DENTIN Flashcards by ELIZA NICOLE ATA

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

Chemical properties of dentin

Chemically by weight is:
o approximately 70% organic material
o 20% inorganic material
o 10% water

How well did you know this?

Not at all

Perfectly

Inorganic component

Hydroxyapatite in
the form of small
plates

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

Types of Dentin

o Primary
o Secondary
o Tertiary
o Predentin or Dentinoid

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

▪ 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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

have vascular inclusion

VASODENTIN

How well did you know this?

Not at all

Perfectly

similar bone

OSTEODENTIN

How well did you know this?

Not at all

Perfectly

dentinal tubules are
formed by replacement

ATUBULAR DENTIN

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

 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

How well did you know this?

Not at all

Perfectly

 the line of directional change
 the change from primary to
secondary or tertiary dentin
 marked by abrupt changes in
tubular pattern

SCHREGER’S LINE

How well did you know this?

Not at all

Perfectly

STRUCTURAL ELEMENTS OF
DENTIN

Dentinal Matrix
Dentinal Tubules

How well did you know this?

Not at all

Perfectly

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

1. TRANSDUCTION THEORY 2.DIRECT CONDUCTION THEORY 3. 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

1. INTERGLOBULAR DENTIN 2. GRANULAR LAYER OF TOMES 3. INCREMENTAL LINES OF VON EBNER 4. 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

1. Sclerotic Dentin or Transparent Dentin 2. 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