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86 Cards in this Set

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  • Back
What is the hardest substance in the body?
enamel
Enamel is (cellular/acellular) and is mostly devoid of ____________.
acellular, organic material
What accounts for 96% of enamel?
hydroxyapatite
What are the percentages of water and organic material in enamel?
3%; 0.5-1%
10% HCl will result in _____________ of the enamel?
decalcification
What is the basic structural unit of enamel?
enamel rods
The organic component of enamel is what percent protein?
90-95%
What are the two major proteins in enamel?
enamelin and amelogenin
Ground substance of enamel is composed of what three substances?
1. polysacchrides
2. glycoproteins
3. phospholipids
the length of an enamel rod depends on its location in the ___________?
crown
T or F: the length of an enamel rod may exceed the thickness of the enamel
true
average enamel is rod is ________ in length and __________ in width?
2mm, 5um
rods are thicker towards the (surface/DEJ)?
surface
What portion of the enamel rods are wavy?
first 1/3 of the enamel rods (near DEJ)
enamel rod density is higher at the DEJ or surface of the tooth?
DEJ
Daily deposition of enamel results in what structure?
cross striations
a cross section of an enamel rod has what shape?
key-hole
enamel rods consist of what two regions?
head and tail
enamel rod sheaths are distinct around _____________ but blurred around _____________?
the head, tails
enamel rods are (parallel/perpendicular) to the long axis of the tooth, while interrod enamel is (parallel/perpendicular).
parallel, perpendicular
Interrod enamel is (more/less) mineralized than enamel rods.
less
Lack of a Tome's process will result in what kind of enamel?
prismless
Tome's process pit produces the rod _______?
head
__ ameloblasts make a core, but __ make a tail?
1,3
____________ is randomly dispersed the a tome's process while ___________ is not.
amelogenin, enamelin
_______________ serves as a template for HA deposition in enamel?
enamelin
T or F: maturation of enamel involves the addition in number of HA crystals?
False, number and length do not change, only width of the crystals.
Removal of what protein allows HA crystal to increase in size?
amelogenin
Name two places where prismless enamel occurs?
DEJ, surface
HA crystal in the enamel rod are arranged parallel to the _____________ of the rod.
long axis
HA crystals in the rod tail are arranged ____________ to the rod.
obliquely
Interrod enamel is located between a rod ______ and a rod ______?
head, tail
greatest amount of matrix in enamel is found in the _______________?
enamel rod sheath
enamel rod sheath is approx. _____ um in width?
0.2
The only way to distinguish between enamel rod head and rod sheath by determining the amount of ______________________?
matrix and calcification
Enamel rod ______ is almost exclusively HA crystals while the enamel rod _______ is almost exclusively matrix.
head, sheath
name the 3 zones of an enamel HA crystal.
1. hydration shell
2. crystal surface
3. cyrstal interior
The hydration shell on an HA crystal is formed on the outside of what layer?
crystal surface by incorporation of water
Which layer of an HA crystal interacts with ions?
crystal surface
Most ions which interact with the crystal surface of an HA crystal (soften/harden) the enamel? The exception is (Na, Mg, F, Sr, Ra, CO3, citrate)?
soften, F
An HA crystal is _____nm thick x ___nm wide x ____um long?
30,65,2
space between HA crystal is less than ___ nm?
2
Enamel runs ____________ at the DEJ, ____________ in the middle zone and ______________ in the outer zone.
perpendicular, helically, perpendicular
Enamel appears wavy in the 1/3 portion nearnest the (DEJ/surface of the tooth)?
DEJ
______________ are regions in enamel where groups of enamel rod curve up and out while others curve in and down.
Hunter Schreger bands
Hunter Schreger bands appear as ______ and _______ bands within the enamel.
light, dark
If you were to section a tooth longitudinally, what band would you see in the enamel? How would they appear?
Hunter Schreger bands; you would see some bands coming towards you and some running longitudinally
More organic content allows (more/less) light to penetrate the structure?
more
T or F: enamel lamellae extend the length of the enamel?
True
Enamel lamellae are ____________ mineralized enamel?
improperly
What are A, B and C?
A - lamella
B - tuft
C - spindle
Name the 3 causes of enamel lamella formation.
1. Uncalcified enamel
2. crack formed and filled with enamel organ cells (before eruption)
3. crack formed after eruption and filled with salivary proteins
T or F: enamel lamellae are more common with age?
True, due to unequal loading on teeth
T or F: enamel tufts extend the whole length of the enamel.
False, they extend only through the inner 1/3
Enamel tufts are (normal/abnormal) structures in enamel?
normal
Enamel tufts are (more/less) calcified than surrounding enamel?
less
Enamel tufts increase the organic content of enamel near the DEJ to _x other enamel?
3
Enamel tufts have a __________ appearance.
grass-like
"Leaves" of the enamel tufts are due to the _______________?
curvature of enamel in this region
Tension planes will cause (increased/decreased) calcification?
decreased
An enamel spindle is an ___________ ___________ that gets stuck in enamel.
odontoblastic process
DEJ is ____________ (shape) with (concave/convex) portion towards the DEJ?
scalloped;concave
The number of concavities in the DEJ roughly corresponds with the number of what?
enamel rods
cross striations are in (enamel/dentin)?
enamel
cross striations are (parallel/perpendicular) to enamel rods?
perpendicular
cross striations represent the ________ growth increment and are approx. __ - __ um apart?
daily; 4,5
Cross striations are synonamous with what what lines in dentin?
inbricaiton lines of von Ebener
Cross striations have dark and light lines. Dark lines represent areas of (more/less) calcification?
less
Stria of Retzius are due to _______?
stress
Stria of Retzius are formed because of a retraction of ______ ____________?
tome's process
Stria of retzius formed at birth is called a _________________?
neonatal line
Stria of retzius are (more/less) calcified than surrounding enamel?
less (dark = less)
Perikymata are surface manifestations of _____________?
stria of retzius
Perikymata are interspersed __________ and _______ and are located near the ______ of the tooth?
grooves, ridges; cervix
T or F: perikymata will eventually wear down?
True
T or F: Gnarled enamel is present near the DEJ?
False, it is found in cuspal regions
T or F: Gnarled enamel may extend through entire enamel region?
True
Gnarled enamel (strengthens/weakens) the tooth structure?
strengthens
Enamel in pits and fissures is (stronger/weaker) than at the cusps?
weaker
Ameloblasts often cannot complete maturation of the enamel in pits and fissures due to?
crowding and strangulation
Margins of restorations should be placed in (gnarled/non-gnarled enamel)?
non-gnarled (good luck!)
Precarious enamel lesions involve the dissolution of what part of the enamel?
crystal cores
In carious lesions the length of the enamel crystals is ____________ but it it isn't in precarious lesions.
shortened
Etching of enamel preferentially dissolves enamel rod ________?
head (core)
When enamel is etched, what can fill the areas of dissolved enamel?
restorative material (composite)
Etching will not roughen enamel surface where the enamel is ____________?
prismless