Dr. Saleem Shaikh
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Represent the interface between
two different mineralized
matrices.
Shallow depressions of Dentin fit
with the small projections of
Enamel.
Appears as a scalloped line.
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The irregular shape enables a
firm hold between enamel and
dentin.
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Before mineralization this is
known as the
‘Membrana preformativa’
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In the region of cusps and
incisal edges, the enamel rods
are vertical and tend to be
more wavy, irregular and tend
to interwine with each other.
This is referred to as gnarled
enamel.
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This arrangement of rods
makes the enamel stronger to
withstand masticatory forces
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These are alternate dark and light 
bands seen in longitudinal ground
section under reflected light.
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Enamel rods have a wavy course
from dentinoenamel junction to the
surface. When the tooth is sectioned,
some rods are cut longitudinally and
some are cut transversely
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Longitudinally – dark – parazones
Transversely – light – diazones.
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The change in direction of rods is
responsible for the appearance of
H-S bands.
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The incremental lines of retzius appear as brownish bands in
ground sections of enamel. They demonstrate the deposition of
successive layers of enamel during formation of crown.
Resemble growth rings on a tree
They are usually hypomineralized, may be hypermineralized also.
They represent 6-11 day rhythm in enamel formation
NEONATAL LINE: the enamel of some teeth forms partly before
birth and partly after birth. The boundary between these two types
of enamel is formed by an accentuated incremental line known as
Neonatal line
This line is seen in all deciduous teeth and first permanent molars.
Prenatal enamel is usually better developed than postnatal enamel.
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Perikymata are transverse,
wave like grooves seen on the
external tooth surfaces.
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They are the external
manifestations of straie of
retzius.
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Also known as Imbrication
lines of pickerill.
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They are thin leaf like structures
that extend from the enamel
surface towards the
dentinoenamel junction.
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These may be confused with
cracks which are caused by
grinding (delacification is used to
differentiate)
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May be site of weakness in the
tooth and may form a road of
entry for bacteria to initiate caries
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Three types of lamellae are seen –
type - A,B & C
Type A
Type B
Type C
Consists of
Poorly calcified
rod segments.
Degenerated cells
Organic matter
from saliva
Tooth
Unerupted
Unerupted
Erupted
Location
Restricted to the
Enamel.
May extend into
dentin
May extend into
dentin
Occurrence
Less common
Less common
More common
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Enamel tufts arise at the
dentinoenamel junction and
reach upto one third or one
fifth of its thickness.
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Enamel tufts are ribbon like
hypomineralized structures,
which occur in different planes
and are curving in different
directions. This creates an
impression of a tuft of grass.
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Maybe a result of adaptation to
spatial conditions of enamel.
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Small short rounded process
seen near the Dentinoenamel
junction.
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Because dentin forms before
enamel, the odontoblastic
processes occasionally crosses
the junction and enamel forms
around this process.
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Enamel spindles are
hypomineralized structures.
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Prismless surface layer of enamel: this is also known as the
structureless surface layer of enamel. In this zone no rods or
interrods are seen. It is slightly more heavily mineralized.
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Enamel Cuticle: Primary enamel cuticle (Nasmyth’s membrane) is
seen on the newly erupted tooth for some time, and is later lost due
to mastication. This resembles basal lamina and is secreted by the
ameloblasts.
erupted enamel is also normally covered by a layer known as
pellicle, which is formed by precipitation of salivary proteins. This
pellicle is removed during brushing of teeth and reforms within
hours. Within a day or two after the pellicle is formed it gets
colonized by microorganisms to form bacterial plaque.