4. The tooth proper consists of
the less mineralized, more
resilient and vital hard
connective tissue called
DENTIN
Orban’s oral histology and embryology 13th edition
Provides the bulk and
general form of tooth
It is characterized as a hard
tissue with tubules throughout
its thickness
5. It determines the shape of the crown , including the cups
and ridges ,and the number and size of the roots.
Physically & chemically the dentin closely resembles the
bone.
Orban’s oral histology and embryology 13th edition
11. Charactrized by start of mineralization
and root formation.
Formation of DENTINOENAMEL
JUNCTION
Formation of dentin occurs first
along this DEJ.
After first layer of dentin is
formed , amelobast lay down
enamel.
14. INDUCTION
• Epithelial cells are inductive
• secrete growth factors (TGF-B1
, BMP2, IGF)
• Binds to herpan sulfate found in
basal lamina
• Transferring inductive ability to
basal lamina
COMPETANCE
• Ectomesenchymal cells
assumes competance following
a set number of cell divisions
• After which they express cell
surface recpetors
• These receptors capture the
growth factors now localised to
basal lamina
15.
16. Once the odontoblast differentiate , they enter a life cycle
related to formation ,maintainance and repair of dentin.
The various stages of odontoblast are:-
Secretory stage
Resting stage
Transitional stage
17. Consist of
-Type 1 collagen
-Ground substance
ORGANIC MATRIX
First collagen of dentin appears:-
- Extracellularly
- Very distinct large diameter fibrils
Von Korff’s fibers
These large collagen fibers along with the ground substance
constitutes the organic matrix of First formed or Mantle dentin.
18. 18
Hydroxyapatite first appear
within the matrix vesicles as
single crystal
These crystals grow rapidly &
rupture from the confines of
vesicle
The deposition of mineral tags
behind organic matrix , so that
there is always a layer of organic
matrix PREDENTIN
INORGANIC MATRIX
19. .
first
• Increase size of odontoblast and organic matrix is now
formed exclusively from odontoblast
second
• Aggregation of collagen as much smaller fibrils,
which are more closely packed and interwoven
Third-
• Absence of matrix vesicles
Finally
• Addition of further components to organic matrix e.g.
Lipids, phosphoprotein , phospholipid
21. • Globular Pattern- Deposition of
crystals in several discrete areas
of matrix, these globular mass
continue to enlarge and fuse to
form single calcified mass.
• Linear Pattern- When the rate of
formation progress slowly, the
mineralisation front becomes
more linear and uniform.
22. Hertwig’s epithelial root
sheath intiate root dentin
formation.
• Less phosphoryn content.
Degree of mineralization
slightly less.
23. PHYSICAL PROPERTIES
It is light yellowish in color.
Orban’s oral histology and embryology 13th edition
It is viscoelastic and subject to
slight deformation.
Harder than bone but softer
than enamel.
It is more radiolucent than
enamel
25. By weight By volume
Chemical composition
Orban’s oral histology and embryology 13th edition
ORGANIC
20%
WATER
10%
INORGANI
C
70%
ORGANIC
33%
WATER
22%
INORGANI
C
45%
30. • First formed dentin underlying the
DEJ.
Orban’s oral histology and embryology 13th edition
•It is soft and provides cushioning
effect to tooth.
•The fibrils formed in this zone are
Von Korff’s fibers.
•Undergoes globular mineralization
31. Remaining bulk of primary dentin.
Orban’s oral histology and embryology 13th edition
Collagen fibrils are much smaller
in diameter (0.05 µm)
The mineralization pattern is
globular or linear for
circumpulpal dentin.
32. formed after root completion.
A narrow band of dentin bordering
the pulp
It is formed in response to external
stimuli
Clinical significance:- Protect the
pulp from exposure in older teeth.
Orban’s oral histology and embryology 13th edition
33. Also called as reparative , response, or reactive dentin.
It is formed in response to stimuli
- Attrition
-Abrasion
- Erosion
- Cavity preparation
Clinical significance:-
It is deposited at specific site in
response to injury
Orban’s oral histology and embryology 13th edition
36. The bodies of the odontoblasts are arranged in a layer
on the pulpal surface of the dentin, and only their
cytoplasmic processes are included in the tubules in the
mineralized matrix.
