2.6 Dental pulp pt 1

Mineralised Protective Component

enamel

Mineralised Structural Component

Dentin

Main Cellular Component

Pulp

Which portion of the tooth is avital

enamel

Is dentin avital

no it does technically have cellular projections

Dentin composition is highly analogous to

bone

Dentin of the crown is covered by

enamel

Dentin of the roots is covered by

cementum

Dental is composed of how much inorganic material

about 70%

Is the inorganic component of both dentin and enamel that same

yeah its mostly HA

Dentin is composed of how much organic material

20%

Is the organic compnent of dentin and enamel the same

no different proteins. enamel has no collagen

Dentin is composed of how much water

about 10%

Where is the water content mostly found in dentin

within tubules

Each crystal unit cell of HA has

Ca₅(PO₄)₃(OH)x2

Effectively HA is a

calcium phosphate crystal

During cases like water fluoridation, what happens to HA

Fluoride can replace the OH

What gives us the mechanical structure of dentin

tubule structure

In dentin HA crystal are arranged how

arranged in rectangular plates, 60-70 nm long, 20-30 nm wide, 3-4 nm thick

Arrange the following from least to most hard- Dentin, enamel, and cortical bone

Cortical bone —> Dentin —> Enamel

Vast majority of organic material in dentin is

90% collagen fibers, primarily type I (some type III, V)

10% of organic component is

non collagenous proteins

Non collagenous proteins in common with bone

contain “osteo” so Osteopontin (OP) Osteocalcin (OC) Osteonectin (ON), etc

Non collagenous proteins specific to dentin

Dentin matrix protein-1
Dentin sialophosphoprotein (DSPP)

Dentin sialophosphoprotein (DSPP) can be cleaved into

A) Dentin Sialoprotein (DSP)
B) Dentin Phosphoprotein (DPP)
C) Dentin Glycoprotein (DG)

Most dentin specific proteins

Also found in bone, just in a MUCH lower proportion 1/400th

N-terminus of DSPP

is what gets cleaved into Dentin Sialoprotein (DSP)

Middle of DSPP

makes Dentin Glycoprotein (DG)

C teminus of DSPP

gets cleaved to Dentin Phosphoprotein (DPP)

DSPP gets cleaved by

Rapid Cleavage by BMP-1

Dentin Sialoprotein (DSP)

Proteoglycan expressed in dentinal tubules to prevent mineralization

Dentin Sialoprotein (DSP) is similar to

DMP-1

Dentin Glycoprotein (DG)

glycoprotein likely with role in biomineralization but largely unknown

Dentin Phosphoprotein (DPP)

attached to collagen and binds tons of Ca2+ to initiate HA formation

Defects in DSPP

can cause dentinogenesis imperfecta types II and III

Type I dentinogenesis imperfecta

Results from OI (defect in Collagen I), pulp chambers filled with abnormal dentin making them very brittle

So type I dentinogenesis imperfecta is associated with which condition

Osteogenesis imperfecta

Osteogenesis imperfecta

is a genetic disorder characterized by fragile bones due to defects in type I collagen, leading to increased bone fragility and a tendency to fracture.

type II dentinogenesis imperfecta

NOT associated with OI (DSPP is produced but defective), pulp chambers filled with abnormal dentin

type III dentinogenesis imperfecta

Enlarged pulp chambers, hypo-mineralization, possibly failure of DSPP expression

Which forms of dentinogenesis imperfecta are associated with DSPP defect

type II and type III

dentinogenesis imperfecta type II where pulp cavities are filled with abnormal dentin

Dentin synthesized by

odontoblasts

Odontoblasts line the

pulp chamber

Pulp chamber comes from

dental papilla

Odontoblasts are polarized cells which

extend cellular projections into the dentin through tubules

Origin of odontoblasts

mesenchymal (NEURAL CREST!)

Dentin-Pulp Complex arises from

dental papilla

initial differentiation of odontoblasts is stimulated by

critical interaction with the inner enamel epithelium

Odontoblasts differentiate and fill the

the acellular zone between the IEE and dental papilla

Vascular support arises from

dental papilla

What is inside the tubules

tomes fibers which project to the DEJ

Layer on top of ameloblasts that helps facilitate growth

stratum intermediate

Odontoblasts secrete

pre-dentin (undermineralized) like osteoid

What signal tells the odontoblasts to start secreting pre-dentin

CHECK

What can ALWAYS be found near the odontoblast (throughout life)

a layer of predentin because they continuously secrete forever (just slow down)

What do odontoblasts leave behind

tomes process

DEJ

interface between the enamel and dentin, where they are in direct apposition

Morphology of the DEJ

scalloped edge due to increase surface area for interlocking

WHy do we need increased surface area for interlocking on the DEJ

it has to resist a lot of shearing force

The shape of the DEJ is critical for which 2 reasons

1) Defines the shape of the crown
2) Keeps dentin directly attached to enamel during loading (no shearing)

Why do we have dentinal tubules

to help distribute the force for cyclical loading

In the ridges of the DEJ there is a slight

merging of enamel HA and dentin HA crystals

First layer of dentin formed

Mantle Dentin (closest to DEJ)

Mantle dentin

the outermost dentin found at the DEJ (20 microns thick so very thin )

Von Korff’s fibers

collagen III fibrils, associated with fibronectin which extend toward IEE and form DEJ scalloped edge

Developing odontoblasts begin extending processes called

Tomes’ fibers

Tomes fibers

which are cytoplasmic extensions of odontoblasts that extend into developing tubule system (matrix) and secrete dentin matrix

Penetration of the IEE by OD

makes enamel spindles

So overall the odontoblasts make a

dentin protein scaffold, ready for mineralization

Odontoblasts produce

matrix, moving away from the DEJ

Odontoblasts leave behind

‘Tomes’ Fiber’ (future odontoblast process)

Wherever this is a tomes fiber there will be

a dentinal tubule

Dentin starts as

non-mineralized organic matrix (predentin)

Mineralization starts within

OD secreted matrix vesicles, deposited along the future DEJ

Globular mineralization

is the process where mineralization occurs in a localized manner, leading to the formation of spherical mineralized areas in the dentin THROWING WATER BALLOON AT WALL

Linear mineralization

occurs in a continuous manner, forming a layered structure of mineralized dentin PAINT ROLLER

Secreted matrix vesicles rupture to release

mineralized matrix crystals

Initially mantle dentin is

non-tubular until the matrix proteins regulate it

Non-collagenous matrix proteins regulate

subsequent dentin formation, resulting in tubular primary dentin

After DEJ formation with mantle dentin,

‘circumpulpal’ dentin formation begins

‘circumpulpal’ dentin

the dentin surrounding the pulp chamber

What initiates odontoblast differntiation in the root

Hertwig’s root sheath (HERS)

HERS eventually breaks into

Cell Rests of Malassez

Root dentin formation is

Very similar to coronal dentin formation

Primary Dentin

The first dentin formed during development, Comprises the mantle dentin AND the initial deposition of circumpulpal dentin

Secondary Dentin

Tubular dentin laid down subsequent to root formation.

When is secondary dentin produced

throughout life after tooth development

When is secondary dentin is continuous with

Continuous with primary dentin BUT histologically distinct

Coronal dentin tubules have a

sigmoidal curve

root dentin tubules vs coronal

root dentin tubules much straighter

Greater secondary dentin deposition around

roof and floor causing pulpal recession

Tertiary Dentin

Dentin produced in response to insult

Often times tertiary dentin

does not have tubules