DENTIN Flashcards
o greatest bulk of the tooth
o provides general form
o constitutes entire body of
the tooth
o located in both crown and
root
DENTIN
Physical properties of Dentin
- softer than enamel, harder than bone or root cementum
- yellowish intrinsic color
- physically firm, resilient or highly elastic and deformable
-more radiographically radioluscent than enamel, more radioopaque than pulp - positively birefingent - net effect of
superimposing optically positive collagen fibrils
and optically negative crystals - porous & permeable
Chemical properties of dentin
Chemically by weight is:
o approximately 70% organic material
o 20% inorganic material
o 10% water
Inorganic component
Hydroxyapatite in
the form of small
plates
Organic component
o about 90% collagen
(mainly type I with
small amounts of
types III and V)
o with fractional
inclusions of various
noncollagenous
matrix proteins and
lipids
Types of Dentin
o Primary
o Secondary
o Tertiary
o Predentin or Dentinoid
o Regular or Orthodentin
o Developed mostly before eruption
o Contains regularly arranged dentinal tubules
o Dentin formed up until conclusion of growth
o Forms bulk of the tooth
PRIMARY DENTIN
▪ the outer thin layer of
primary dentin
▪ the initial dentin formed
▪ 150 µm thick
▪ running parallel with the DEJ
▪ product of young, still
immature odontoblasts or
newly differentiated
odontoblasts
▪ lacks phosphophoryn
▪ slightly (4%) less mineralized
MANTLE DENTIN
o develops after root formation
o was once thought to form only in response to
functional stimuli – but found in unerupted teeth
o contains fewer dentinal tubules
o represents the continuing but slower deposition
of dentin after root formation
SECONDARY DENTIN
o Reactive, Reparative or Irregular Secondary Dentin
o Formed in response to outside or noxious stimuli:
* attrition, caries,
* erosion, cavity preparation
* therapeutic intervention
TERTIARY DENTIN
have vascular inclusion
VASODENTIN
similar bone
OSTEODENTIN
dentinal tubules are
formed by replacement
ATUBULAR DENTIN
- unmineralized or uncalcified dentin matrix
- variable thickness (10-47 micrometer)
- lines the innermost (pulpal) portion of the dentin
- similar to osteoid in bone
- consists principally of collagen, glycoproteins &
proteoglycans
PREDENTIN or DENTINOID
thickest where active dentinogenesis is occurring
its presence is important in maintaining the integrity
of dentin
when it is absent the mineralized dentin is vulnerable
to resorption of odontoclasts
PREDENTIN or DENTINOID
the line of directional change
the change from primary to
secondary or tertiary dentin
marked by abrupt changes in
tubular pattern
SCHREGER’S LINE
STRUCTURAL ELEMENTS OF
DENTIN
- Dentinal Matrix
- Dentinal Tubules
intercellular material of dentin consists of 2
fundamental units
Dentinal Matrix
2 Fundamental units of the dentinal matrix
FORMED ELEMENTS composed of collagenic
UNFORMED ELEMENTS—ground substance
imaginary fibers
associated with dentin caused by the silver
staining of ground substances
ALPHA OR KORFF”S FIBERS
BETA FIBRILS
fibrous
UNFORMED ELEMENTS—ground substance
MUCOPOLYSACCHARIDES
Parts of Dentinal Matrix
Intratubular Dentin
Intertubular Dentin
dentinal matrix that
covers the walls of the
dentinal tubules
* very dense
* has more appatite
crystals per unit volume,
uniformly mineralized
Intratubular Dentin
dentinal matrix located
between the dentinal
tubules
* the main bulk of the
dentinal material
* less densely mineralized
* noticeably less
radioopaque than
peritubular dentin
Intertubular Dentin
o inner organic
lining of
calcified tubule
walls
o high in
glucosaminogly
cans (GAG)
LAMINA LAMITANS
- cuspal – straighter in
course - proximal of crown – S shaped (crowding of
odontoblasts)
o primary curvature –
coronally
o secondary curvature
– apically - radicular – right angle
to long axis
radicular & cuspal - curvature is
much less pronounced (less Sshaped)
Dentinal Tubules
CONTENTS OF THE
DENTINAL TUBULES
ODONTOBLASTIC PROCESS S (TOME’S FIBER, DENTINAL FIBER)
PERIODONTOBLASTIC SPACE — DENTINAL FLUID
INTRATUBULAR NERVE
proteoglycans, tenascin, serum albumin, alpha-2 HS, and
transferrin and type V collagen - clearly a complex mixture.