Orban’s oral histology and embryology 13th edition
37. Each cell gives rise to one process, which traverses the
predentin & calcified dentin within one tubule
38. The course follows a gentle curve in the crown, less so in
the root, where it resembles S in shape.
Orban’s oral histology and embryology 13th edition
39.
40. Canaliculi:-
The dentinal tubules have
lateral branches throughout
dentin, which are termed
canaliculi or microtubules.
Orban’s oral histology and embryology 13th edition
Enamel spindle:-
A few dentinal tubules extend
through the dentinoenamel
junction into the enamel. These
are termed enamel spindles.
41. Dentin permeability depends upon total surface area of exposed dentin.
Bacterial and their toxin products are the most significant to travel
down the tubules.
Heat or air desiccation eliminates fluid from tubules and thus increases
the dentin permeability.
The tubular structure of dentin also provides for rapid spread of dental
caries.
42. Orban’s oral histology and embryology 13th edition
Originally, the peritubular dentin is dentin
immediately surrounds the dentinal tubules.
It is 44nm wide near the pulp and 750nm
wide near the dentinoenamel junction
Rich in glycosaminoglycans termed Lamina
limitans.
43. Main body of dentin.
Location:- between the zones of
peritubular dentin.
Its organic matrix is retained after
decalcification.
About one-half of its volume is organic
matrix, specifically collagen fibers 0.2 to
0.5um diameter
Orban’s oral histology and embryology 13th edition
44. Location:- adjacent to the pulp tissue.
Is 2 to 6 um wide.
First formed dentin and
is not mineralized.
Orban’s oral histology and embryology 13th edition
46. Small globular areas that fail to
fuse into a homogeneous mass
called interglobular dentin.
The dentinal tubules pass
uninterruptedly, demonstrating
a defect of mineralization
& not of matrix formation.
Occurs more in cervical and middle
third of crown
Orban’s oral histology and embryology 13th edition
47. In dry ground section of root dentin, a zone adjacent to the cementum appears
granular in transmitted light.
Orban’s oral histology and embryology 13th edition
48. • It increases in amount from the CEJ to the
root apex
• Caused due to coalescing and looping of
terminal portions of dentinal tubules.
• High amount of calcium and phosphorus.
• Recent studies relate it as a special
arrangement of collagen and non
collagenous matrix proteins at the interface
between dentin and cementum.
Orban’s oral histology and embryology 13th edition
49. The incremental lines of von ebner, or imbrication lines,
appear as fine lines or striations in dentin.
Accentuated incremental lines because of disturbances in
matrix and mineralization process are termed as Contour
Lines of Owen.
Orban’s oral histology and embryology 13th edition
50. • In decidous teeth and first permanent molars the prenatal and
postnatal dentin are seperated by accentuated incremental
line termed as ‘Neonatal line’.
Orban’s oral histology and embryology 13th edition
51. • Scalloped line.
• The convexities of scallops are
directed towards dentin.
• More pronounced in occlusal
area where masticatory stresses
are greater.
52. • Smooth in outline.
• In deciduous teeth it may be
scalloped.
• The DCJ is a wide zone
containing large quantities of
collagen along with chondroitin
sulphate and dermatan sulphate.
53. • Nerve fibers accompany 30 to
70% of odontoblastic processes
-intratubular nerves.
They are terminal processes of
the myelinated nerve fibers of
the dental pulp.
Synapse like relation between
the process and nerve fibers
were demonstrated
Orban’s oral histology and embryology 13th edition
55. Various age and functional changes are:-
1) Reparative dentin
2) Dead tracts
3) Sclerotic dentin
56. o Also known as tertiary or response dentin.
o Has fewer & more twisted tubules than normal
dentin.
o Sometimes, a combination of osteodentin &
tubular dentin is seen
o Odontoblasts lay down at a rate of 4 um/day
Orban’s oral histology and embryology 13th edition
57. In dry ground section, the odontoblast process
disintegrate and the empty tubules get filled with air.
