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Oral Bio II > Enamel > Flashcards

Enamel Flashcards

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1
Q

What are the properties of enamel?

A

It is acellular, non-vital (no living cells), and non-vascular

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2
Q

What is the origin of enamel?

A

It is of ectodermal origin

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3
Q

What is meant by saying enamel is somewhat dynamic?

A

It can be demineralized and remineralized

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4
Q

What is the purpose of the proteins in enamel?

A

They organize the HA crystals

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5
Q

What is enamel composed of?

A

94% inorganic (HA), 1% organic (proteins), and 3% water

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6
Q

What major protein is not found in enamel? Which ones are found in enamel?

A

Collagen is not found in enamel but amelogenins, ameloblastins, enamelin, and tuftelin are found in enamel.

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7
Q

What differs between the rod and interrod enamel?

A

The orientation is different locking the two together so it resists shear forces

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8
Q

What separates the rod and interrod enamel?

A

A sheath where the protein component of enamel is located

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9
Q

HA is the most common type of crystal found but there is a good amount of what other type of crystal? What does this cause?

A

Carbonatoapatite (carbonated apatite). It causes a change in the shape crystal making it so that it doesn’t pack together as well. It is more common in the deeper layers because ameloblasts produce carbonate and it gets integrated into the crystals

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10
Q

What shape are the enamel crystals?

A

Hexagonal, they are 60-70nm wide and 25-30nm thick, they get bigger as they mature and kind of lose their hexagonal shape and become slightly more rounded

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11
Q

In what direction do the enamel rods run?

A

Perpendicular to the DEJ

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12
Q

How are enamel rods organized?

A

In rows, alternating the the direction in which they run.

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13
Q

How much of the rod is surrounded by the sheath?

A

about 3/4s of the rod

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14
Q

How many ameloblasts contribute to the “keyhole” interrod enamel? How many ameloblasts contribute to one rod?

A

4 and 1 respectively

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15
Q

What percent of initial enamel deposit is mineralized?

A

Only about 30%

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16
Q

What causes the initial deposition of enamel?

A

The pre dentin that is secreted by the odontoblasts

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17
Q

What are the 3 phases of ameloblast maturation?

A

Pre-secretory (from pre-ameloblasts to ameloblasts), Secretory (deposition of enamel) Maturation (reduction of organic component and increased mineralization via ion transport)

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18
Q

What does the apical end of the ameloblast form when it is in the secretory phase?

A

Tome’s processes. (Not Tome’s fibers)

19
Q

T or F: Initial enamel has rods?

A

False, it is uniform. The interrod enamel starts first forming a pit for the Tome’s processes to form in.

20
Q

Does the outermost layer of enamel have rods?

A

No because the Tome’s processes retract as they get to the end. So Tome’s processes equal enamel rods.

21
Q

What happens after enamel deposition stops?

A

Ameloblasts return to squat shape, and form a new basal lamina. OEEs and IEEs fuse to make REE. In order to harden the enamel, water and organic component must be removed.

22
Q

How much time of amelogenesis is spent in maturation?

A

About 2/3s of the time

23
Q

What are the two phases that happen during maturation?

A

Ruffled-during this phase enzymes are secreted into the enamel that break down the protein parts and promote HA crystal growth. Smooth-As the crystals get bigger, it forces the water and broken down proteins out, in order for this to occur the cells change to smooth apical ends

24
Q

What is the primary enamel cuticle?

A

The partially mineralized basal lamina

25
Q

What is the secondary enamel cuticle?

A

Remnants of the REE and oral epithelium

26
Q

Where is the enamel uniform?

A

At the innermost and outermost portions. No rods

27
Q

Which are straighter, inner 2/3s or outer 1/3 of enamel rods?

A

Outer 1/3. less crowding

28
Q

What enamel is deposited first?

A

Interrod enamel is laid down first

29
Q

T or F: Enamel formation happens simultaneously?

A

False. Enamel formation occurs apically

30
Q

What are the facts about amelogenin proteins?

A

The are the most abundant protein during enamel deposition (80-90%), restricts lateral HA crystal growth preventing fusion

31
Q

What is the function of ameloblastin?

A

It help adhere the ameloblasts to the developing enamel. If it is damaged ameloblasts fall off. Make up 10% of proteins

32
Q

What part of the HA crystal dissolves first from etching?

A

The core, it then moves outward dissolving from the inside out

33
Q

What are the three types of enamel etching patterns?

A

Type I- Rods removed Type II- Interrod removed Type III- Irregular

34
Q

Name the four types of enamel wear

A

Attrition, abrasion, abfraction and erosion

35
Q

What are the striae of retzius?

A

Like tree rings they are lines in the enamel that mark the appositional growth pattern or cohorts of ameloblasts that are active at the same time

36
Q

What is the neonate line?

A

It is a line in the striae of retzius that is darker than the rest and marks a point of physiological disturbance

37
Q

What are perikymata?

A

The surface presentation of the striae of retzius

38
Q

What are cross striations?

A

Light lines that run at a 90º angle to the rods, mark the amount of deposition per day about 4µm/day

39
Q

What are bands of Hunter-Schreger?

A

They are an optical phenomenon that occurs in the inner 2/3s of enamel caused by the crossing of enamel rods that scatter the light differently

40
Q

What is gnarled enamel?

A

A complex twisting of enamel rods as they move vertically away from the DEJ

41
Q

What are enamel tufts?

A

They look like tufts of grass in a ground section that go to about 1/2 to 2/3s of the enamel

42
Q

What are enamel lamellae?

A

Bits of organic substance that doesn’t get removed from the enamel and span the entire length of the enamel

43
Q

What are enamel spindles?

A

Parts of the odontoblastic process that enters into the enamel

Oral Bio II (8 decks)

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