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Dental Development and Anatomy > Enamel (Lecture 1) > Flashcards

Enamel (Lecture 1) Flashcards

1
Q

Reconstructed early oral cavity

At about ____, the primary epithelial band forms in presumptive upper and lower jaws at future dental arch. • The band thickens by ____ proliferation perpendicular to the surface.

A

5 weeks

epithelial

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2
Q

____: the process whereby a tooth develops from a few cells in the primitive oral cavity to an erupted tooth with crown and root

A

odontogenesis

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3
Q

____: enamel formation

A

amelogenesis

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4
Q

Enamel: a unique ____ tissue that covers the crown of the tooth

A

epithelial

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5
Q

Cap stage of tooth development

The bud splits into a ____ structure due to proliferation.
• The epithelium forms the ____.
• ____ cells aggregate beneath the enamel organ, to form the ____. •
The ____ forms.

A 
cap-like
enamel organ
ectomesenchymal
dental papilla
dental follicle (sac)
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6
Q

Timing of developmental stages

Primary epithelial band:
Bud stage:
Cap:
Bell:
Crown:
A 
5 weeks, initiation
6-8, in-growth
8-12, morphogenesis
12-16, differentiation
18, mineral forms
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7
Q

The terms (bud, cap, bell, crown) refer to the ____ in the dental organ.

A

morphological changes

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8
Q

Bell Stage
• During bell stage, the undersurface of the enamel organ ____, and ____ begins.
• Epithelial cells assume different appearances in preparation for formation of the ____

A

deepens
cellular histo-differentiation
hard tissue

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9
Q

Bell Stage: Epithelial cell differentiation

4 epithelial cell types during bell stage are
• Outer dental epithelium (EDE) – \_\_\_\_ 
• Stellate reticulum (SR) – \_\_\_\_ 
• Stratum intermedium (SI) - \_\_\_\_
• Inner dental epithelium (IDE) - \_\_\_\_
A

cuboidal cells
star-shaped cells
several flattened layers
short columnar

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10
Q

During ____, inner dental epithelium folds according to tooth type

A

bell stage

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11
Q

Ameloblasts and Odontoblasts

  • Precursors (____) stop proliferation
  • Epithelial and ____ signal to each other using secreted proteins as instructions for differentiation
  • Cells elongate and change organelle components for secretory function
  • Begin to secrete ____
A

inner dental epithelial and ectomesenchymal cells
ectomesenchymal cells
extracellular matrix (ECM)

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12
Q

Late Bell/Early crown stage

During bell stage, ____ folds according to tooth type
The ____ reduces in thickness at locations of ____
Differentiation continues down the slopes of ____

A

inner dental epithelium
stellate reticulum
mineral formation
developing crown

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13
Q

After first dentin is secreted and mineralizes, ameloblasts secrete first enamel toward the ____
• Ameloblasts then retreat ____, forming ____, which creates structure in enamel
• Are in contact with ____, which contains alkaline phosphatase
• Ameloblasts & SI are considered a ____

A 
basement membrane
peripherally
tomes' process
stratum intermedium (SI)
functional unit
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14
Q

Enamel

____ tissue in the body
• Product of ____
• Extracellular matrix (secreted material) that contains ____

A

hardest
epithelial cells
no collagen

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15
Q

As ameloblasts change in morphology, their ____ change as well. Each ameloblast goes through all stages, but at different times.
• ____ ameloblasts produce most of the enamel matrix
• ____ is a short stage where secretion slows, and many ameloblasts die by apoptosis. Remaining cells shorten and excess organelles are digested

A

functions
secretory
transition

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16
Q

____: Maturative ameloblasts secrete a basal lamina on the enamel surface and attach to it by ____
• Maturative ameloblasts remove proteins from developing enamel & replace organic material with ____
• ____ ameloblasts continue to modify enamel composition.

