dentinogenesis and dentin permeability
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Dentinogenesis
and dentin permeability
Dr. Gábor Varga
February, 2016
Department of Oral Biology
Faculty of Dentistry, Semmelweis University
Radiograph of teeth – dentin is the major component
Molar
longitudinal
section
Dentin is the
major
component
of the pulp
Pulp Horn
mantle dentin
tertiary dentin
primary dentin
secundary dentin
predentin
Section of the tooth– types of dentin
I
W
O I
W
O
Wet weight Volume
Constituents of dentin
Water, Inorganic, Organic
Tooth development – details 1
Tooth development – details 2
Section of tooth – pulp is inside
Gene activation during tooth development
Epithelium
Mesenchyme
Differentiation of
odontoblasts
Formation of mantle dentin
during the early phase of
mineralization
Section of the developing tooth
Dentin is produced by odontoblasts
dentin
Predentin
Odontoblasts
Mineralization
front
Mesenchyme
Cross section of a rat insicor illustrating mature secretory odontoblasts
Odontoblast
structure
Mature secretory odontoblast
Involvement of hard tissue proteins in mineral
formation
Interaction of odontoblast secretory products
in predentin, dentin and the mineralization
front
Light microscopic autoradiographs of the
utilization of tritiated proline by odontoblasts at
various time periods after intravenous injection
Collagen fibers are visible after
dissolution of the mineral phase
- dentine tubules are visible
Collagen fibers around
tubules
(A) Primary, (B) secondary and (C) tertiary
or reparative dentin
Dentinogenesis Imperfecta
Dentin phosphoprotein (DPP), a highly acidic
protein, is the major noncollagenous component of
dentin, being solely expressed by the ectomesenchymal
derived odontoblast cells of the tooth. Takagi and
Sasaki (1988) suggested that a deficiency of this protein
is a causative factor factor in dentinogenesis
imperfecta (DGI1; 125490). MacDougall et al. (1997)
demonstrated that 2 major noncollagenous dentin matrix
proteins, dentin sialoprotein (DSP) and dentin
phosphoprotein (also known as phosphophoryn) are
encoded by a single
gene termed dentin sialophosphoprotein (DSPP).
Dentinogenesis Imperfecta
Characteristics
– autosomal dominant
(1:8000)
– Opalescent teeth
– Irregular structure and
hypomineralized dentin,
grey or dark
yellow/brown
Dentinogenesis Imperfecta
Radiology
Onion- or tulip-like tooth
crown
large pulp chamber, narrow
dentin matrix
Dentin permeability, dentin sensitivity
Dentin tubules, inter tubular
and intratubular dentin
Components of dentin
20000/mm2
45000/mm2 0,2-1,0 μm
Number
Diameter
Permeability: the number and the
diameter change depending on the dentin
tubules
Entrance of a dentine tubule
The empty dentin tubules provide the basis
for permeability - longitudinal section
Mineral deposits narrow down dentin
tubules
Debris closing the entrance of dentin tubules
Components of dentin tubules besides
extracellular fluid
Electron micrographs of the odontoblastic process
and nerve ending in dentin
Neuronal network of pulp/dentin
Nerve endings in dentin
Diffusion - Fick’s 2nd law
Js=DsAs / (∆Cs∆x)
• Js: diffusion rate
• Ds: diffusion coefficient
• As: size of cross sectional surface
• ∆Cs: concentration gradient
• ∆x: length
Hagen – Poiseuielle equation
- fluid movement -
basis of the hydrodynamic theory
V=π∆Pr4 / 8ηL
• V: fluid movement
• ∆P: pressure difference
• r: radius
• η: viscosity
• L: length
Dentine sensitivity
• Dentinal tubules pass from pulp to dentine
surface
• Contain dentinal fluid
• Pulpal one third of dentine contains
odontoblast processes and some nerve fibres
• Problem: how can dentine transmit stimuli?
Dentine sensitivity
• Hydrodynamic theory of dentine sensitivity
- fluid movement and pressure changes
• Is sensitivity due to nerve fibers in tubules?
• or movement of odontoblasts?
• Could odontoblasts be sensory endorgans?
• Are nerve fibers in the subodontoblastic plexus
the actual sensors?
Dentine sensitivity
• Great variation between subjects
• secondary dentine and sclerosis of dentine
In a caries lesion, cariogenic bacteria invade the
dentinal tubules, demineralizing sclerotic and
peritubular dentin in the process
Current concepts of the generation of dentinal pain
General position of afferent nerve endings in the
odontoblastic layer, the predentin, and the dentin
Od: odontoblastic layer, SP: substance P, CGRP: calcitonin gene- releated peptide, BV: blood
vessels, PAN: primary afferent nociceptor, SPGN: sympathetic postganglionic nerves
Substance P-
immunreactive nerve
fibers (Nf) and nerve
endings ( ) of the
odontoblastic plexus
beneath a pulp horn.
D: dentin
Potential mechanisms that lead to the sensitization of
primary afferent nociceptors (PAN)
Sensitization of primary afferent nociceptors (PAN)
by arachidonic acid (AA) cascade and phospholipase A-
aktivating protein (PALP)
The rate of pain also depends on the level of heat
exposure
Pain development: gate control theory
A: stimulator effect, SG: spinal ganglion, B: interneuron, T: transmitting neurons
Dentine hypersensivity
Treatment
• To obliterate tubules by deposition of calcium salts
• To block tubules by protein precipitation
• To hyperpolarize or depolarize nerve fibers by altering ionic environment
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