Orban’s oral histology and embryology 13th edition
58. Found specially in roots.
Transparent or light in transmitted and dark in reflected
light.
Orban’s oral histology and embryology 13th edition
59. Orban’s oral histology and embryology 13th edition
• In cases of stimuli such as caries , attrition causes
growth of collagen and apatite crystals begin appearing
in the dentinal tubules
• Apatite crystals are initially only sporadic in a dentinal
tubule but gradually fill it with a fine meshwork of
crystals.
• Gradually, the tubule lumen is obliterated with
mineral, which appears very much like the peritubular
dentin
61. • Autosomal dominant condition.
• Teeth appears Gray to yellowish brown.
• Broad crowns with constriction of cervical area results in
TULIP shape.
• Enamel is easily broken and leads to exposure of dentin.
63. Shield’s type III, Brandywine type DI.
Dentin is amber coloured and smooth.
Classic SHELL teeth are seen.
64. Bulbous crown, roots narrower ,pulp chambers
and canal smaller or completely obliterated.
Presence of ‘shell teeth’.
65. Dentin is composed of irregular tubules often with large
areas of uncalcified dentin.
Tubules are large in diameter in some areas & may also
be absent.
Pulp chamber is obliterated due to dentin deposition.
66. Directed primarily towards prevention of loss of
enamel and dentin by attrition.
Cast metal crowns on posteriors,
Jacket crowns on anterior teeth.
Restorations are not usually permanent because of
softness of dentin.
67. Normal enamel but atypical dentin formation and abnormal
pulpal morphology.
Radiographically, extremely short roots and obliteration of
pulp chambers and root canals
68. Radiographically:-
In deciduous teeth pulp chamber
and canals are
obliteratedwhile,crescent shaped
pulpal remnant seen in permanent
dentition.
Histologically:-
New dentin forms is Lava
flowing around the boulders.
69. Radiographically, deciduous
dentition shows obliteration of pulp
chambers while, permanent teeth
shows ‘Thistle tube’ appearance.
Histologically, atubular dentin in
deciduous teeth and numerous pulp
stones are seen in permanent teeth.
70. Maxillary teeth involved more
frequently.
Teeth are irregular in
appearance and shape is altered
markedly.
Evidence of defective
mineralization.
71. It shows marked reduction in radiodensity of teeth.
This is called as ‘Ghost’ appearance.
Enamel and dentin appear very thin and pulp chamber is
exceedingly large.
72. There is marked reduction in amount of dentin.
Widening of predentin layer
Presence of large areas of interglobular dentin and
irregular tubular pattern of dentin
Treatment: involves extraction and prosthetic
replacement.
73. Normal dentin is calcified by deposition of calcium salts in
the organic matrix in the form of globules.
In dentinal Hypocalcification there is failure of union in these
globules.
75. Caries in dentin begins with natural
spread of disease process along DEJ
and rapid involvement of large number
of dentinal tubules.
Which acts as pathway for micro-
organisms leading to dental pulp.
Dentinal caries advances more rapidly
in dentin than in enamel.
76. • Non bacterial, pre cavitational, Acid softening of
enamel
• Migration of pioneer bacteria along the tubules
• Breakdown of intervening matrix forming
liquefication foci
• Progressive disintegration of remainig matrix
tissue
77. • Deposition of fat globules
• Fat contributes to impermeability
ZONE1
• Deposition of calcium salts in tubules
• Appears white in transmitted light
ZONE 2
• Above the dentinal sclerosis
• Ocurs in advance of bacterial inavasionZONE 3
• Acidogenic organism in early caries
• Proteolytic organism in deeper layer
ZONE 4
• Necrotic mass of dentin of leathery
consistencyZONE 5
Zones of dentinal caries
79. Infected dentin Affected dentin
Outer carious dentin
soft and leathery in
consistency
Inner carious dentin
hard in consistency
dark brown in color. light brown in color.
high concentration of
bacteria
does not contain bacteria
collagen is irreversibly
denatured
Collagen is reversibly
denatured
not remineralised and
must be removed.
