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41 Cards in this Set

  • Front
  • Back
What is the Ameloblast Life Cycle
Morphogenic

Organizing

Formative

Maturative

Protective

Desmolytic
Reversal of Polarity
Occurs during Organizing stage of Ameloblastic life

Basally located organelles move into apical position

Central nucleus moves into basal position
BMP
Released by mature ameloblasts

Stimulates dental papilla mesenchymal cell's MSX-1 gene

Induces mesenchymal cells to become odontoblasts
What is the first tissue that is produced during tooth formation?
Dentin
Dentinogingival Membrane
1st layer of enamel that gets laid down
Difference b/t enamel & dentin formation
odontoblasts have processes that get trapped in deposited dentin

ameloblast processes eventually break off from the cell

Also, once enamel is done getting deposited, you wont get any more laid down
Amelogenin
Enamel Proteins

rich in Proline

Two types - TRAP (tyrosine rich) and LRAP (leucine rich)

1st protein that gets laid down in the organic matrix

thixotropic properties
What is the 1st protein that gets laid down in the organic matrix?
Amelogenin
thixotropic properties
Refers to Amelogenin

flows when HAP crystals get deposited and squeezes out the Amelogenin
How do you get 96% HAP and virtually no proteins?
deposition of HAP crystals squeezes the amelogenin out of the way
Enamelin
Enamel Proteins

formed from a mixture of Amelogenin breakdown products + enzymes + serum albumin

Enamel mineralization occurs right after matrix is laid down
Primary Mineralization
accounts for the first 25-30% of the HAP crystal formation
Secondary Mineralization
rest of the mineralization that takes place, making the original HAP crystals larger

More specifically refers to what part of the enamel is getting mineralized
Hypoplasia
defects in organic matrix formation

causes mis-shaped, small teeth

Can be caused by genetic factors, systemic illness, or local trauma
Hypomineralization
defects in the mineralization process

causes soft, unsupported teeth

Can be caused by genetic factors, systemic illness, or local trauma
AMEL gene
dominant on the X chromosome in females and Y chromosome in males

Used to determine the sex of dead victims using teeth
Enamel makeup
96% inorganic + 2% organic + 2% water
Purpose of enamel
to protect the dentin underneath
Enamel Rods
basic functional unit of enamel

shape is polygonal / hexagonal in cross-section

extend from the DEJ towards the free surface

horizontal towards the cervical, more vertical towards the coronal & apical
What is the basic functional unit of enamel
Enamel rods
Gnarled Enamel
enamel rods curl, bend, twist

Increases adhesion of layer

Occurs mostly in areas like enamel tufts and near DEJ of cusps
Keyhole Hypothesis
1 ameloblast contributes to the head

3 amelboblasts contribute to the tail

each ameloblast will contribute to 4 different enamel rods
How many enamel rods do each ameloblast contribute to?
4
Ten Cate’s interpretation of Enamel Rod Structure
The head is the entire rod

The tail part is the inter-rod substance

1 ameloblast contributes to a whole entire rod

3 ameloblasts contribute to the inter-rod substance
How are HAP crystals arranged in the head region of enamel rods?
deposited parallel to e/o
How are the HAP crystals arranged in the tail region of the enamel rods?
deposited at an angle
Hunter Schreger Bands
Hypomineralized Structures

Dark & Light Bands

only be seen w/ reflective light

minimize the risk of cleavage when occlusal forces are applied

also shock absorbers
Lines of Retzius
Hypomineralized Structures

dark lines

disturbance in the growth pattern

the wider the band, the greater the disturbance

most numerous in the cervical neck of the crown
Perikymata
wherever Lines Retzius touch the tooth’s free surface

creates transverse grooves on the tooth surface

most prominent & numerous in the cervical neck
Neonatal Lines
marks the baby’s transition from pre-natal to post-natal

Due to drastic change in the environment & nutrition

It is seen as a thickened Line of Retzius
Daily Incremental Lines
represent shorter periods of growth disturbance
Structureless enamel
No rods

Seen near free surface of tooth as well as near DEJ

Occurs at beginning and end of enamel ofrmation

Found in 70% of permanent teeth, 30% of primary
Lamellae
starts at the free surface of enamel

Extends down through enamel and may cross into dentin

caused by disturbance in growth

leaf-like or ribbon-like (branched)

Hypomineralized

susceptible to bacterial acid attack
Tufts
starts at the DEJ

extends slightly into the enamel

due to disturbances in growth

does not pose as point of vulnerability
Spindles
starts at the DEJ

rope-shaped (figure 8 in cross section)

every spindle has an odontoblastic process

Tissue cannot calcify properly around the odontoblatic process
What is the shape of the DEJ in secondary dentition?
Scalloped

Increases surface area for the enamel to attach to the dentin
What is the shape of the DEJ in primary teeth?
Straight DEJ
Why doesn't tissue in pits and grooves mineralize properly?
Ameloblasts die out in the grooves and fissures
What happens to enamel as you age
It gets thinner because it is not capable of regeneration

Therefore tooth gets narrower and shorter

Enamel also gets darker

Enamel permeability decreases as pores fill up
What happens to the tooth as you age
It gets narrower and shorter because enamel gets thinner with age
How does the tooth try to compensate for the loss of contact with the opposing teeth
The crown tries to super erupt