage)
T/F mantle and circumpulpal are the two locations/stages where dentin develops
True. The dentin develops in the mantle – which is the area of the DEJ, the mantle crystals/collagen form perpendicular to the DEJ (perpendicular/at a right angle to the layer outline) .
- then there is the odontoblast layer..
- then the circumpulpal layer is secreted by the odb (odonotoblast) cell body .. the collagen lies parallel to the basal lamina/ (parallel to layer outline)
Is there collagen in dentin?
Yes. Dentin contains collagen – mostly Type 1 collagen that is assoc with harder tissues
What is the major mineral of dentin that confers dentin its hardness?
The major mineral of dentin is hydroxyapatite (the same mineral as in enamel – but a lesser concetration)
Are the collagens of hte mantle and circumpulpal dentin the same ?
Not exactly. Both the mantle and the cirucmpulpal dentin have type 1 collagen.
some differences:
mantle collagen has LARGER collagenfibrils than circumpulpal fibrils (smaller than mantle fibrils)
** fibrils = (collagen fiber bundles)
“mineralization via matrix vesicles” describes what?
The mantle dentin mineralizes via matrix vesicles
Describe the mineralization process of matrix vesicles.. how do they promote crystal formation?
Matirx vesicles are mineralized, membrane-bound vesicles that take up calcium (a necessary compoennt of minerlaization) via annexin prtn.
Alkaline phosphate is in mineralzied tissues, and therefore in the matrix vesicles.. (phostate is a second necessar compoennt to minerlaization) .. a cleaving enz., alkaline phosphatase, breaks downt he alklaine phosphate to release the phosphate..
– the vesicle concetrates the calcium and the phosphate.. the concentration of these materials is suffieicient to promote crystalization. the vesciles go into the dentin matrix.. as crystals form, the vesicles burst releasing them, and the crystals continue to coalesce. ==ps, these crystals are the hydroxyapatite crytals HA. (Ca5(PO4)3(OH) hydroxyapatite
Recall, dentin formation occurs from periphery and coronal, to deep and cervical. The odontoblasts migrate towards the pulp center as they secrete organic matrix.. From where is the matrix secreted– the cell body or the process?
The organic matrix (predentin ) is secreted by the odontoblast as it migrates towards the pulpal cener, is secreted from the odontoblast PROCESS.
at first, there are severeal porcesses per odontoblast.. but as the mantle dentin forms, ONe process becomes dominant
T/F odontoblast processes are confined to only the dentin
False. The odontoblast processes are mostly in the dentin.. but the processes can cross the DEJ and extend into the enamel = is called an enamel spindle. since this enamel spindle is made out of dentin, it is hypominerlaized (less mineral compred to enamel).. and an entry point for caries into hte deeper dentin layers (and dentin more susceptible to acid than enamel. so a weak spot in the the enamel layer)
T/F The odontoblast has one main, dominant process
True. The odontoblast starts with several arms/ processes.. but as it migrates towards the pulp center,one process becomes dominant
Does the circumpulpal dentin form via matrix vesicles?
No, circumpulpal dentin does Not form via matrix vescles. (the mantle dentin DID form via matrix vescles.. recall– membrane bound, concetrated P and Ca into HA crystals..))
circumpulpal dentin is formed via proteins (such as phosphoryn) synth and secreted by odb processes
How is the collagen of the circumpulpal dentin differnt than the collagen of the mantle dentin?
The cirucmpulpal collagen is in smaller fibrls than mantle collagen. Both mantle and cirucmpulpal are tpe collagen (type 1collagen = assoc w harder tissues)
– the collagen of the circumpulpal dentin is oriented PARALLEL to the basal lamina (border shape at DEJ)
How does the dentin in the circumpulpal region mineralzie? Describe.
The dentin of the circumpulpal region mineralzies via proteins that are synthesized and secreted by odontoblasts processes. These prtns function to bind to collagen (at their GAP regions).. the proteins’ properties act to precipitate Calcium ++ ions present in the interstitial fluid and initiate crystal formation (crystla process= ‘heterogenous nucleation’)
Which of the dentin layers is more susceptible to caries?
The 2 dentin layers are the mantle and the circumpulpal dentin. The mantle, which is at the DEJ, is more susceptible to caries.
the mantle dentin is more susceptible to caries bc is it less mineralized (and more organic) than the circumpulpal dentin. ..