Can be remineralised and
therefore should
preserved
Infected and affected dentin
80. DEFINATION:-
It is defined as short , sharp pain arising from exposed
dentin in response to stimuli typically thermal,
chemical, tactile or osmotic and which cannot be
ascribed to any form of dental defect or pathology.
81. Direct Innervation theory
-Neural theory
-according to this theory , direct mechanical
stimulation of exposed nerve endings at DEJ is
responsible for dentin hypersensitivity.
Odontoblast Receptor theory
- tranduction theory
- it proposes that odontoblast itself act as neural
receptors and relay the signal to the nerve terminal
82. Dentinal tubules which are open and wide contains
fluid
Various stimuli displaces this fluid in either an
inwardly or outwardly direction
Movement of this liquid stimulates the odontoblastic
process
Subsequent mechanical disturbances stimulates
baroreceptors
Leads to neural discharge
89. The concept of dentistry with the introduction of adhesives has changed
from - Extension for Prevention to PREVENTION OF EXTENSION !!!
Adhesion of restorative materials to enamel has become a routine and
reliable aspect of modern restorative dentistry
But adhesion to dentin has proved to be more difficult and less predictable.
Much of the difficulty in bonding to dentin is the result of the complex
microstructure and variable composition of dentin in different areas of the
tooth.
90. The presence of water and organic components lower the surface energy
of dentin and make bonding with hydrophobic resins essentially
impossible
Dentin is an intrinsically hydrated tissue, penetrated by a maze of 1- to
0.25-μm-diameter fluid-filled dentin tubules.
Dentin close to the pulp shows a higher tubule density than in dentin
remote from the pulp. The higher the tubule density, the lower the bond
strength values of the dentin adhesives
91. Bonding agents can be defined as material of low viscosity, when applied
on the tooth surface forms thin film after setting.
This thin film strongly bonded to tooth surface, on which the viscous
composite restorative resin is applied. This sets forming an integrated resin
restoration.
92.
93. FIRST GENERATIONS
NPG-GMA, was the of first commercially available dentin bonding agent.
ADHESION TO SMEAR LAYER
SECOND GENERATION:-
Introduced in 1970s and bonded chemically to either inorganic or organic
components of dentin
But they produced only limited bond strength
(5-6 mpa)
Examples:-
Clear fill bonds system F
scotch bond
bond lite.
94. THIRD GENERATION
Third generation attempted to deal with smear layer and
dentinal fluid
They employed two approaches:-
Modification of smear layer to improve its property
Or
Removal of smear layer without disturbing smear plugs
that occlude the dentinal tubules.
The idea was to avoid aggressive
etching of dentin because it cause
pulpitis
Eg:- Tenure, Scotch bond2
95.
96.
97. Water acts as plasticizer for collagen and keeps it in a
soft state
If dentin is excessively dried it will lead to collapse of
collagen network
Critical amount of water is essential for bonding,
that prevents the collapse of collagen network
and allow expansion of dried dentin
An over wet dentin decreases the bond strength
and formation of blister like structure at the interface.
98. Most new adhesives utilize the
‘wet bonding technique’.
The ‘wet bonding’ has repeatedly shown enhanced bond
strengths as water preserves the porosity of collagen
network available for monomer interdiffusion.
99. whenever tooth structure is prepared with a bur or other
instrument, residual organic and inorganic components form
a layer of debris on the surface of the substrate
Smear layer fills the orifices of dentin tubules and form
smear plugs and decreases dentin permeability by nearly
90%
100. Thickness of smear layer : 0.5-2 μm
Thickness of smear plug : 1-10μm
COMPOSITION:-
Iatrogenically produced smear layer is predominantly
made of hydroxyapatite and altered denatured collagen.
