2.7 pulp 2

Tertiary dentin

Dentin produced in response to insult, can be reactionary or reparative

Function of tertiary dentin

Seals off dentinal tubules or forms bridge between dentin and restoration

Tertiary dentin- reactionary

Trauma doesn’t damage odontoblasts.

Reparative tertiary dentin

Odontoblasts are damaged so so we need to recruit mesenchymal cells from pulp to make new ones

Signaling in tertiary odontoblasts differentiation in reparative tertiary dentin

More BSP and OP than DSP and DMP-1

Dentin bridge

Hopefully happens during restoration where odontoblasts plug up to the margin with dentin to strength it and increase longevity

Histological appearance of tertiary dentin

Often has no tubules, but if they are there they are disordered

3 main structures in dentin

Dentin tubules

Peritubular dentin

Intertubular dentins

What can happen to tomes fibers in response to inflammation or mechanical damage

They quickly make dentin, causing the tubules to decrease in diameter and seal off more

Peritubular dentin

Collar of highly mineralized dentin around tubules

Secondary dentinogenesis is active where

Peritubular fibers

Dentinal tubules run from

DEJ to the odonotoblast layer of the pulp

What’s inside dentinal tubules

Fluid and tomes fibers

Highest tubule density

Very high in direct opposition to pulp, half that at DEJ

What separates dentinal tubules

INtertubular dentin

INtertubular dentin

50-200nm collagen I fibrils arranged perpendicular to tubules

Secondary branches of dentinal tubules

More common in the root which help provide some flexibility and mechanical support to the enamel and pulp during loading

Dead tracts/ Sclerotic dentin

Collective terms for tubules that have been occluded

Dead tracts

Have an end sealed off but are otherwise ‘empty’. Appear black in ground sections

Sclerotic dentin

occurs when tubules are totally filled; has a glassy, translucent appearance in ground section

In which patients would you see more dead tracts and sclerotic dentin

More elderly sine it happens with age

Dead tract and sclerotic dentin form from what

As Peritubular dentin is deposited starting apically and continuing toward crown

Interglobular dentin

Batwing formations from hypomineralized regions of dentin

Increased interglobular dentin is associated with

Vit D deficiency or over fluoridation during initial dentin formation

Interglobular dentin is more common where

In mantle dentin

Tubules in Interglobular dentin

Tubules run though with matrix present

Enamel spindles

result from result from odontoblastic processes that traverse the DEJ and penetrate the enamel

Enamel spindles appear

•Often appear at incisal and cuspal tips.

Enamel spindles are NOT

Made of enamel, they have some dentin (collagen)

Cyclical deposition of primary dentin

4 micrometers/day

How many days do odontoblasts secrete and then pause

Every 5ish days, they pause and then you can see a slightly different orientation of collagen fibers

Lines of von Ebner

Slights different orientation of collagen fibers from the 5 day cycle of odontoblasts

Lines of von ebner are see at what intervals

Every 20 micrometers

Mineralization cycles

Around 2 micrometers every 12 hrs

Contour lines of Owen

enhanced lines that indicate disruption/alteration in tooth formation (i.e. neonatal line). Equivalent to Striae of Retzius in the enamel (where there is also a neonatal line).

Tetracycline banding

Can occur in both enamel and dentin as it bind unmineralized

Granular layer of tomes is where

Found at junction between cementum and dentin —> ROOT DENTIN

Hyaline layer of hopewell-smith

Last part of root dentin that mineralizes nest to CD junction

Hyaline layer of hopewell smith contains

Mingles enamel matrix proteins with dentin matrix proteins

So layer of hope well smith is ____ to granular layer of tomes

External

Dental pulp

The living, highly cellular core of the tooth

Primary cell type of dental pulp

fibroblasts followed by odontoblasts

Dental pulp arises from the

Dental papilla

Embryological origin of dental pulp

Ectomesechymal cells (NEURAL CREST)

Outer to inner zones of dental pulp

1) Odontoblast layer

2) Cell free zone of Weil

3) Cell rich (Cell dense zone) 

4) Pulp Core

Dental pulp ECM

Soft connective tissue matrix, comprised of collagen III and collagen I. Numerous non-collagenous proteoglycans and glycoproteins.

