L5

Question 1

Of the 4 tissues of a tooth, enamel is only one that is not a

Answer 1

connective tissue; it’s

an ectodermal derived tissue and formed by a specialized epithelial cell (ameloblast)

Question 2

Of the 4 mineralized tissues, enamel is the only one that does
not have an

Answer 2

unmineralized or preenamel formation stage:

enamel has an immature stage (partially mineralized) and a mature stage (fully mineralized)

Question 3

Enamel is the second

Answer 3

mineralized tissue to appear in a developing tooth,

dentin is the first to appear:

Question 4

Enamel is subject to

Answer 4

malformations (genetic and external factors), age changes,

self-induced habits

Question 5

Enamel has unique

Answer 5

organic substance, unlike the other 3 mineralized tissues,

does not contain collagen fibers

Question 6

Hardest and most highly

Answer 6

mineralized biological tissue

As hard as mild steel

Question 7

Hue depends on:

Answer 7

location level, surface conditions of enamel,

attraction to stain substances, and age changes

Question 8

Enamel Needs a

Answer 8

wet environment to maintain its integrity

Question 9

Micro porosity:

Answer 9

pathways for diffusion of small molecules
such as water:
electrochemical effects on pore walls lead to carious lesions

Question 10

Organic substance:

Answer 10

1% by weight.
Types of unique proteins: Amelogenin (main) and
non-amelogenin (enamelin, amelin, tuftelin (and others ??)
Highest percentage (90 %) of the organic substance of enamel
is composed of amelogenin: a seed protein for normal mineralization
Enamel proteins are arranged in a lace like pattern throughout the volume
of enamel and closely associated with the surface of the crystals

Question 11

Note: enamel is the only one of the 4 mineralized tissue that does
NOT contain

Answer 11

collagen fibers

Question 12

Water:

Answer 12

3% by weight:
distributed throughout the volume of enamel by way of micropores
between crystals and proteins:
most of the water forms a hydration shell around each crystal:
Its distribution is of clinical importance: route of: fluoride ions: calcium and phosphorous ions
for remineralization: whitening substances artificial and natural substances:
acidophilic microorganisms: age changes……..

Question 13

CEJ: relationships

Answer 13

1 = most common: cementum (C) overlaps enamel (E)
2 = next common: cementum meets enamel
3 = least common: cementum does not meet enamel

Question 14

Growth lines of enamel:

Answer 14

lines or strae of Retzius

Question 15

Perikymata are numerous small

Answer 15

transverse ridges on the exposed
surfaces of enamel
Striae or lines of Retzius end on the enamel surface as grooves,
ridges (perikymata) are created between the grooves.

Question 16

Each perikyma is thought to 
take approx. 8 – 10 days to 
form and thus the count of 
perikymata may be used to 
assess how long a

Answer 16

tooth crown

took to form.

Question 17

Perikymata can be found on all permanent teeth, but are usually most noticeable on

Answer 17

canines

Question 18

Enamel rods:

Answer 18

Structural unit of enamel
A rod has a diameter of 5-6 μm and a length of up to 2.5 mm.
Several million crystallites are packed in each rod
Hydroxyapatite crystals are most dense in the center or core of the rod and run parallel to the long axis
of the rod
Note: Each rod is formed by one ameloblast

Question 19

Enamel sheath (?)

Answer 19

Outer surface of the rod
Crystals are less dense than those of core and run in different directions, higher % of organic
substance
Here, the highest percentage of organic material is amelin

Question 20

Interrod substance

Answer 20

Between the sheaths of the rods
Crystals are more dense and run at different directions than those of the sheath
Note: Two or more ameloblasts secrete the interrod substance

Question 21

Each ameloblast secretes

Answer 21

one rod and its sheath

Question 22

Two or more ameloblast secrete the

Answer 22

interrod substance ( I

Question 23

Enamel lamella

Answer 23

Lamellae, extend for varying depths from the surface of enamel and consist of
longitudinally oriented defects filled with enamel protein or organic debris
from the oral cavity:
Clinical significance: due to their access by acidophilic microoranisms (caries)
and to stain substances (esthetic considerations)

Question 24

Enamel tuft:

Answer 24

Tufts project from the dentinoenamel junction for a short distance into enamel
and contain greater concentration of enamel protein (tuftelin):
Clinical significance: contributes to the spread of caries at the DEJ

Question 25

Enamel spindle:

Answer 25

Spindles extend from the dentin cross the dentinoenamel junction into
the enamel for a short distance:
Clinical significance: contributes to the spread of caries along the DEJ

Question 26

Hunter-Schreager bands:

Answer 26

Alternating dark and light bands (layers) of varying width: Originate at the DEJ border and pass outward ending at some distance from the outer enamel surface: Caused by the different direction of enamel rods in adjacent layers.
This change in rod direction is regarded as a functional adaptation, minimizing the risk of cleavage in the axial direction under the influence of masticatory forces. And clincally significant when performing operative dentistry

Question 27

Differentiation of the inner epithelial cells of the enamel organ into ameloblasts and of the peripheral cells of the dental papilla into odontoblasts begins in the

Answer 27

coronal most site of the future dentinoenamel junction