Tiber- Enamel

Front 1

What controls the growth of enmael prisms?

Back 1

Amelogenins

Front 2

What regulates the pattern of enamel prisms

Back 2

Inner enamel epithellium

Front 3

What constitutes prism type enamel?

Back 3

Enamel prisms, interprismatic enamel, and prism sheaths

Front 4

Of what thickness of enamel do you enamel prisms run? where do they increase in diameter? What is their average diameter?

Back 4

Entire thickness.
Prisms increase in diameter in direction of enamel surface, with average diameter of enamel prisms at 4-6um.

Front 5

How are the terminations of enamel prisms oriented?
How about in transverse plane?

Back 5

Perpendicular to the DEJ, and perpendicular to a tangent to the enamel surface.

In the transverse plane, the enamel prisms trace a waveshaped path in the inner 1/2 of the enamel thickness, and a straight path in the outer enamel.

Front 6

True/ False
Keyhole-shaped prisms display a "head" region and a thin “tail" region,in an occlusoapical direction, respectively.
Round-shaped prisms are ringed by a region
of enamel called interprismatic enamel which, in transposition, becomes the "tail" region
in the keyhole-shaped construct of prism morphology.

Back 6

True.

Front 7

During what phase do enamel crystals grown in length?
During what phase do matrix proteins degrade?

Back 7

Enamel crystals grow in length during the secretion phase, embedded in a protein
matrix.! During the maturation phase, shown above in an electron micrograph, the
matrix proteins degrade, and the crystals grow in thickness and width until most of
the space between the tissues is occupied by mineral.

Front 8

At what border is the prism sheeth present? how thick is it?

Back 8

prism sheath is present at the occlusal border of each enamel prism where the
crystallites of the prisms and the crystallites of the adjacent enamel subunits (i.e., "tail"
regions/interprismatic regions) display a distinct divergence in orientation. The prism
sheath is about 0.1 to 0.3 um thick and has a marginally higher organic content than the
prism it borders due to the spread of divergent enamel crystallites.

Front 9

Describe the properties of the rod striations?
Do they grow? If so, how much?

Back 9

Rod Striations. Rod striations mark the daily increments of enamel growth, about 4
to 6 um per day. Investigators have proposed that the rod striations are manifestations
of either a periodic change in the width of the enamel prisms along their length (i.e.,
varicosities), or low amplitude undulations of the enamel prisms in the vertical axis (Fig.
4). Others have hypothesized that the rod striations reflect the interprismatic regions
related to rods cut at angles.

Front 10

Describe the properties of the incremental lines? (striae) of retzius?
hypo/hyper mineralized? How long is the secretion? How do they appear in light microscopes? in longitudinal sections?

Back 10

In light microscopy, the lines of Retzius
appear as brown-colored bands of varying widths in ground sections of enamel (Fig. 5a,
5b, 9). In longitudinal sections, the lines of Retzius are arranged in concentric arcs, some
of which run to the enamel surface, and some of which are contained within the enamel
over the incisal edges and cusp tips. In transverse sections of the tooth the lines are
arranged in concentric circles (Fig. 5a}. The lines of Retzius are zones of
hypomineralized enamel which are secreted over a period of days to weeks. Some
enamel prisms take a sharp turn in direction within the lines of Retzius.

Front 11

Where is the neonatal line present? hypo/hyper?

Back 11

A neonatal line is present in the deciduous dentition and in the first
permanent molar teeth. "Neonatal enamel" is relatively poor in quality, reflecting
peripartum metabolic disturbance. The neonatal line may be considered to be an
exaggerated line of Retzius, and the enamel prisms within this growth line are often
hypomineralized and change direction.

Front 12

What is the orientation of enamel lamella? Where does it extend until? When does it come into play? properties?

Back 12

An enamel lamella is a longitudinally oriented, ribbonlike structure which extends
from the dentinoenamel junction through the thickness of the enamel (Fig. 6d). It arises
during amelogenesis and is filled with organic material which remains intact after acid
demineralization of the enamel. Enamel lamellae must be differentiated from enamel
cracks which may arise pre- or posteruptively, and which also are filled with organic
material.

Front 13

What is the orientation of enamel tufts? histplogically? How far do they extend?
Hypo/Hyper?

Back 13

Enamel tufts are branched, longitudinally oriented, ribbonlike structures (Fig. 6a,
6b, 6c). In histological sections, they resemble blades of grass that grow out of a
common root. Enamel tufts extend from the dentinoenamel junction into about onethird
the thickness of the enamel. Enamel tufts are hypomineralized structures which
appear to coincide in position with prism sheath zones.

Front 14

Developmentally, enamel spindles mark sites where odontoblastic processes extend between the
ameloblasts during odontogenesis and subsequently become embedded in the nascent
enamel matrix.

T/F?

Back 14

True,
An enamel spindle is the terminal segment of a dentinal tubule that extends a short
distance across the dentinoenamel junction into the enamel (Fig. 7a, b). In ground
–4–
sections of a tooth, enamel spindles are filled with air and debris. Developmentally,
enamel spindles mark sites where odontoblastic processes extend between the
ameloblasts during odontogenesis and subsequently become embedded in the nascent
enamel matrix.

Front 15

What time of enamel appear to spiral each other within cusp regions of enamel? qhy?

Back 15

In longitudinal ground sections of teeth, groups of enamel rods appear to spiral
around each other within the cusp regions of the enamel. Such enamel is termed
gnarled enamel. This configuration of enamel rods was believed to strengthen the
resistance of the enamel to fracture, however, gnarled enamel is likely an image
imprinted when viewing the wave-shaped prism paths of the enamel prisms through
several superimposed layers of prisms.

Front 16

What type of enamel appears as light and dark bands which run from the DEJ to halfway or 4/5ths through the width of the enamel?

Back 16

Hunter-Schreger bands are observed in longitudinal ground sections of teeth
viewed with incident light (Fig. 8). They appear as alternating light and dark bands
which run from the dentinoenamel junction to about halfway to four-fifths through the
width of the enamel. Hunter-Schreger bands are the optical effects of the reflection or
absorption of light waves by the wave-shaped enamel prisms in the inner half of the
enamel.

Front 17

___________ appear in young teeth as an overlapping arrangement of parallel
troughs and ridges that are visible on the enamel surface

Back 17

Perikymata appear in young teeth as an overlapping arrangement of parallel
troughs and ridges that are visible on the enamel surface (Fig. 5c, 9). The perikymata
are aligned in the transverse plane and are more numerous and closely spaced in the
cervical region of the crown. The troughs of the perikymata coincide in position with
the terminations of the lines of Retzius at the enamel surface (Fig. 9). The perikymata
become less prominent or nonexistent in middle aged people due to tooth-brush
abrasion of the surface enamel.