Which types of collagen are found in pulp

Collagen III and collagen I

With age what happens to dental pulp ECM

Collagen content increase and fibrils aggregate into big bundles —> greatest concentration is apical

Ground substance of dental pulp

proteoglycans (GAG chains), glycoproteins, water (physiological fluid)

Key dentin-pulp complex cell type

Odontoblasts

Odontoblasts

Polarized cells, elongated nucleus at the pulpal side of cell, secretory components (Golgi Bodies) towards the dentinal side

Odontoblasts in the pulp are healed together by

Junctional complexes (adherens not zolular)

Why is there a slight degree of permeability to the odontoblast layer

Because they are held together by adherens junctions so serum proteins may pass

Odontoblasts can form gap junction with

Pulpal fibroblasts

What layer in the pulp is directly under the OD layer (toward pulp core)

Cell free zone of wile which has small vessels

Function of OD layer in pulp

•Creation and maintenance of dentin, supported by the rest of the pulp

Which type of proteins are produced by ODs

Collagen and non collagenous proteins

Which growth factors are produced and sequestered by ODs

VEGF, TGFβ1, BMP-2)

Why would the OD layer hold on to those growth factors

To stimulate repair

Which part of the OD releases secretory vesicles

From the OD process

Aged odontoblasts

fewer organelles, less secretory activity, nucleus somewhat more central

Why are ODs so hard to study

They’re bound in pulp

What do we think about OD turn over process

assumed to be long lived, can be replaced from mesenchymal progenitor pool

Extent of OD process is not completely agreed upon, what are the 2 options

Quite possibly all the way to the DEJ, perhaps only around 1/3 of the way into the dentin

Predominant cell type in dental pulp complex

Fibroblasts

Where are fibroblasts found in the pulp

The cell rich zone and the pulp core

Functions of fibroblasts in pulp

Produce and maintain supportive matrix (proteoglycans and collagen), KEEPS IT from MINERALIZING!! Keeps if squishy in pulp

Dental pulp progenitor cells

Mesenchymal progenitor cells (adult stem cells) present in dental pulp

Function of dental pulp progenitor cells after dentin damage

They are recruited to form new odontoblast-like cells (REPARATIVE DENTIN)

Immune cells of pulp

Macrophages

Dendritic cells

Lymphocytes

Role of healthy pulp immune system

key role in cell turnover and clearance. Involvement in immune response to infection (IL-1β, TNFα)

Dendritic cells

acquired immunity with antigen presentation to T cells. Found under the odontoblast layer

Dendritic cells are especially closely associated with

neuronal and vascular components of the pulp —> coordinated tissue responses.

T and B lymphocytes are in pulp only under which conditions

Infection

Pulp vasculature arises from the

external carotid arteries and superior/inferior alveolar arteries

Per root, what does the vasculature look like

4-8 arterioles access pulp through apical foramen and spread toward coronal pulp

Progression of pulp vasculature

Arterioles, capillaries, venules

Where is the capillary network in the pulp

In the cell free zone

Difference in vasculature during primary dentin formation

Capillary network is present in OD layer

After traumatic evulsion of tooth, which is it that with kids especially you can put the tooth back in and not always have to have RCT

The vasculature is much more robust and there isn’t a tiny define apical foramen

As arterioles proceed into pulp,

Caliber increases but vessel wall decreases

Little bit of connective tissue you can sometime see on root tip of pulled tooth

Apical papilla covering foramen

Arterioles in the pulp

Anastomose to venules in capillary plexi in cell free zone

Venules leave via

Apical foramen —> sup/inf alveolar veins —> internal jugular

Innervation of dental pulp

nerves which enter through the apical foramen, in close contact with blood vessels (neurovascular bundles)

Plexus of raschkow

Nerve fibers branch out through the coronal pulp —> especially in pulpal horns

There are NO plexus of raschcow in

Root pulp (only branches of nerve fibers)

Incoming nerve fibers consist of

Afferent nerve from the trigeminal AND sympathetic branches from superior cervical ganglion

Why do we have symp innervation in teeth

Blood vessel control

Function of dental pulp innervation

Control blood flow, nociception, immune response?

Nerve bundles consist of both

myelinated ‘Aδ’ and unmyelinated ‘C’ axons

Myelination decreases as

Fibers proceed toward coronal pulp

Some unmyelinated nerve axons pass into

•dentinal tubules and are closely associated with odontoblasts (minority)

The more sustained pulp inflammation we have (very deep lesions through dentin, now LPS is hitting pulp for immune activation)

Reparative dentin process gets UNCOUPLED

Unified pulp homeostasis

Responsive to external stimuli —> Repair response through fibroblasts/odontoblast, supported and replenished by progenitor cell pool

3 proposed models of dentin sensitivity

1) Direct Innervation

 

2) Odontoblast nociception,

3) Tubule fluid conductance (hydrodyna

Direct innervation models

Since those C fibers can go into dentinal tubules, increased can sauce sensitivity

Odontoblasts nociception model

ODs make gap junctions with fibroblasts so they might act as nerves and pass that signal to fibroblast synapse

Tumble fluid conductance (hydrodynamic model)

OD and nerve ending are sensitive to disruption in dentinal fluid (so changes in pressure of fluid stimulates receptors in pulp)

Which model is most accepted

Fluid conductance