Altered collagen acquire gelatinised consistency due to
friction and heat
101. CLINICAL CONSIDERATIONS
The presence of intact smear layer is detrimental for bonding
OPTIMAL DENTIN BONDING can take place
by:
a) Complete removal of smear layer prior to the bonding
procedure by using etch and rinse adhesive
b) Incorporation of smear layer into bonding layer by using self
etch adhesives.
102. Composite resin restorations
Early bonding agents were hydrophobic and were bonded
directly to dentin smear layer- Bond strength
unsatisfactory.
Newer bonding system leads to:-
a) Complete removal of smear layer prior to the
bonding procedure by using etch and rinse adhesive
b) Incorporation of smear layer into bonding layer
by using self etch adhesives.
103. Amalgam restorations
o Dentin smear layer are left in place for unbonded amlagam
restorations
o It produces some degree of dentinal tubule sealing ,
although it is 25 % to 30% porous
o Halving the diameter of the opening produces a sixteen fold
reduction in flow.
o Therefore the smear layer is very effective barrier.
104. ADVANTAGES :-
Reduction of dentin permability to toxins and oral fluids
Reduction of diffusion of fluid and prevents wetness of cut
dentin surface
Bacterial penetration of dentinal fluid is prevented.
105. It may harbour bacteria, either from original carious lesion
or saliva, which may multiply taking nourishmaent from
smear layer or dentinal fluid.
Smear layer is permeable to bacterial toxins
Smear layer itself is infected(Presence of bacteria)
It blocks antimicrobial effect of intracanal medications and
increases disinfecting tissue.
106. Presence of smear layer would necessitate use of higher
concentration and/ or amount of anti bacterial agents.
Act as a intermediate physical barrier, interfere with
adhesive penetration of sealers(obturating material)
with dentinal tubules
Studies have shown better adhesion of obturation
materials to the canal walls after removal of smear
layer.
107. CALCIUM HYDROXIDE
Herman (1930) – Ca(OH)2 pulp
capping
The greatest benefit of Ca(OH)2 is
the stimulation of reparative dentin
bridge formation.
Ex:- Pulpdent paste & Dycal
108. Biodentine is a new generation material based on calcium
silicate synthesized by bioactive technology
Biodentine stimulates release of TGF-β from pulpal cells,
stimulating reparative dentin formation in a very short period
of time.
109. COMPOSITE Shrinkage during polymerization may
induce internal stresses on dentin and create voids that
may lead to cuspal fracture and microleakage
110.
111. Type of restoration Shallow RDT
>2mm
Moderately
deep
RDT(>0.5-
2mm)
Deep RDT
<0.5mm
Silver
amalgam
varnish Base –e.g. zinc
phosphate , zinc
polycarboxylate
Calcium
hydroxide (sub
base) with base
Glass ionomer cement Not required Not required Calcium
hydroxide as
liner
Composite resin Dentin bonding
agent
Dentin bonding
agent
Calcium
hydroxide as
liner followed by
GIC as base
Cast restoration Base Calcium
hydroxide as
liner with base
over it
112. It is known that if 1mm.sq. of dentin is exposed 30,000
living cells are damaged.
So, it is advisable to seal exposed dentin surface with
non-irritating and insulating materials.
Preparation with rotary instruments is likely to injure
the odontoblastic layer.
Owing to dehydration of the tubular content,
odontoblasts may even be sucked into the
dentinal tubules.
113. Heat produced during deep cavity preparation causes loss
of odontoblasts or their aspiration into the dentinal
tubules. Thus, a coolant should be used while cutting
dentin.
Dessication during cavity preparation has long been
known to cause aspiration of odontoblastic nuclei into
dentinal tubules.
114. Periodontal diseases cause attachment loss exposing the
root surface to the oral cavity which may lead to
dentinal hypersensitivity.
115. If tetracycline is given in the period of pregnancy
or during the development of tooth, Then stains
are likely to be developed in the line related to
the dentinal curvature.
116. Ten cate oral histology (development structure and function)- 5th edition.
Orban’s oral histology and embryology- 13th edition.
Oral anatomy,histology and embryology : berkovitz.
