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Oral Biology II > Enamel > Flashcards

Enamel Flashcards

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1
Q

Underlying dentin support is critical for enamel functions because of what property of enamel?

A

Brittleness

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2
Q

What are the 3 main components of enamel?

A
  • Organic (1-2% enamel proteins, NOT collagen)
  • Water (2-3%)
  • Inorganic hydroxyapatite
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3
Q

Enamel crystals pack closely together to form what two structures?

A

-Enamel rods and interrod enamel

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4
Q

What are the three main variations of hydroxyapatite?

A
  • Carbonatoapetite (more vulnerable to acid)
  • Magnesium incorporated (more vulnerable to acid)
  • Flourapetite (less vulnerable to acid)
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5
Q

Where are carbonate and magnesium incorporated enamel more prevalent?

A

Inner enamel

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6
Q

Each enamel crystal is roughly 60-70 nm wide, 25-30 nm thick, very long and what general shape?

A

Hexagonal

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7
Q

In what orientation would you expect to find enamel rods in reference to the DEJ?

A

Perpendicular, or close to it, possibly curving and intertwining as they approach the surface

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8
Q

The protein rich areas surrounding enamel rods are called?

A

Rod Sheath

*runs 3/4 of the way around the rod, connecting rod and interrod enamel crystals

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9
Q

What are two examples of enamel rod sheath proteins?

A

1-Ameloblastins

2-Amelogenins

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10
Q

Rather than the keyhole analogy, what is a more accurate way to describe the rod-interrod relationship?

A

Columns embedded in interrod enamel

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11
Q

Ameloblasts contribute to what structures in the enamel?

A

An enamel rod and the surrounding interrod enamel

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12
Q

As enamel matures organic component is ________ and mineralization ________

A

decreases, increases

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13
Q

What are the 3 general phases of ameloblast maturation?

A

1-Pre-secretory
2-Secretory
3-Maturation (reduction of organic matrix, increase mineralization)

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14
Q

The youngest ameloblasts are found where on the tooth?

A

Cervical portion

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15
Q

What binds ameloblasts together to keep them moving in sync?

A

Junctional complexes (terminal bars)

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16
Q

When is enamel in an amorphous state rather than in rods?

A 
initial enamel (tomes process is not yet formed)
outermost enamel (tomes process have retracted)
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17
Q

What are tomes processes responsible for?

A

forming the enamel rod structure

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18
Q

Disruption of the proteins in the unique basal lamina at the external surface of enamel can result in what?

A

enamel Hypoplasia

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19
Q

Infiltration and incorporation of calcium ions into crystals occurs during which mature ameloblast conformation?

A

Ruffled cell

*Also secretes proteolytic enzymes

20
Q

The diffusion out of protein fragments from the enamel, occurs during which mature ameloblast conformation?

A

Smooth cell

21
Q

The last secretory product of ameloblasts is called what?

A

Primary enamel cuticle

22
Q

The remains of the reduced enamel epithelium merged with oral epithelium is called what?

A

Secondary enamel cuticle

*is removed due to mechanical forces

23
Q

The inner _______ of enamel are somewhat interwoven while the outer _______ is much straighter

A

2/3, 1/3

24
Q

What are three examples of enamel deposition proteins?

A

1-Amelogenin
2-Ameloblastin
3-Enamelin

25
Q

Only expressed while enamel is being produced, which protein restricts lateral HA crystal growth and is the main protein family (80-90%) in developing enamel?

A

Amelogenin

*no rods without it

26
Q

Expressed all the way through maturation, which protein adheres ameloblasts to developing enamel and make up about 10% of the organic material in enamel?

A

Ameloblastin

*no enamel without it

27
Q

Only present on the leading edge of enamel deposition, which protein possibly promotes crystal elongation and is least abundant (5%)?

A

Enamelin

*no enamel without it

28
Q

Found during enamel deposition, which protein is an MMP and chops up ameloblastin and enamelin, and is critical for removal of organic component of enamel?

A

Enamelysin

29
Q

Secreted during modulation events of enamel maturation, which protein degrades amelogenins?

A

Enamel matrix serine protease

30
Q

Instead of using collagen, the basal lamina on the enamel is made up of what?

A

Other proteins such as ODAM and Amelotin

31
Q

Etching tends to be more effective by dissolving how?

A

Inside out, along the core. Carbonated apatite in core are most vulnerable

32
Q

What are the 3 types of enamel etching?

A

Type I- Preferential removal of rods (most common)
Type II-Interrod enamel removed
Type III-Irregular and indiscriminate pattern (least common)

33
Q

What are three kinds of enamel wear?

A

1-Abrasion (ie. aggressive brushing)
2-Abfraction (notch like cervical lesion caused by cyclical loading)
3-Erosion (Break down of crystals, acid attack)

34
Q

How does enamel change with age?

A 
1-Color (stain, thin enamel)
2-Surface layer chemistry (fluoride)
3-Decrease water content
4-Increased brittleness
5-Decreased permeability
35
Q

What are the three categories of structural features of enamel?

A

1-Periodic features (Striae of Retzius, cross striations)
2-Optical features (Hunter-Schreger bands, gnarled enamel)
3-Histological features (tufts, lamellae, spindles)

36
Q

Longitudinal lines running from DEJ to enamel surface likely due to cohorts of ameloblasts activating at the same time are called what?

A

Striae of Retzius

*Follow appositional growth pattern, may indicate weekly rhythm in enamel deposition

37
Q

What is an example of an accentuated striae indicative of physiological disturbance?

A

Neonatal line (birth line)

38
Q

Visible on the enamel surface, what optical feature are manifestations of Striae of Retzius?

A

Perikymata

39
Q

Running at a right angle to the rod direction, what feature is indicative of daily deposition of enamel?

A

Cross Striations

*roughly 4 um/day which is how far apart these striations are

40
Q

An optical phenomenon caused by light scattering off alternating rods, appearing as alternating light/dark bands are called what?

A

Bands of Hunter-Schreger

*Extend 2/3 distance from DEJ to surface. Outer 1/3 is straighter

41
Q

Mostly seen around the DEJ under cusps, what feature forms complex twisting rods?

A

Gnarled enamel

42
Q

Projecting about 1/3-1/2 into enamel, what feature contains more enamel proteins and thus are hypo calcified and look like cracks or grass?

A

Enamel tufts

*Possibly due to initial crowding of ameloblasts, gives the enamel a bit of “give”, helping to prevent fracture

43
Q

Appearing as cracks transversing the length of enamel, what feature is an area where enamel proteins were not completely removed?

A

Enamel Lamellae

44
Q

Resulting from odontoblastic processes that penetrate the enamel, what feature often appear at incisal and cuspal tips a very short distance into enamel?

A

Enamel Spindles

*not really enamel

45
Q

What are 4 disturbances to enamel formation?

A

1-Genetic dysplasia
2-Disruptions in ameloblast function or life
3-Tetracycline (stains brown)
4-Fluoride (chalky white

Oral Biology II (13 decks)

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