- the mantle dentin is less minerlaized due to its formation difference from the circumpulpal.. circumpulpa;l = Ca and P concetration via proteins.. the mantle however via matrix vesicle… matrix vescle mineralziation is more haphazard, plus the occurence of enamel spindles (odb/dentin process sextension into the enamel = hypominerlaized) = makes the dentin at the DEJ very susceptible to caries ((and seen in clinic.. think the inverted triangle progression of caries from enamel to dentin explosion))
T/F phosphoryn is a protein found throughout the body
False. phosphoryn/ aka dentin phosphoprotein is a tissue-specifc prtn, specific to dentin. This is the protein synthesized and secreted by the odontoblasts in the circumpulpal dentin. (((note, trace amts phosphoryn are in bone, cementum, and enamel))))
Phosphoryn contains a LOT of PHosphate… Phosphoryn prtn acts to precipiate ca++ , and then the phosphate of the prtn and the uptaken/precipitated calcium start to mineralize (hertorgenous nucleation) .. to form the HA, hydroxyapatite crytals that are fomred from calcium and phostaphate and give the mineralized tooth tissues their hardness
== heterogenous nucleation = It is the initial process in crystallization. Nucleation is the extremely localized budding of a distinct thermodynamic phase. It is the process in which ions, atoms, or molecules arrange themselves in a pattern characteristic of a crystalline solid, forming a site in which additional particles deposit as the crystal grows
Define heterogenous nucleation and where is it seen?
Heterogenous nucleation is seen in the circumpulpal dentin as it minerlaizes
defined:
It is the initial process in crystallization. Nucleation is the extremely localized budding of a distinct thermodynamic phase. It is the process in which ions, atoms, or molecules arrange themselves in a pattern characteristic of a crystalline solid, forming a site in which additional particles deposit as the crystal grows
What is the name of the molecule being described?
- mostly specific to dentin (trace amts exist in ohter minerlaized tooth tissues + bone)
- is highly phosphorylated
- is acidic/ anionic
- is high in serine/apartic acid
Being:
-mostly specific to dentin (has trace amts in enamel, cementu, nad bone), highly phosphorylated, acidic/anionic nature, and high in serine/apartic acid,
in addtion ot being a prminent dentin protein are all descriptive of phsophoryn, a tissue specific prtn of dentin that is synthesized and secreted by the obd processes
What is the percentage of hydrozyapatite (inorganic) content in dentin? The other minerlaized tissues?
Dentin contains 70% (by wt) HA hysdroxyapatite. detnin is the 2nd hardest tissue of the body.
Enamel = 96% dentin = 70% bone = 50-60% cementum= 45-50% hydroxyapatite, Ca5(PO4)3(OH) , by weight
Which tissue is more stiff0 enamel or dentin?
Enamel is a lot more stiff than dentin. Dentin acts as a cushion for the stiffer, harder enamel helping prevent splitting/fractures of the enamel via absorption of impact/flex.
enamel= 131 vs dentin = 12 (young’s modulus, GN/m^2) giganewtons= N x 10^9)
Which tissue has greater compressive strength- enamel or dentin?
Dentin has a much greater compressive strength than does enamel. enamel is harder and stiffer, dentin has fluid, is more cushy than enamel.
dentin = 262 vs enamel = 76 (MN/m^2) MN= meganewton’s N x 10^6
When looking at a radiograph.. is the mantle of the dentin more radiolucent, rdioopaque, or the same as its surrounding layers?
The mantle dentin is flanked by enamel on one side (coronal) and the odontoblasts on the other (pulpal).. the mantle is formed by a process (matrix vesciles minerlaization) that renders it less mineralized than the circumpulpal dentin (and it is naturally less minerlaized than enamel). as such, the mantle is visibile as a distinct entitiy on radiographs where it appears are a more radiolucent structure
lack of the DSPP (dentin specific protein) is associated with what condition?
DSPP is critical for dentin formation (induced in odb by the ameloblasts..) ..without DSPP< dentin does not mineralize properly.. and the condition is called DENTINOGENESIS IMPERFECTA.
Is the DSPP mutation dominantly or recessively inherited in humans?
the DSPP mutation (where DSPP is not functioning) is DOMINANTLY inherited (so one faulty copy = DSPP mutation in offspring..)) a DSPP mutation will lead to the dentinogeneiss imperfecta condition.
