Dentin and Pulp Complex I Flashcards
Which part of the tooth is Protective?
Enamel
What part of the tooth is the structural component?
Dentin
What is the main cellular component of the tooth?
Pulp
What is the composition of dentin?
70% Inorganic
20% Organic
10% Water
*Highly analogous to bone
The crown is covered by _________
Enamel
The root is covered by ______
Cementum
What is the “water” that helps compose the dentin?
Physiological fluid
What is the inorganic material of dentin?
Hydroxyapatite
What can fluoride replace in the hydroxyapatite crystal?
OH
What other ions can replace components of hydroxyapatite?
Magnesium and Zinc
In Dentin, what are the dimensions of the HA crystals?
60-70 nm Long
20-30 nm wide
3-4 nm thick
What are the respective Knoop Numbers of Dentin, Enamel, and cortical bone?
Dentin: 68
Enamel: 343
Bone: 50
**This is a measure of the hardness of the substance
Organic components make up 20% of dentin. What is the make up of the organic component itself?
90% collagen (mostly I, some III and V)
10% Non-collagenous proteins
What is the purpose of the collagen in the organic material?
Fibrillar collagen scaffold upon which HA crystals are laid down
What Non-collagenous proteins do bone and dentin have in common?
- Bone Sialoprotein (BSP)
- Osteopontin (OP)
- Osteocalcin (OC)
- Osteonecdtin (ON)
- Matrix Extracellular Phosphoglycoprotein
What additional proteins does dentin have that are not found in bone in high abundance?
- Dentin Matrix Protein-1 (DMP-1)
- Dentin Sialophosphoprotein (DSPP)
- Further cleaved into other proteins**
What proteins is DSPP cleaved into?
- Dentin Sialoprotein (DSP)
- Dentin Phosphoprotein (DPP)
- Dentin Glycoprotein (DG)
What cleaves DSPP into it’s three derivative proteins?
BMP-1
DSP is a ________ that is expressed in _________ and may act to prevent _________ and is similar to ______
- Proteoglycan
- Dentinal Tubules
- Mineralization
- DMP-1
DGP is a __________ that may have a role in ________ , but really it’s function is ________
- Glycoprotein
- Biomineralization
- Unknown
DPP binds lots of _______ and initiates ________. It is attached to _____ and is not thought to be _______
- Ca2+
- HA formation
- Collagen
- glycosylated
What do Defects in DSPP cause?
Dentinogenesis Imperfecta types II and III
What is type I dentinogenesis Imperfecta and what causes it?
- Pulp chambers filled with abnormal dentin
- Results from OI (defect in collagen I)
**OI: osteogenesis imperfecta
DSP comes from which end of DSPP?
N terminus
DPP Comes from which end of DSPP?
C terminus
What is Type II Dentinogenesis imperfecta?
- Pulp chambers filled with abnormal dentin
- Caused by DSPP defect
What is Type III dentinogenesis imperfecta?
- Enlarged pulp chambers
- Hypo-mineralization
- Possibly failure of DSPP expression
Dentin is synthesized by _______ which line the __________
- Odontoblasts
2. Pulp Chamber
What is the origin of dentin cells?
Mesenchyme
Odontoblasts are ________ cells which extend cellular ______ into the dentin through ______
- Polarized
- Projections
- Tubules
What gives rise to the dentin-pulp complex from an embryological perspective?
Dental Papilla
What is described as a critical interaction with the inner enamel epithelium?
Initial differentiation
Odontoblasts differentiate and fill the _________ between the _____ and the _______
- Acellular zone
- IEE
- Dental papilla
The interface between the enamel and dentin is called the _______
DEJ
Describe the edge of the DEJ
Scalloped
Why is the shape of the DEJ so critical?
- Defines the shape of the crown
2. Keeps dentin directly attached to enamel during loading (no shearing)
Describe the binding of the DEJ
Bound together by a merging of enamel HA and dentin HA crystals in ridges, which are most pronounced
T/F Odondoblasts conintue to synthesize dentin through the life of the tooth
TRUE
T/F Dental/enamel Shearing is bad
TRUE
What is the first layer of dentin called that is formed closest to the DEJ?
Mantle Dentin
What are Von Korff’s fibers?
.1-.2mm collagen III fibrils associated with fibronectins
What is formed when dentin penetrates the IEE?
Enamel Spindles
Developing odontoblasts begin extending processes into the developing matrix. What are those processes called?
Tomes’ Fibers
What do the ondontoblastic process in the developing matrix secrete?
Dentin Matrix components
How do Von Korff’s fibers contribute to the formation of the DEJ with the ‘scalloped’ edge?
The extend towards the IEE and branch into the ground substance of the developing matrix
Odontoblasts produce matrix as it moves away from the _______
DEJ
As Odontoblasts move away from the DEJ, they leave behind ________
Tomes’ Fiber
What does tomes’ fiber eventually become?
Odontoblast Process
Dentin starts as what?
Predentin which is a non-mineralized organic matrix
Mineralization of dentin starts within ________, which are deposited along the ______
- OD secreted vesicles
2. Future DEJ
Secreted matrix vesicles rupture and release ________
Mineralized matrix crystals
T/F Mantle Dentin is Tubular
FALSE
What is Mantle Dentin formed by_______
the mineralized matrix crystals released from matrix vesicles
After the formation of mantle dentin, what regulates subsequent dentin formation and what does it result in?
