Describe why the pulp and dentin are known as the pulpodentin complex.
Permeability of dentin regulates the rate of inward diffusion of irritants that initiate pulpal inflammation and the outward diffusion of dentinal fluids that contain immunoglodulins
Dentin and pulp are ________ coupled
Explain what it means for the dentin and pulp to be functionally continuous?
When the external seal is broken (Eg enamel and dentin) are lost for any reason, the normal compartmentalization of the two tissues is lost
What is the short term response in a functional continuum for dentin and pulp?
Acute inflammatory response, producing outward movement of fluid and macromolecules
What is the long term response in a functional continuum for dentin and pulp?
Tertiary dentin formation to reduce permeability
What is the importance of pulpal blood flow?
To clear pulpal interstitial fluids of exogenous (noxious) material.
Odontoblast cell bodies reside in
the pulp chamber
If you perform an endodontic procedure, what do you leave behind at the pulpal dentin interface?
- No peritubular matrix
- 2-3 μm in diameter openings
- predentin removed
- calcospherites (the openings are here
Dentin is a ______ biologic _______ made up of ________ crystal filler particles in a ________matrix.
Acid etching or EDTA ______ removes the ________ dentin matrix, thereby ________ the tubule orifice, and _________ the mineral crystallites from around the _______ _______, exposing the ________ nature of the _________ dentin matrix
- collagen fibrils
What percent is mantle dentin in mineralization?
How wide is mantle dentin?
When is secondary dentin formed?
After root formation
In coronal pulp and especially over pulp horns what morphology do odontoblasts develop?
Pseudostratified columnar layering as they move closer together
Odontoblasts are _______ in the root canal and become _____ near the apex.
Convergence of odontoblasts leads to what density of tubules?
- 5:1 in coronal dentin
- 2:1 root dentin
What is another name for peritubular dentin?
Intratubular or periluminal dentin
Describe peritubular dentin at the DEJ.
- Old dentin
- Large amount of at DEJ
- Accounts for small diameter of tubule
What are giant tubules measuring?
- fewer than 30 per tooth
Tubules account for __% of surface area at DEJ and __% at the pulp
The mineral in peritubular dentin is in the form of _____, ______-deficient, ______-rich apatite crystals, which have _____ crystallinity and are almost _____ times harder than intertubular dentin.
What accelerates peritubular apposition?
- Occlusal abrasion
- More rapid in primary tetth
What ions may dentinal fluid contain?
Calcium and phosphate
Dentin can remove ____% of a bacterial suspension of _________ that approximately ___ in diameter when pressure is applied to the solution
Bacteria cannot invade very far into a dentinal tubule because
dentinal fluid moving outward contains immunoglobulins (G1)
Do fluid shifts across the dentinal tubule allow bacteria to invade the pulp?
No, because the tubules or the interlumin had collagen fibrils and mineral deposits that stop bacteria
What is the range of water percent in dentinal tubules?
- 1% at DEJ to 22% near the pulp,
- deeper resin restoratives have to fight water for empty collagen fibrils
What are water blisters?
- Transudation of water from dentinal tubules during bonding to vital dentin
- Raise stress and affect integrity of bonded surfaces
Do water blisters form in endo tx teeth?
No, therefore bonding to endo treated teeth is excellent!
Describe dentin composition?
- 70% mineral
- 20% organic
- 10% water
Because of the low/high density of dentin, the weight percentage is much higher/lower than volume percentage
Describe the apatite crystal in dentin.
Smaller than in enamel, therefore, more susceptible to hydrogen ion attack (pH 6.7)
Mineral content in dentin, include inter tubular and peritubular.
- 95% in peritubular
- 30% in intertubular
Dentin Knoop hardness?
68 vs. 343kg/mm2 enamel
Dentin elastic modolus?
11-20 vs 86GPa
Modulus of elasticity is lower, is dentin therefore stronger?
Yes, that is why it is stress-breaking and shock absorbing for enamel
NaOCl reduces mechanical properties of dentin, how?
- Sims et al 15% réduction in dentin stiffness
- 39% reduction in flexural strength
- 5.25% for 2 hours
What can long term CaOH use do to dentin?