A

maturation
hemidesmosomes
calcium and phosphate
protective

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17
Q

Maturation stage ameloblasts

Exist in ____ morphologies
• ____ ameloblasts permit
removal of peptides and water
• ____ ameloblasts transport calcium and phosphate to the enamel
• Cells cycling between stages are undergoing ____

A

two
smooth-ended
ruffle-ended
modulation

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18
Q

Reduced Dental Epithelium

  • As mineralized dentin and enamel form, the ____ compresses, and ____ is no longer visible
  • The remaining layers of the enamel organ form the ____
A

dental organ
stellate reticulum
reduced dental epithelium

19
Q

Secretory Stage:

Amelogenins (____ of ECM)
-Amelogenins are small ____ proteins with conserved amino acid sequence
-Amelogenins assemble; they regulate ____
-Amelogenins are ____ Genes on X and Y chromosomes Proteolysis produces ____;
____ produces many mRNAs that encode amelogenin proteins

A 
90%
hydrophobic
crystal growth and enamel thickness
heterogeneous
peptides
alternative splicing
20
Q

Secretory Stage: Non-amelogenins (____ of ECM)
-____ – acidic; found at ____; involved in crystal nucleation
-____ – (amelin, sheathlin)
found in rod sheath
interaction between cell and ECM
expressed in secretory, maturation, by HERS
-____ – protease that processes enamel proteins during ____

A 
10%
enamelin
DEJ
ameloblastin
MMP20 (matrix metalloproteinase 20)
secretory stage
21
Q

Stages of Amelogenesis

____ Stage
• Ameloblasts shorten and organelles rearrange • Some ameloblasts die - apoptosis

____ Stage
• ____ is secreted and degrades most remaining enamel proteins
• Protein is removed from developing enamel; calcium and phosphate are added

A

transition
maturation
KLK4 protease

22
Q

Enamel Composition

Secretion
Protein:
Mineral:
Water:

Maturation
Protein:
Mineral:
Water:

A

66%
29%
5%

4%
95%
1%

23
Q

Enamel structure: Hydroxyapatite

  • Formula is ____
  • A unit cell is the ____ repeating unit
  • Unit cells stack to form the repeating unit of the ____
  • ____ can substitute for OH-
A

Ca10(PO4)6(OH)2
smallest
lattice
fluoride

24
Q

The ____ is a space created by groups of crystals that orient at ____.
• Small amounts of protein remain in the rod sheath (e.g., ____).
• The rod sheath separates ____.

A

rod sheath
angles
sheathlin
enamel rods (prisms)

25
Q

Rod sheaths

Before ____ extends, enamel rods are not formed.
• Secretory granules containing enamel proteins are released from the ____.
• The membrane of the granule fuses with the cell membrane, and the contents are released outside the ameloblast by ____

A

Tomes’ process
ameloblast
exocytosis

26
Q

Rod sheaths

Crystals in rod and interrod enamel are similar in ____ and ____ but diverge in ____

A

structure
composition
orientation

27
Q

Striae of Retzius and lamellae

  • ____ are daily increments of enamel secretion.
  • ____ are prominent striations or developmental lines in enamel.
  • ____ end at the enamel surface in shallow furrows called ____.
  • ____ are faults in the enamel mineral, probably due to ____.
A 
cross-striations
striae of retzius
striae
perikymata
lamellae
incomplete mineralization
28
Q

Enamel Tufts

Enamel tufts extend from the ____ into enamel. They are ____ structures that contain the protein ____

A

DEJ
feather-like
tuftelin

29
Q

Enamel Spindles

Enamel spindles are formed when ends of ____ are embedded in enamel during ____

A

odontoblast processes

development

30
Q

Physical characteristics of enamel

  • ____ due to the high mineral content.
  • Also ____, but the underlying ____ provides resilient support
  • ____ and varies in thickness, from 2.5 mm at the tip of cusp to very thin at the ____
A 
very hard
brittle
dentin
translucent
cervical line
31
Q

Enamel Demineralization

•  Three acid etching patterns. 
–  Type I – \_\_\_\_.
•  Preferential removal of \_\_\_\_. 
–  Type II.
•  Reverse of type I – \_\_\_\_ removed.
–  Type III – \_\_\_\_
•  \_\_\_\_ pattern.
A 
most common
rods
interrod enamel
least frequent
irregular and indiscriminate
32
Q

