Dentin Pulp Complex I Flashcards
What is the function of a tooth?
Survive long-term cyclical loading
What is enamel?
What is dentin?
What is pulp?
Enamel - Mineralized protective component
Dentin - Mineralized structural component
Pulp - Main cellular component
What is dentin composed of?
70% - Inorgo
20% - Orgo
10% - H2O - Physiological fluid water
T/F - There is absolutely collagen (Mostly type I and some type III) in dentin.
TRUE
*Build on a collagen matrix
What is the inorgo material?
HYDROXYAPATITE
Like enamel crystals, but organized in a collagenous matrix
Ca10(PO4)6(OH)2 or Ca5(PO4)3(OH)2
Effectively, what is the HA in dentin?
Calcium phosphate crystals
F- can replace the OH, creating fluorapatite, also Zn and Mg, and others
T/F - Dentin is harder than bone, but weaker than enamel.
TRUE
Of dentin’s 20% organic material, what is the composition of it? Hint: 90:10
90% - Collagen (Mostly I, some III)
10% - Non-collagenous proteins
What are some non-collagenous proteins?
Dentin sialophosphoprotein (DSPP)
Dentin matrix protein-1 (DMP-1)
DSPP is cleaved further into what 3 proteins?
Dentin sialoprotein (DSP)
Dentin phosphoprotein (DPP)
Dentin glycoprotein (DG)
What cleaves DSPP?
BMP-1
Tell me about DSP.
Proteoglycan
Expressed in dentinal tubules
May act to PREVENT mineralization
Similar to DMP-1
Tell me about DGP.
Glycoprotein
Unknown fx
Tell me about DPP.
Only protein
Binds Ca2+, initiates HA formation
Attached to collagen
Defects in DSPP can cause what two malformations of dentin?
Dentinogenesis imperfecta II and III
What is dentinogenesis imperfecta type I?
RESULTS FROM OSTEOGENESIS IMPERFECTA (This is a defect in collagen I)
Pulp chambers filled with abnormal dentin
What is dentinogenesis imperfecta type II?
NOT ASSOCIATED WITH OSTEOGENESIS IMPERFECTA (This is a DSPP defect)
Pulp chambers fill with abnormal dentin
What is dentinogenesis imperfecta type III?
Enlarged pulp chambers, HYPOmineralization
Probably DSPP expression failure
T/F - All types of dentinogenesis imperfecta results in non-vital teeth.
TRUE
Dentin is made by what cells?
ODONTOBLASTS
-Line the pulp chamber
-Mesenchymal origin
—From dental papilla
—Ectomesenchymal origin
T/F - Odontoblasts are polarized cells which extend cellular projections into the dentin thru tubules.
TRUE
T/F - Dentin-pulp complex arises from dental papilla.
TRUE
IEE leads to formation of what?
Odontoblasts
What cells/cellular tissues give the go for ameloblasts to lay down enamel?
Pre-dentin
Look at the figures in the slides, especially for HISTO.
Do it
Why is the DEJ scalloped?
Distribute shear forces
Why is the DEJ shape critical? 2 reasons.
Defines shape of crown
Keeps dentin directly attached to enamel during loading (NO SHEARING)
How is the DEJ bound together?
Merging of enamel HA and dentin HA crystals in ridges
Which type of dentin is closest to the DEJ and the first layer of formed dentin?
Mantle dentin
What are Von Korff’s fibers?
0.1-0.2 mm collagen III fibrils
—Associated with fibronectin
—*These are quite large fibers
Tell me about the matrix formation of dentin.
Extend towards the IEE and branch into ground substance, and then forms DEJ with a scalloped edge
What do developing odontoblasts begin extending into the developing matrix?
Tomes’ fibers
Penetration of the IEE = ??
Enamel spindles
Once a dentin protein scaffold is assembled, what is it ready for?
Mineralization
Odontoblasts produce ________, moving away from the DEJ. When they do this they leave behind ________ ________ (future odontoblast process).
Matrix
Tomes’ fiber
When does dentin mineralization start?
OD secreted Matrix vesicles, deposited along the future DEJ
Once DEJ is formed, which dentin formation then commences?
Circumpulpal dentin
T/F - Secreted matrix vesicles rupture and release mineralized matrix crystals.
TRUE
_____ ______ ______ initiates odontoblast differentiation.
Hertwig’s Root Sheath
What does HERS eventually become?
Rest cells of Malassez
What are the three types of dentin and describe them.
Primary - 1st dentin formed during development, PRIOR TO ROOT FORMATION
—Mantle and initial deposition of circumpulpal dentin
Secondary - Tubular dentin laid down AFTER root formation
—Produced thruout life
—Closest to the pulp tissue
Tertiary - Dentin produced in response to insult
—Can have tubules, but often not
—Acts to seal off dentinal tubules
What is the difference b/t reactionary tertiary dentin and reparative tertiary dentin?
Reactionary - Trauma does NOT damage odontoblasts
Reparative - Damages odontoblasts
—New ODs are formed
—*Less DSP and DMP-1, More BSP and OP
Macrostructurally, what is the primary feature of dentin?
Tubules
What are 3 main structures in dentin?
Dentin tubules - with OD process
Peritubular dentin
Intertubular dentin
What is the orientation of dentinal tubules?
DEJ to the OD layer of the pulp
Fluid filled
*Surrounded by “collars” of peritubular dentin
Provide mechanical support to the enamel during loading
—Give the tooth some “flex” during loading
T/F - After breaking thru the DEJ, bacteria move rapidly thru tubules.
TRUE
What are dead dentinal tracts?
Trapped air in empty tubules - sealed off after OD death (insult or apoptosis)
What is sclerotic dentin?
Occluded tubules
Glassy, translucent appearance
Occurs naturally, with age as peritubular dentin is deposited
*Starts apically, continues towards the crown with age
What is interglobular dentin?
Areas of HYPOmineralized dentin
Formed when fusion of mineral contains vesicles fails
-Can be associated with Vit D deficiency or F exposure during initial dentin formation
More common near MANTLE dentin
Dentin matrix is deposited continually at what rate?
4 microns (micrometers)/day
What forms the lines of von Ebner?
A deposited dentin layer with different collagen fiber orientation
~20 micron intervals
Mineralization occurs around ____ microns every _____ hours.
2
12
What are the contour lines of Owen?
Enhanced lines that indicate disruption of tooth formation
—I.e. neonatal line, Striae of Retzius*
What is the glandular layer of Tomes?
Dots around roots of ground sections
Mysterious
Maybe:
-HYPOmineralized dentin
Origin in Root dentin, so look for cementum, not enamel
Look at slide 30 for a picture
T/F - Tubule density INCREASES as you approach the pulp.
TRUE
In other words, the tubule density at the DEJ is half of that at the pulp