T/F There are 2 types of DSPP mutations that are known to cause dentinogenesis imperfecta in humans
True. There are 2 types of DSPP mutations that cause dentinogeneisi imperfecta in humans.
- a mutation in the first 3 aa of the DSPP seuqnece (should be iso, pro, val..)
- a frameshift that causes the prtn to become UNcharged. ((and no longer serine dominated.. should be high in serine concetration))
the result of both of these mutations is that DSPP cannot be released from the odontoblast – it is stuck in the rER
how is DSPP function disrupted by the 2 mutations that lead to denitnogeneiss imperfecta?
((** DSPP gene = codes for phosphoryn aka dentin phosphoprtn, DPP – leads to minerlaization of circumpulpal dentin))) Two different DSPP mutations lead to DSPP’s inability to be released from the rER of hte odontoblast. As such, DSPP is stuck and cannot fucntion normally.. this leads to D.I (( the normal chromosome makes normal DSPP prtn- the phosphoryn.. but the deficinet gene makes defiicient phosphryn that GUMPs up the exits and normal dspp cannot excape rER… as such,m DSPP mutations = dominant begative mutation))
how is the HA crystal formation of dentin different from enamel HA crystals?
The crystals is enamel are organized and neatly oriented in rods. The crystals of dentin are randomly oriented .
Describe the composistion of a hydrozyapatite crystal:
A hydroxyapatite unit cell has hte formula: Ca10 (PO4)6(OH)2 .. there are 1000s of these unit cells PER crystal.. .. byu comparision, enamel crystals are MUCH larger (looks like 2-4x+ bigger..))
90% of the organic extracellular matrix of the dentin is made up of what?
90% of the organic phase of dentin (the extracellular matrix) is made up of TYPE 1 COLLAGEN.
T/F the 3 basic categories of proteins found in denitn include:
non-(tissue) speicifc proteins
minerlaized tissue speicf proteins
and dentin dominant proteins
True. There are 3 main categores of proteins that are found in the dentin
- non-(tissue) specific proteins (this inc, proteoglycans, signaling molecules/ growth factors)
- mineralized-tissue speicifc protens = osteoclacin, and bone sialoprotn
- dentin dominant rptns (inc, dentin matrix prtn 1, dentin glycoprtn, dentin sialoprtn, dentin phosphoprtn (phosphoryn)
What is the most dominant amino acid found in phosphoryn?
Phosphoryn is dominated by serine amino acids .. the serines are phosphorylated (and this contributes to the minerlazation process of the circumpulpal dentin.. heterogenous nucleation “”). one of the 2 mutations schemes of phosphoryn ((via the DSPP gene)) is due to a frameshift eliminating the serine dominance
DSPP mutations are dominant, negative mutations.. but normal DSPP gene product is still formed.. explain
DSPP gene mutations are dominant. If one chromosome has faulty DSPP gnee, then faulty DPP (DSPP genen rpoduct) = phosphryn is produced.. The normal DSPP gene is able to make regular phoshryn.. but since one gene is malfuntioning, only haf the regular amt of DSPP is made, FURTHER< hte faulty phosphryn clogs up the exit ways and the normal phosphryn in treapped (along with deficient) inside the rER
T/F The only contents of dentinal tubules are dentin rods and nerves
False. Dentinal tubules contain FLUID, nerve fibers, and the odontoblast process, and some collagen fibers
- the fluid component is mostly water and some ions- it is a distilate of plasma
T/F The dentinal tubules are straight channels
False. The dentinal tubules are “s” shaped near the dentinal crown, though the tubules are straighter in the root. ** The dentinal tubules are arranged PERPENDICULAR to the DEJ
T/F The dentinal tubules are oriented parallel to the surface of the dentinal outline
False. THe dentinal tubules are oriented PERPENDICULAR to the DEJ
Is there any branching of dentin tubules?
YEs. DEntin tubules do exhibit branching (not very complex)
T/F The diameter of dentin tubules of the inner dentin is larger than the diameter of outer dentin tubules.
True. The inner dentin tubules are larger than the diameter of out dentin tubules
T/F The number of tubules is the same throughout the different areas of the dentin
False. The inner dentin has more dentin tubules than the outer dentin
(the inner dentin has tubules of larger diameter, too)
– these factors have important clinical manifestations (larger tubules..the dentin is increasingly wet as go deeper- and therefore more permeable ((entry of caries, etc))
Where is the dentin do the dentinal tubules have an “S” shape?