Shafer’s textbook of oral pathology- 7th edition.
Sturdevent’s art & science of operative dentistry- 5th edition.
Grossman – 13th edition
Cohen pathology of the pulp 10th edition.
Editor's Notes
The main morphologic difference between bone & dentin is that bone is that odontoblast exist on the surface of bone and when one of these cells become entrapped it is called osteocytes, whereas the dentin contains only the processes of the cells that form it
Ectom cells closer to inner margins of enamel leads to formtn of dental papilla
Ectom cells closer to outer margins of enamel organ leads to formation of dental follicle
Dentin and pulp are derivatives of dental papilla
Pdl, cementum, alveolar bone are derivatives of dental follicle
-As the inavigination of epi continues , & its margin continue to proliferate the enamel organ assumesh bell shape.
-Crown shape is determined.
-4 different types of epithelial cell can be distinguished
IEE, ST. Intermedium, st. Reticulum, & OEE
IEE: consist of tall columnar cells called ameloblast, 4-5um in diameter, 40 um high
-st intermedium:- few layers of sq cells form the st intermedium, between iee & st. Reticulum
this layer is essential for enamel formation
-st reticulum:- before enamel formation begins these cells collapses reducingthe distance between ameloblast & nutrient capillaries
OEE- cells are flat to cuboidal
Dental papilla :-before IEE begans to produce enamel the peripheral cells of mesenchymal dental papilla deferentiate into odontoblast to produce dentin
The baseent membrane that seperates the enamel organ and dental papilla , just prior to dentin formation is called as membrane performative
The boundary between inner enamel epithelium and odontoblast outlines the future DEJ
The initiation of odontoblast diffetn involes the process of induction and competance
Tgf – trnasforming growth factor beta , BMP:- bone morphogenetic protein, IGF:- insulin like growth factor
Apart from this dentin formation is a connective tissue event
Before dentinogenesis, cells of internal dental epithelium are: Short and cuboidal, Rapidly dividing
Supported by basement lamina that separates the epithelium from dental papilla.
During odontoblastic differentiation:
Cell division ceases in the cells of the internal dental epithelium., Shape changes from short cuboidal to tall columnar. Reversal of polarity of the cell is seen
. Ectomesenchymal cells in dental papilla:- Rapidly enlarge to become preodontoblasts and then odontoblasts. Show increased amounts of RER and Golgi complex Nuclei are present away from internal dental epithelium.
Formation of organic matrix consist of type 1 collagen & associated ground substance
(0.1 to 0.2 µm in diameter)
to spread as cluster of crystallite that fuse with adjacent clusters to form fully mineralized matrix
Found between the odontoblast and mineralized front.
Once the layer of mantle dentin is formed the dentinogenesis occurs in slight different manner
One phosphoprotein – phosphophoryn is of particular intrest
It is highly phosphorylated protein unique to circumpulpul dentin and associated with mineralization.
lesser amount of it is found in root dentin
Also called as phenotypic marker for mature odontoblast
Depends upon the rate of dentin formation
Extra:- largest globules occurs where deposition is fastest.
When these globules fails to fuse , leaving area of uncalcified matrix knw as interglobular dentin
Rate of deposition is also slower
becoming darker with age.
This This elasticity provides flexibilty and prevents fracture of overlying brittle enamel.Thus, restorations like amalgam and inlays are always placed in dentin
It is soft and provides cushioning effect to tooth.
Outermost or peripheral part -20 µm thick.
The fibrils formed in this zone are Von Korff’s fibers.
Undergoes globular mineralization
Collagen fibrils are much smaller in diameter (0.05 µm)
The mineralization pattern is globular or linear for circumpulpal dentin.
Contains fewer tubules than prmary
Bend in the tubules where primary and secondary dentin interface
It is formed in response to external stimuli & protect the pulp from exposure in older teeth.
A-primary dentin
B- secondary dentin
C- teritary dentin
It is deposited on the pulpal surface of Dentin only in the affected area
S shaped configruation is due to oscillations of the odontoblast dictated by their crowding as the surface area they occupy decreases during their centripetal monement.