Changes in enamel

  • During aging, enamel can erode as it is not ____
  • When ____ is adsorbed onto the crystals, enamel becomes more resistant to ____, which helps resist caries.
  • Excess ____ interferes with enamel development, leading to ____
A 
regenerated
fluoride
acid dissolution
fluoride
fluorosis
33
Q 
•  Fluoride-induced defects.
–  Fluoride ions are incorporated into the
\_\_\_\_, preventing caries.
–  Excess fluoride interferes with \_\_\_\_. –  \_\_\_\_ results.
–  \_\_\_\_ enamel.
–  Chalk white or brown in color.
–  Very resistant to caries.
–  Tooth form is \_\_\_\_.
A 
hydroxylapatite crystals
amelogenesis
fluorosis or mottled enamel
hypomineralized
normal
34
Q

Summary

  1. Ameloblasts develop from ____ and require communication with ____ (future odontoblasts) in order to differentiate.
  2. Ameloblasts change in shape and function during enamel development.
  3. The principle stages of enamel development are ____, ____ and ____.
A 
inner dental epithelium
ectomesenchyme cells
secretion
transition
maturation
35
Q

Summary

  1. Ameloblasts secrete a unique extracellular matrix containing enamel proteins (____, enamelin, ameloblastin and proteases (____ and ____).
  2. Ameloblasts secrete ____ and subsequently process and remove enamel proteins as the enamel ____.
  3. Ameloblasts also direct movement of ____ and ____ into developing enamel.
  4. Ameloblasts are lost before the tooth ____ into the oral cavity.
A 
amelogenin
MMP20
KLK4
first
hardens
calcium
phosphate
erupts
36
Q

Summary

  1. Enamel is also influenced by environmental ____ and ____ during tooth development.
  2. Enamel is the ____ tissue in the body because of the high mineral amount and the ____ of mineral crystals.
  3. Genetic mutations in genes encoding enamel proteins or proteases lead to the inherited enamel defect ____.
A 
fluoride
fever
hardest
orderly orientation
amelogenesis imperfecta
37
Q

Age Changes in Enamel

• Attrition.
– Enamel is ____.
– Attrition of enamel may expose dentin. – Pits and fissures may be eliminated.

• Color.
– Darkness ____ w/age.
– Thinning of enamel.
– Extrinsic staining.

A

non-vital

increases

38
Q

Age Changes in Enamel

•  Permeability.
–  \_\_\_\_ with age.
–  \_\_\_\_ pore size between crystals; crystals \_\_\_\_ in size;
•  Water content.
–  \_\_\_\_ with age.
–  \_\_\_\_ pore size forces water out.
A 
decreases
decrease
increase
decrease
decreasing
39
Q

Age Changes in Enamel

•  Nature of surface layer.
–  Changes due to ionic exchange with oral
environment.
–  Fluoride ion most prevalent.
•  Topical application.
•  Brittleness - \_\_\_\_ w/age.
A

increases

40
Q 
Age Changes in Enamel
•  Decreased \_\_\_\_ of caries.
– \_\_\_\_ Fluoride ion content.
– Loss of \_\_\_\_ susceptible to caries.
– Change in diet – less \_\_\_\_ consumed by adults.
A

incidence
increased
surface areas
refined carbohydrates

41
Q

Disturbances in Enamel Formation

  • ____ – amelogenesis imperfecta (AI).
  • Ameloblasts are very susceptible to changes in their environment.
  • Minor physiologic changes → structural changes visible only ____.
  • ____ insults → damage or death of ameloblasts with easily visible defects.
A

genetic dysplasias
histologically
severe

42
Q

Disturbances in Enamel Formation
• Febrile disease-induced defects.
– ____ causes disturbance in enamel
formation.
– Enamel formed during this time period is ____.
– Enamel formation returns to normal with ____.

A

fever
malformed
remission of fever

43
Q 
Disturbances in Enamel Formation
•  Tetracycline-induced defects.
–  Tetracycline antibiotics are incorporated into all \_\_\_\_ (enamel, dentin, cementum and bone).
–  \_\_\_\_ band of pigmentation.
–  Severity \_\_\_\_ to dose and duration.
–  Tooth form is \_\_\_\_.
A

mineralizing tissues
brown, yellow, or gray
proportional
normal

44
Q

emdogain = ____

A

shit

Dental Development and Anatomy (13 decks)

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