The dentin tubules have an “S” shape near the crown
CHOOSE:
The dentin tubules occupy:(( more/less/the same)) :surface area at the DEJ compared to the dentinopulpal border
The dentin tubules occupy LESS surface area at the DEJ compared to the dentinopulpal border
:significance: the deeper dentin with more and larger tubules is more wet and permeable – an easy pathway for microorganisms
T/F The dentin is less permeable but more wet towards the dentinopulpal border than at its coronal (superficial) surface
False. The dentin is both More Permeable and More wet at the dentinopulpal border than anywhere else
– this is bc the dentin tubules are more numerous and bigger diamter at the DP border. The tubules contain fluid as a major part of contents.. CLINICALLY, these permeable and wet tubules are easy pathways for microorganisms to enter the body
T/F Dentin does not form throughout our lives
False. Dentin DOES form throughout our lives. Dentin is layed down and mineralized in layers, and there are a few differnt types of dentin
predentin, primary, secondary, teritiary (reparative and reactive)
what are the different types of dentin
The differenty types of dentin are:
predentin, primary, secondary, teritary (reparative and reactive) dentins
-predentin– not yet mineralzied .. since dentin is laid down through life, there is always a layer of predentin (stains lighter than mineralzied)
- primary – forms during the time span up to when the root completes development
- secondary – dentin formed after root development is complete. located centrally(deep) to primary detnin
- teritary – there are 2 types reparative and reactive. both types respond to a noxious stimulus, and both types produce irregular dentin (such as w/w/o tubules)
- reparative: made by replacement odb/
- reactive: made by origninal obd
T/F All dentin has dentin tubules
Mostly true, but ultimately false.
Tertiary dentin can be irregular and may not have tubules.
Tertiary dentin is either reparative or reactive, and responds to a noxious stimulus. The teritiary dentin is iregular and may not be acelular (like it should be) or may not have tubules like ti ought to
Bt what layers is the predentin found?
The predentin is hte layer is found bt the minerlaized dentin and the dentinopulpal border (superficial/beyond the tight juncitons of the obd cell bodies)
predentin= unmineralized dentin material. It is secreted by the odb process.. ODB cell bodies are in hte pulp and their processes extend through the dentin layer.
Is the mantle or circumpulpal dentin more mineralized?
The circumpulpal dentin in more mineralized than the mantle dentin
where is the mantle dentin located in the tooth?
The mantle dentin is located just inside the DEJ/ it lines the DEJ.
the mantle dentin is less mineralized than the circumpulpal dentin which is centralized to the dentin (deeper) and more mineralized than the mantle
When and Where is secondary dentin found?
Secondary dentin is the dentin that forms after root development is complete. Secondary dentin located centrally to primary dentin (deep to primary dentin) - secondary dentin may be called circumpulpal dentin
Does primary dentin form faster or slower than secondary dentin?
Primary dentin forms faster than does secondary dentin
what impact does the secondary dentin have on the pukpal chamber?
Secondary dentin forms throughout life (from after root development thru life..) as such, the pulp chamber is reduced in size with older age
How is hte strucure of secondary dentin compared to that of primary dentin?
The strucuture of secondary dentin is the same as that of primary dentin
What is the difference between reparative and reactive dentins?
Both reparative and reactive dentins are teriary dentin that forms only in a specific location (site of injury) in response to a noxious stimulant. – the difference:
- reactive dentin is made by the original odb (from odontogenesis start) while
- rperative dentin is formed by replacement odb
T/F all dentin is acellular
False. While dentin is supposed to be acellular (minerlaized!), the teritary dentin may have cells. Tertiary dentin is IRREGULAR. it may have cells, it may not have tubules.
Tertiary dentin (reparative and reactive types) is formed in a specific place DUE to a noxious stimulant.. the
Of all the dentin in the tooth, is there more primary or more secondary dentin present?
There is more primary dentin than secondary dentin in the tooth.
– Even though primary dentin only forms up to the point of final root development, there is still more primary dentin formed in the tooth than there is secondary dentin (which forms SLOWLY from the end of root development through life)
Histologically, put in order what stains darker from most to least: tertiary, secondary, primary dentins
Histologically, tertiary dentin stains the darkest, then secondary and primary dentin stains the lightest.
tertiary dentin apperas in places of injury, secondary dentin is circumpulpal and more central to the priamry dentin, and the priamry dentin stains the lightest, composes most of the dentin, and has both circumpulpal and mantle parts.
where is intertubular vs intratubular dentin found?
intertubular dentin is BETWEEN the dentin tubules, while INTRAdentin is the INSIDE LINING of the tubules.
there are other differences..