More than 30 days, reduce fx resistance of root dentin
Why do old teeth develop fatigue cracks faster?
Occluded tubules have more mineral crystals that results in less hydration
What do Moire gratings allow us to do?
They are 200 lines/mm gratings applied to sections of teeth to measure 2D strain fields
Where are the low modulus areas on dentin?
At the CEJ and just below the DEJ (stress cushions and buffers)
Strains in the tooth are distributed how?
Max is at cervical, intermediate at middle third, and no strain over apical root. Why? Hypothesized to protect the venous outfllow during occlusal forces
CD (Coronal Dentin) Tubular density varies from _______ at the DEJ to ______ at the pulp.
CD Permeability of dentin is highest for _____ molecules such as ______, lower for larger molecules such as _______ and ____________, and still lower for molecules with molecular weight greater than 10?, such as _________
- albumin, immunoglobulins
CD Dentin permeability categories are?
Transdentinal movement and Intradentinal movement
CD What is transdentinal movement?
Movement of substances through dentinal tubules, such as fluid shifts in response to hydrodynamic stimuli
CD What is intradentinal movement?
Exogenous substances into intertubular dentin as occurs with infiltration of hydrophilic adhesive resins or demineralization of intertubular dentin by acids
CD Axial dentin is much _____ permeable than occlusal dentin.
CD Where is permeability of dentin highest during restorative work?
Gingival floor, proximal boxes, gingival extensions of finish lines in crown prep
CD How many exposed tubules in crown prep per 1cm2?
RD What is main factor in reducing apical root dentin permeability?
Age, third decade of life commencement of tubular sclerosis
Soaking dentin disks in 5% NaOCl for 1 hour produces
105% increase in hydraulic conductance
How long are smear plugs in instrumented dentin?
Instrumentation with K files decreases the permeability of ROOT DENTIN by ___%.
Current endodontic sealers are too ________ to penetrate the exposed collagen fibrils by ________ permeation
Root dentin has a permeability that is only __-__% great as that of coronal dentin.
How much root dentin has to be removed after cementum is to affect permeability?
Cervical and middle root dentin have _____ permeability than apical dentin, consistent with their _____ tubular density as compared to apical dentin.
Permeability of pulp floor chamber at furcation?
High, due to accessory canals especially after NaOCl tx
Describe antidromic stimulation of the inferior alveolar nerve?
- Cats had electrical stimulation of the IAN causing deploarizaton of nerve terminals
- Release of neuropeptides from terminals causes increased pulpal blood flow and extravasation of plasma proteins
What did Matthews and Vongsavan postulate about the flow of dentinal fluid?
That is outward in vivo, they tried to diffues Evans blue dye in vivo bu could not and in vitro they did. It is "Solvent drag", hydrodynamic stimulation of exposed dentin evoking a release of neuropeptides from nerve terminals which increase pulpal blood flow forcing outward on the tubules and expelling anything noxious.
Do we have an outward flux of fluid with a smear layer (non-hypersensitive dentin)?
No, it is inward since there is no hydrodynamic stimulation. -noxious substances may inc, + ↑ topically applied agents in the pulp
There are two defenses against noxious stimuli, one being the outward flow of fluid, but what is being found as a second defense?
Outward flux of plasma proteins like fibrinogen
The _______ molecule may be responsible for reducing dentin permeability, especially at the pulpal terminations of the tubules, where it may ________ into _____.
What activates the mechanoreceptors in dentin?
Which neuropeptide is implicated in rats to cause neurogenic inflammation?
Calcitonin gene related peptide or substance P
The permeability of dentin varies where on the ________ surface only __% of the tubules are in communication with the pulp.
About __% of the organic portion of the dentin matrix is made up of (list 4)
- Type 1 collagen
- non-collagenous protein growth factors
The long term effects of having bacteria trapped in tubules depends on these two:
- effects of immunoglobulins
The study with MTAD Biopure mentioned
The study with EDTA and soaking teeth in water for months, who?
The study with K files ↓ permeability by 49%
The study with root resection, the ↑ angle of resection the ↑ chance of microleakage, who?