Bài giảng nha khoa Dentin pulp complex

DENTIN-PULP COMPLEX:
STRUCTURAL BIOLOGY AND ITS APPLICATION
IN RESTORATIVE DENTISTRY

People’s Teacher
Prof. Hoàng Tử Hùng, DDS, PhD
E:
Website: hoangtuhung.com


INTRODUCTION
Dentin and dental pulp are differences in structure and composition:
• Dentin is a hard tissue
• Dental pulp is a soft tissue
Dentin and dental pulp have a common embryonic origin: ectomesenchyme
They remain in intimate relationship throughout the life of the vital tooth
Pulp and dentin are integrally connected in the sense that physiologic and pathologic
reactions in one of the tissues will also affect the other.
Anything that affects dentin will affect the pulp and vice versa
🡪 The concept of a dentin-pulp complex [or organ] is, therefore, well founded and
generally recognized
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CHARACTERISTICS OF DENTAL-PULP TISSUE
Most pulpal cells are considered to be of an undifferentiated or immature type.
They are abundant in newly erupted teeth and have the potential to differentiate
into specialized cells, e.g., odontoblast-like cells.
Pulpal physiology under normal conditions, and especially during inflammatory
responses, is dependent on interactions among cells, the blood and lymphatic
vessels of the pulp, the interstitial fluid, and nerves. Macrophages are seen in the

normal pulp, and their numbers increase in association with pulpal injury.
The interstitial fluid surrounds the morphologic elements is an important
intermediary link between cells, blood plasma, and lymph fluid. The interstitial
fluid of the pulp and the dentinal tubules form a continuum that extends from the
dentinoenamel and cementodentinal junctions to the central parts of the soft
connective tissue in the pulp.
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The structural characteristics of blood vessels in the
pulp include:
- thin walled,
- discontinuities in the endothelial walls, and
- fenestration of capillaries
Characteristics of the blood vessels have a
physiologic function: they facilitate the exchange of
nutrients and waste products between the
interstitial tissue fluid and the blood plasma.
This exchange is particularly important at the time
of injury, including operative procedures, trauma,
and caries lesions affecting the pulp.
Lymphatic vessels transport fluid out of the pulp
and
play a role in maintaining the fluid balance.
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DENTIN SENSITIVITY
Dentin-pulp complex is a sensitive organ. The exposed dentin is especially sensitive.
All stimuli: pressure, trauma, heat, cold and chemical irritation etc. are perceived as

some form of discomfort or “pain”
Cold stimuli were found to be more painful than hot stimuli, probably because of
the outward fluid flow that results from shrinkage of the contents of the tubules
when cold is applied.
When heat is applied, the contents of the tubules expand and an inward flow
occurs.
Typical dentin pain is short-lasting, sharp, and may be described as lancinating.
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Three mechanisms have been proposed to explain
dentin sensitivity:
1- the direct innervation theory: dentin is
innervated directly: dentin contains nerve endings
that respond when it is stimulated
2- the transduction theory: odontoblast serve as
receptors and are coupled to nerves in the pulp.
- The odontoblast receptor theory: intercellular
odontoblast-neuron signal transduction
3- the hydrodynamic theory (by Brännström): the tubular nature of dentin permits
dentin fluid movement to occur within the tubule when a stimulus is applied, a
movement registered by pulpal free nerve endings close to the dentin
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Any reduction in conductance will reduce the
dentin sensitivity:
- by occlusion of the tubules by mineral
precipitation, adsorption of organic materials in
the tubules, or

- by hypermineralization of the surface dentin.
The formation of peritubular dentin at the
interface between primary or secondary dentin
and tertiary dentin will also reduce the
conductivity of dentin fluid.
Agents that prevent the contents of the tubules
flux across exposed dentin may eliminate or
reduce dentin pain. This is applied in treatment
of dentinal hypersensitive products and the
contemporary dentin adhesive techniques
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Opened dentinal tubules (Dt) and
naturally desensitized erea: the Dt are closed


Interstitial fluid and Interstitial fluid pressure
The interstitial fluid pressure in the pulp is
relatively high, and it plays a role in the
sudden pain experienced when a cavity
preparation reaches unaffected dentin.

Chemically, pulp tissue: 25% organic and 75% water
The pressure: 8 – 15 mmHg
With pulpal inflammation, the pressure can rise to 35 mmHg or higher, the pulp
almost totally enclosed within a hard tissue chamber, can quickly suffer
irreversible damage.
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AGING TOOTH AND DENTIN-PULP COMPLEX
The dentin-pulp complex undergoes regressive change with time
− Progressive narrowing of the pulp cavity [secondary &
tertiary dentin]
− Deposition of intratubular dentin continues, resulting in a
gradual reduction of the tubule diameter and event
complete closure
The fiber-poor and cell-rich state is a characteristic feature of
the young pulp, but it changes with age:

Narowing of the pulp
cavity, Translucent dentin,
Depositon of cementum

- Reduction in the number of blood vessels
- Gradual decrease in the concentration of fibroblasts
within the coronal pulp
- Gradual increase of collagen fiber bundles within the root canals
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Age-related changes in the pulp nerves and blood vessels accompany the
cellular changes:
In the pulp of older individuals, a large fibrous component is present and the
number of cells is low.
Clinically, this change is important because progenitor cells are available to
differentiate into other cell types or to take part in reparative processes in the
pulps of young patients are less effective in the pulps of the elderly.

