Enamel Tissue Flashcards
Which tissue is the hardest of the 4 mineralized tissues of the body?
enamel
Of the 4 tissues of a tooth, which is the only that is NOT a connective tissue?
enamel
Enamel is derived from what tissue?
ectodermal derived tissued formed by a specialized epithelial cell - ameloblasts
Of the 4 mineralized tissues, enamel is the only one that does not have an ___ or ___ formation stage.
unmineralized; preenamel
T/F. Enamel has a immature stage (partially mineralized) and a mature stage (fully mineralized).
True.
T/F. The ameloblast completes its enamel formative cycle once the thickness of enamel is reached at a site (most advanced coronally).
True.
Enamel is the ___ mineralized tissue to appear in a developing tooth, ___ is the first to appear.
second; dentin
T/F. Enamel is not subjected to malformations (genetic and external factors), age changes, and self-induced habits.
False, Enamel IS subjected to malformations (genetic and external factors), age changes, and self-induced habits.
T/F. Enamel does not have enclosed cells (acellular), nerves (aneural), blood vessels (avascular), or lymph vessels (alymphatic).
True.
Which tissue is the most clinically significant?
enamel
What is the value for enamel on the Mohs mineral hardness scale?
5
Enamel can withstand ___ and impact forces well but is ___ without dentin support.
shearing; brittle
Enamel appears ___ and its hue depends on location, surface conditions of enamel, attraction to stain substances, and ages changes.
translucent
T/F. Enamel does NOT need a wet environment to maintain its integrity.
False. Enamel DOES need a wet environment to maintain its integrity.
Define attrition.
Normal, slow wearing away of tooth substances under the stress of mastication.
Are abrasion and erosion normal or not normal?
not normal
___ are pathways for diffusion of small molecules, such as water, and ___ effects on pore walls lead to carious lesions.
Microporosity; electrochemical
In ___, mineral is returned to the molecular structure of enamel by way of the ___. When this is exceeded by demineralization, ___ occurs.
remineralization; saliva; caviation
What is the inorganic substance that makes up 96% by weight of enamel?
hydroxyapatite crystals. compared to the other 3 mineralized tissues they are larger and consist of more impurities (fluoride, carbonate).
What is the principal mineral component?
calcium hydroxyapatite
How much (by weight) does the organic substance make up of enamel?
1%
What is the main protein found in enamel?
amelogenin
How are the organic enamel proteins arranged?
in a lace-like pattern throughout the volume of enamel and closely associated with the surface of the crystals
T/F. Enamel contains collagen fibers.
False, enamel does not contain collagen fibers.
How is water distributed throughout enamel?
by way of micropores between crystals and proteins
Most water forms a ___ ___ around each crystal.
hydration shell
Which CEJ relationship is most, next and least common?
most: cementum overlaps enamel
next: cementum meets enamel
least: cementum does not met enamel (causes pain)
Which cell has columnar epithelial cells?
ameloblasts
What is another name for the growth lines of enamel?
Lines or Strae of Retzius
Define perikymata.
Numerous small transverse ridges on the exposed surfaces of enamel.
Explain the relationship between Lines of Retzius and perikymata?
Lines of Retzius end on the enamel surface as grooves, ridges (perikymata) are created between the grooves.
What is the structural unit of enamel?
enamel rods
A rod has a diameter of _-_um and a lenghth of up to ___mm. There are several ___ crystallites packed into each rod.
5-6; 2.5; million
Hydroxyapatite crystals are most dense in the ___ or ___ of the rod and run ___ to the long axis of the rod.
center; core; parallel
T/F. Each rod is formed by ONE ameloblast.
True.
What is the name for the outer surface of the rod?
enamel sheath
In the enamel sheath, crystals are ___ dense than the core and run in different directions. The highest percentage of organic material is ___.
less; amelin
What substance is found in the sheath of the rods?
interrod substance
Interrod substance is secreted from two or more ___ and its crystals are ___ dense and run at different directions than those of the sheath.
ameloblasts; more
What direction do enamel rods run in comparison to the dentin surface?
right angles
Each enamel ___ is built up of segments separated by dark lines that give it a striated appearance, hence the name ___ ___.
rods; interrod striations
Why are enamel rods striated?
because it is secreted in a rhythmic manner
The ___ period of an ameloblast is marked by an interrod striation.
rest
T/F. Under the microscope, enamel rods have a fish scale appearnce.
True.
What are three examples of HYPOmineralized enamel structures?
- enamel lamella
- enamel tuft
- enamel spindle
Enamel lamellae, extend for varying depths from the surface of ___ and consist of longitudinally oriented defects filled with enamel ___ or organic debris from the ___ cavity.
enamel; protein; oral
What is the clinical significance of enamel lamella?
due to their access by acidophilic microorganisms (caries) and to stain substances (esthetic considerations)
Enamel ___ appear are ribbon-like structures that originate at the ___ surface and passes toward the ___. They may enter the dentin and pass into the ___.
lamella; enamel; dentin; pulp
What projects from the dentinoenamel junction for a short distance into enamel and contain greater concentrations of enamel protein (tuftelin)?
enamel tuft
What is the clinical significance of enamel tuft?
it contributes to the spread of caries at the DEJ
___ extend from the dentin across the ___ into the enamel for a short distance.
Spindles; DEJ
What is the clinical significance of enamel spindles?
they contribute to the spread of caries along the DEJ
Before the secretion of dentin and enamel begins, some cell processes of ___ extend between ___, and when enamel formation begins, the processes become embedded within the newly secreted enamel, resulting in the formation of the ___ ___.
odontoblasts; ameloblasts; enamel spindle
Match the following:
A. Lamella
B. Tuft
C. Spindle
I. originates at the DEJ and passes into enamel
II. originates at enamel surface and passes inward
III. originates in dentin and passes DEJ into enamel
A - II
B- I
C - III
What are alternating dark and light bands (layers) of varying width that originate at the DEJ border and pass outward ending at some distance from the outer enamel surface?
Hunter-Schreager bands
What causes Hunter - Schreager bands?
different directions of enamel rods in adjacent layers
What 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 is clinically significant when performing operative dentistry?
Hunter-Schreager bands
Where does differentiation of the inner epithelial cells of the enamel organ into ameloblasts and the peripheral cells of the dental papilla into odontoblast begin?
in the coronal most site of the future dentinoenamel junction
Ameloblast form partially mineralized or ___ enamel and move outward. ___ for predentin and move inward toward the center of the ___.
immature; Odontoblasts; pulp
What is an enamel pearl?
an ectopic enamel formation
Caries is formed from ___ enamel.
unsupported
Tetracycline staining and mulberry molars (cogenital syphilis) cause damage during what process?
odontogenesis
What does dens in dente mean?
tooth within a tooth