The first convexity of this doubly curved course is directed toward the apex of the tooth.
Near the root tip & along the incisal edges and cusps the tubules are almost straight.
Are perpendicular to the dentinoenamel and dentinocementum junctions.
Ratio between the outer and inner surfaces of dentin is about 5:1.
Ratio between the numbers of tubules per unit area on the pulpal and outer surfaces is 4:1.
. When 1mm of dentin is exposed 30,000 living cells are damaged
The calcified tubule wall has an inner organic lining termed the lamina limitans, high in glucosaminoglycans (GAG).
Highly mineralized
Lost in decalcified sections
As the collagen fibers undergo mineralization at the predentin- dentin front, the predentin then becomes dentin and a new layer of predentin forms circumpulpally.
The cytoplasmic extensions of the odontoblasts.
The odontoblasts reside in peripheral pulp and their processes extend into dentinal tubules.
Largest in diameter near the pulp and taper further into dentin.
The cell bodies are approx 7um in diameter and 40um in length.
Sometimes mineralization of dentin begins in small globular areas that fail to fuse into a homogenous mass. This results in zones of hypomineralization between globules
. followed by intercuspal and coronal third
Appears dark in transmitted light.
It increases in amount from the CEJ to the root apex.
It is caused by coalescing and looping of the terminal portions of the dentinal tubules
They run at right angles to the dentinal tubules.
These lines reflect the daily rhythmic, recurrent deposition of dentin matrix.
The course of the lines indicates the growth pattern of the dentin.
Reflects abrupt change in environment that occur at birth.
The dentin formed prior to birth is usually of better quality.
It is zone of hypocalcification.
The convexities of scallops are directed towards dentin.
More pronounced in occlusal area where masticatory stresses are greater.
If by extensive abrasion, erosion, caries, or operative procedures the odontoblast processes are exposed or cut, the odontoblasts die or, if they live, deposit reparative dentin.
Origin of the new odontoblast is from undifferentiated perivascular cell.
This the tubules appear black in transmitted light and white in reflected light.
Decreases sensitivity.
The reparative dentin seals the pulpal end of tubule and gas or fluid gets entrapped leading to dead tracts formation.
In cases of caries, attrition, abrasion, erosion or cavity preparation,stimuli causes growth of collagen and apatite crystals begin appearing in the dentinal tubules.
Incidence is 1 in 6000-8000 children
Brandywine type – this was found in brandywine triracial isolate in southern maryland
Crowns wear rapidly after eruption and multiple pulp exposure occurs.
Deciduous teeth show large pulp chambers while, in permanent teeth they are obliterated.
Acc to MACDOUGALL et al , stated that manifestation of di-2 can differ from di -1 by presence of multiple pulp exposure , a normal nonmineralized pulp chamber and general apperance of shell teeth.
Shell teeth:- have large pulp chambers , insufficent coronal dentin and usually no roots
Autosomal dominant condition with a rare disturbance of dentin formation characterized by normAal .
Early tooth mobility.
c/f :- delayed eruption
extreme mobility and are commonly exfoliated prematurely
The factors such as parathyroid deficiency or rickets could produce Hypocalcification
because dentin provides much less resistance to acid attack because of less mineralized content
Widening of tubules by demineralization
Distortion of tubules by expanding masses of bacteria
ZONE OF FATTY DEGENERATION
ZONE OF DENTAINAL SCLEROSIS
ZONE OF DECALCIFICATION OF DENTIN
ZONE OF BACTERIAL INVASION
ZONE OF DECOMPOSED DENTIN
-according to this theory , direct mechanical
stimulation of exposed nerve endings at DEJ is
responsible for dentin hypersensitivity.
Proposed by brannstorm
, due to a high alkalinity, which leads to enzyme phosphatase being activated and thus releasing of inorganic phosphate from the blood (calcium phosphate) leading to formation or dentinal bridge
Particular growth factors from the TGF-ß family have the ability to initiate odontoblast differentiation and hence produce tertiary dentine by cell signalling