Tissue in the central part of the pulp in a newly erupted

tooth: the large number of cells (left) and a 67-year-old
individual: few cells are found.
BV = Blood vessel (x350 )
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An aging pulp tissue loses some of its functional capacity:
• Degeneration of axons that correlated reduction sensitivity
• Ability of the pulp-dentin complex to repair itself
• Appearance of irregular areas of dystrophic calcification
Formation of pulp stones (or denticles): discrete calcified masses of calcium
–phosphorus. They may be singular or multiple and found usually at orifice of
the pulp cavity.
Physiologic aging changes of the dentin-pulp complex can be troubled or stopped
by chronic pathological processes: caries, pulpitis, trauma, and especially pulpal
necrosis.
Age changes in the pulp-dentin complex render it more resistant to environmental
injury:
- The spread of caries is slowed by tubule occlusion
- Less sensibility in response to stimuli
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DENTIN “WOULD” and PULPAL IRRITATION
≈ 30% volume of dentin is taken up by cytoplasm of the
odontoblastic processes and their lateral branches
≈ 30 000 – 40 000 odontoblastic processes are cut for
every mm² of dentin during classic box cavity preparation
Crown preparation, which end in the peripheral
zone of dentin, open ≈ 15 000 tubules/1 mm²

The danger is reduced with aging tooth because of
secondary dentin formation, reducing size of pulp chamber
and sclerosis of the dentin
This close association includes reactions to caries and common clinical
procedures such as cavity or crown preparations and restorative procedures.
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DENTIN-PULP COMPLEX RESPONSE TO RESTORATIVE PROCEDURE
A biologic approach to restorative dentistry requires knowledge of the normal
structure and physiology of dentin and pulp, including age-related changes.
All components of the dental pulp, including the cells, blood and lymphatic vessels,
nerves, and the interstitial fluid, are important in the response to restorative
procedures.
Hydrodynamic effects and fluid shifts are, therefore, important under normal and
pathologic conditions and they will affect the pulp-dentin organ.
The mere cutting of dentin, as it occurs during cavity and crown preparations, will result
in several of reactions in the pulp and the dentin.
Pulpal pain is characteristically pulsating, long-lasting, and of variable severity, sometimes
excruciating. It is also affected by changes in blood pressure to the bead.
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PULPAL
IRRITATIONS
Protection of the vitality of the pulp is paramount goal of all restorative procedures
Every dentin intervention that involves opening of dental tubules brings a
reaction in the pulp tissue. Tissue damage and reactions may be reversible or
irreversible
The type, duration, and severity of the pulp reaction will vary depending on the

type of irritations produced by technical factors and:
- cavity preparation, [physically, temperature and pressure reached during]
- chemically, materials that use for dentin and enamel etching [acidic
solutions]
- bonding agent
- filling material
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Agents that prevent the dentin tubular contents flux across exposed dentin may eliminate
or reduce dentin pain

A smear layer is an adherent layer of debris on
tooth surfaces when they are cut with rotary or
hand instruments
The orifices of the dentin tubules are
obstructed by debris tags, called smear plugs,
which may extend into the tubule to a depth of
1–10 mm. These smear plugs are contiguous
with the smear layer.
In dentin bonding procedures, a hybrid layer is created
in which resin infiltrate into smear layer and smear
plugs of dentin
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MECHANISM OF DENTIN BONDING

A smear layer of ≈ 1 μm
covers the entire dentin

surface, and a smear plug,
extending 1 -10 μm into the
dentin tubule, occludes the
tubule’s orifice.

Dentin etched with 37.5%
phosphoric acid. At the dentin
surface and tubule walls, the
inorganic component of dentin
smear and peritubular dentin has
been dissolved, resulting in the
typical funneling of the tubule
orifice.
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With the infiltration of
resin into smear layer, the
hybrid layer is created on
dentin surface and resin
tags extend into the
dentinal tubules, attaching
the resin tags to tubules
walls.


PULPAL IRRITATIONS (cont’d.)
Temperature increases greater than 10ºC cause precipitation of protein and
irreversible cell and tissue necrosis

During cavity preparation with rotary instruments,

the stream of coolant (spray) should be reaching the
site
Autopolymerization of acrylic resin in situ
[temporary crown, anterior jig…] can rise the
temperature in the pulp chamber to 75ºC
In the worst case, the odontoblastic layer becomes
devitalized over a large area
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Summary
From a functional point of view and especially in relation to restorative dentistry,
dentin and pulp are integrated to an extent that they should be regarded as
a complex.
A biologic approach to restorative dentistry requires knowledge of the normal
structure and physiology of dentin and pulp, including age-related changes.
Protection of the vitality of the pulp is paramount goal of conservative dentistry
All restorative procedures in a vital tooth should prevent the damage to the
dentin-pulp complex
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SUCGESTED READING
- Shibukawa Y, Sato M, Kimura M, et al.: Odontoblast as sensory receptors:
transient receptor potential channels, pannexin-1, and ionotropic ATP receptors
mediate intercellular odontoblastneuron signal transduction, Pflugers Arch, 2014
- B.K.B Berkovitz, G.R. Holland, B.J. Moxham: Oral Anatomy, Histology and
Embryology, Mosby, 2002
- A. Nanci: Ten Cate’s Oral Histology, Mosby, 6th ed., 2003

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