- nonmyelinated nerve fibers of the trigeminal nerve
- extend up to 0.2 mm from the pulp
- occlusal dentin - approximately every other tubule
- pulp chamber – fewer
- cervical dentin - still fewer
INTRATUBULAR NERVE
Theories of Dentin Sensitivity
- TRANSDUCTION THEORY
2.DIRECT CONDUCTION THEORY - HYDRODYNAMIC THEORY OF
BRANNSTROM
The odontoblastic process mediates the transmission
of stimuli from the periphery of the dentin to the
nerve ending near the pulp
. TRANSDUCTION THEORY
The nerve endings near the pulp are stimulated
directly
DIRECT CONDUCTION THEORY
Suggests that transmission of
stimuli is added by a
movement of fluid within the
dentinal tubules or
odontoblastic process
HYDRODYNAMIC THEORY OF
BRANNSTROM
STRUCTURAL
CHARACTERISTICS OF DENTIN
- INTERGLOBULAR DENTIN
- GRANULAR LAYER OF TOMES
- INCREMENTAL LINES OF VON
EBNER - CONTOUR LINES OF
OWEN
- area of structural defect where
unmineralized or
hypomineralized dentin – fail
to fuse – homogenous mass - most frequent - circumpulpal
- prevalent in human teeth - a
deficiency in Vit. D or exposure
to high levels of fluoride at the
time of dentinogenesis
INTERGLOBULAR DENTIN
- structural defect that
- comprise uncalcified parts of the
ground substance - appear as dark (black) granules in
ground section - believed due to coalescing and
looping of the terminal portions
of the dentinal tubules - sensitive area
GRANULAR LAYER OF TOMES
- Is the phasic or increment of dentin
formation at the daily rate - approximately 4 micrometers
- represent the rhythmic process of
dentinogenesis - Run at right angles to the tubules
- Best seen in longitudinal sections
INCREMENTAL LINES OF VON
EBNER
- growth lines in dentin
- originally referred to a the
result of a coincidence of
secondary curvatures of
dentinal tubules - now applied also to
accentuated lines caused by
deficiencies in mineralization - neonatal line is a prominent
example
CONTOUR LINES OF
OWEN
orepresents an
accentuated growth
line that occurs
regularly in
deciduous teeth and
near occlusal
surfaces of
permanent first
molars
NEONATAL LINE
AGE CHANGES IN DENTIN
- Sclerotic Dentin or Transparent Dentin
- Dead Tracts
o Is the morphologic change
o includes thickening of the
peritubular dentin and
o complete obliteration of the
dentinal tubules
o 1
st mesial then distal of root
Sclerotic Dentin or Transparent Dentin
o Independent of age - can also
become sclerotic in locally
affected areas as a reaction to:
* abrasion
* attrition
* caries
* cavity preparation and
* application of corticosteroids
and filling materials
Sclerotic Dentin or Transparent Dentin
dentinal tubules are emptied
either by:
* complete refraction of the
odontoblastic processes
from the tubule or
* through the death of
odontoblasts
Dead Tracts
not seen clinically, only microscopically
* tubules are sealed off – in transmitted
light appear black in ground section
* disintegration may result from:
o Attrition
o erosion
o Abrasion
o caries and
o odontoblastic crowding
Dead
Tracts