- Non-collagenous matrix proteins
2. Tubular primary dentin
When does the formation of Circumpulpal dentin begin?
After DEJ formation
To form root dentin, what initiates odontoblast differentiation?
Hertwig’s Epithelial Rooth Sheath
What does HERS eventually break down into?
Epithelial rests of Malassez
T/F the formation of Root dentin is very similar to the formation of Coronal Dentin
TRUE
What are some possible differences between root dentin and coronal dentin formation?
- Mainly anatomical
2. Some mingling of dentin collagen with cementum collagen
What are the 3 types of dentin?
Primary
Secondary
Tertiary
Describe Primary Dentin?
- The first dentin formed during development
- Compromised the mantle dentin and initial deposition of circumpulpal dentin
Describe secondary dentin?
- Tubular dentin laid down subsequent to root formation
- Produced throughout life
- Continous with primary dentin, but histologically distinct
What is one morphologic difference between coronal dentin and root dentin?
Coronal dentin tubules have a sigmoidal curve, root dentin tubules are much straighter
What is caused by greater secondary dentin deposition around roof and floor?
Pulpal recession
Describe pre-dentin
Not yet mineralized dentin, histologically distinct from other types
Why would tertiary dentin be produced?
In response to insult
Can tertiary dentin have tubules?
Yes, but it often does not.
If Tubules are present, they are often disordered and can ‘include’ cells
Tertiary dentin acts to seal off _________ or to form bridges between dentin and __________ , or in response to ______
- Dentinal tubules
- Restorations
- Trauma
What is reactionary Dentin?
- Tertiary dentin
- Forms in response to trauma that does not damage odontoblasts
What is Reparative Dentin?
- Tertiary Dentin
- Forms in response to trauma that damages Odontoblasts
Formation of reparative dentin involves the recruitment and differentiation of what?
Mesenchymal cells, which form new odontoblasts
In the formation of reparative dentin you have less DSP and DMP-1, and more BSP and OP T/F
TRUE
What is the primary structure of the Dentin Macrostructure?
Tubules
Within the context of Dentin Macrostructure, what are the 3 main structures in dentin?
- Dentin Tubules (With OD process)
- Peritubular Dentin
- Intertubular Dentin
Dentinal tubules run from ______ to _______
- The DEJ
2. OD layer of the pulp
T/F Dentinal Tubules are fluid filled
TRUE
Describe the density of dentinal tubules
- Very high
- 59k-76k/mm squared in apposition to the pulp
- Around half of that density at the DEJ
Dentinal tubules are surrounded by highly calcified collars of ______
Peritubular dentin
Dentinal Tubules are separated by _______
Intertubular Dentin
Describe Intertubular dentin
50-200nm collagen I fibrils arranged perpendicular to tubulese
Dentinal tubules can form secondary branches, where are they most likely to do this?
In the root
T/F Dentinal tubules provide mechanical support to the enamel during loading
TRUE
T/F Dentinal Tubules have implications for the formation of carious lesions
TRUE
After breaking through the DEJ, bacteria move _______ through ________
- Rapidly
2. Tubules
What do bacteria do to the mineralized matrix and protein scaffold?
- Mineralized matrix is liquefied
2. Protein scaffold eroded
What is the response of dentin to the infiltration of bacteria?
Formation of tertiary dentin to occlude tubules
What are “dead tracts” in ground sections?
- Trapped air in empty tubules
- Sealed off after odontoblast death (insult of apoptosis)
What is Sclerotic dentin?
It is a collective term for tubules that have become occluded
Describe the appearance of Sclerotic dentin
Glassy, translucent appearance ( in a ground section)
How does sclerotic dentin happen?
- Occurs naturally, with age as peritubular dentin is deposited
- Can occur by:
- Mineralization only
- Diffuse mineralization around a living OD process
- Mineralization of the cellular process and the collagen fibers along the inside of the tubule
In what direction would sclerotic dentin form?
Starts apically, continues toward the crown with age
What is Interglobular dentin?
Areas of Hypomineralized dentin
When would interglobular dentin form?
When fusion of mineral containing vesicles fail
A vitamin D deficiency or fluoride exposure during initial dentin formation can be associated with what?
Interglobular dentin formation
Where would you more commonly find interglobular dentin?
Near Mantle dentin
Tubules often run through areas of _________, matrix is present
Interglobular dentin
Dentin matrix is deposited contiually at rate of _______
4um/day
Every _ days, there is a layer deposited which has a noticeably different orientation of _________
Collagen fibers
The deposition of different orientation of collagen fibers every 5 days forms what?
Lines of Von Ebner
*Which can be seen at around 20um intervals
Every 12 hours around ____ of mineralization occurs
2um
Secondary dentin is deposited ________, more slowly
asymmetrically
What are Contour lines of Owen?
Enhanced lines that indicate disruption of tooth formation (Like neonatal line)
**They are equivalent to striae of retzius in enamel, which also has a neonatal line
T/F Tetracycline banding is influenced by/follows the pattern of the cyclical deposition of primary dentin
TRUE
What does the granular layer of Tomes look like?
Funny looking dots around the roots of ground sections
T/F The Granular Layer of Tomes gets more granular toward the apical end of the tooth
TRUE
What are 3 possible explanations of what the Granular Layer of Tomes is?
- Hypomineralized areas of dentin, similar to interglobular dentin
- Part of looped dentinal tubules found in the root sections, an artifact of sectioning
- Specialized dentin structures which form part of the dentin-cementum junction