- -intratubular is more mineralized than intertubular
- -intratubular has a thicker ring of lining in dentin near the DEJ (mantle) than at the dentinopulpal junction. ((hence the reason that mantle dentin has smaller diamter tubules than thsoe at dentinopulpal junction.. bc the intratuublar dentin is thicker at the DEJ, so tubule opening is thinner) AND AKA, outer dentin tubules (aka at the DEJ) have smaller diameter tubules than inner dentin.
which type of dentin is more mineralized:
intertubular v. intratubular
mantle v. circumpulpal
intratubular dentin is more> mineralized than interttublar dentin
circumpulpal dentin is More> mineralized than mantle dentin
is there a greater volume of intertubular or intratubular dentin in a tooth?
there is a greater volume of INTERtubular dentin than intratubular.
:think: intertubular is all the space bt the tubules (which are less dense in the outer tubules (inner dentin has more tubules than does outer) ) while the intratubular is a LINING
– also recall histo slides pics:: lots of space bt the tubules. so lots more intertubular dentin present
How does translucent or sclerotic (2 diff types of dentin) appear when it completely fills a tubule? ((either as inter or intra tubular dentin)
Both translucent and sclerotic dentin appear to be TRANSLUCENT/ clear when the inter/intratubules are filled with it.
- translucent dentin is normal with aging
- sclerotic dentin is accelrated mineral deposition due to caries or attrition.
- —- the filling of the tubules w weither type of dentin is kind of good bc it walls off the tubules and it protects the pulp.. so prevents microbes
would the fillong of tubules by translucent or sclerotic dentin be considered good or bad?
having tubules fill woth either sclerotic or translucent dentin is actually a good thing. This hypermineralization walls off the pulp by filling up the tubules w mineral salts. the clogging of tubules also prevents microbes from inhabintg.. so this filling up has a protective effect = good
what is a dead tract and what does it look like?
A dead tract is what a tubule is called when it dries out and fills with air. the tubule will look opaque.. but stained the same color as surrounding dentin, just much more opqaue.
– recall that dentin tubules Should contain a lot of fluid.. do if they dry out = no longer vital. dead tracts assoc with caries (and aggresive dentistry)
where can interglobular dentin be found?
interglobular dentin appears like mottles/scattered sand just center to the mantle (which stains lightly under the DEJ border) .. the interglobular dentin is HYPOmineralized
is interglobular dentin hypo- or hyper- mineralized?
interglobular dentin is hypOmineralized and is found just deep to the mantle dentin layer
During initial mineralization of the dentin, discrete centers of minerlziations occur called CALCOSPHERITES and these are supposed to fuse.. what happens if they do not?
The calcosperites are little spheres of initializing mineralization.. the space bt these calcospherites should blend as they fuse to form the mature, mineralized dentin.. if they do not fuse, they will remain discrete bundles of unfused dentin == INTERGLOBULAR DENTIN. interglobular dentin is HYPOMINERALZIED
considering the role of DSPP (and your knowledge of the research) is there more or less interglobular dentin present in a DSPP knockout mouse?
DSPP = codes for the minerlaization protein, phosphoryn (think- cirucmpulpal dentin and heterogenous nucleation) .. so, if DSPP knocked out, we would expect malforming dentin with deficinet mineraliztion ability… == expectation and Evidence shows that DSPP knockout = MORE interglobular (aka deficinet/ malformed) dentin
what is tome’s granular layer
Tomes’ granular layer is not exaclty known.. but it is always present bt the cementum and dentin of the tooth in the root – appears as a dark, speckled layer bt the cemntum/dentin layers
T/F growth lines are laid down by the dentin
TRue. Like enamel, dentin has growth lines as the layers are subsequently laid down. the lines are essentially parallels and they are like blankets covering the tooth (in terms of the lay of the layers)
(recall, enamel growth lines called Lines of Retzius)
why may Tetracycline be seen in the growth layers of dentin?
Tetracycline is an antibiotic that binds to developing mineralzied oral tissues.. as such, if tetracycline in system during tooth devleopment, it is incorporated as dark staining into the layers of mineralized tooth tissue
