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Oral Biology - Quiz 2 > Enamel II > Flashcards

Enamel II Flashcards

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1
Q

Rods and interrod enamel geometry are linked to the geometry of what?

A

Individual ameloblasts

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2
Q

Rods are __________ from the inner enamel to the outer.

A

Continuous

Innermost and outermost - NO RODS

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3
Q

The ______ end of tomes process directly forms ____ enamel rod (and surrounding interrod enamel.

A

Distal

1

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4
Q

Interrod enamel formed first, makes a what into which the enamel rod is synthesized?

A

Pit

*1 ameloblast = 1 rod, w/ correspondence from inner to outer enamel

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5
Q

Most tooth structure is _______, and how does it form?

A

Dentin

Forms inwards toward the pulp

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6
Q

Enamel is formed ________, but as a cap. The dentin forms _______, making up most of the tooth body.

A

Outwards

Inwards

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7
Q

T/F - Enamel formation is NOT simultaneous. It goes APICALLY.

A

TRUE

*Thus as the crown grows, there are new ameloblasts coming into play cervically

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8
Q

What are the 3 enamel proteins in the enamel deposition?

A

Amelogenins

Ameloblastin

Enamelin

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9
Q

What 2 enamel proteins is key in organic component degradation?

A

Enamelysin**

Enamel matrix serine protease

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10
Q

What enamel proteins are used in basal lamina during maturation?

A

Form the thing that the cells stick to

  • Amelotin
  • Odontogenic ameloblast associated protein
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11
Q

Tell me about amelogenins.

A

MAIN PROTEIN FAMILY IN DEVELOPING ENAMEL (80-90%)

  • Only expressed while enamel is being produced (stops during maturation).
  • Restricts lateral HA crystal growth, preventing crystal fusion

LOSS OF FUNCTION = NO ENAMEL RODS

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12
Q

Tell me about ameloblastin.

A

Around 10% of the enamel organic content

Expressed all the way thru to maturation

Ameloblast adhesion to developing enamel

LOSS OF FUNCTION = AMELOBLASTS FALL OFF, NO ENAMEL

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13
Q

Tell me about enamelin.

A

Least abundant enamel protein 5%

Only present at the leading edge of enamel deposition

LOSS OF FUNCTION = NO ENAMEL

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14
Q

What is enamelysin?

A

MMP - This is MMP 20

Found during enamel deposition

Chops up ameloblastin and enamelin

LOSS OF FUNCTION = THIN, IMMATURE ENAMEL

This is critical for removal of orgo component to allow increased mineralization

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15
Q

Tell me about enamel matrix serine protease.

A

Secreted during moldulation event of enamel maturation

Degrades amelogenins

Loss of function = Immature enamel

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16
Q

Basal lamina doesn’t seem to contain much if any _______.

A

Collagen IV

It has other proteins

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17
Q

Why etch?

A

Fissure sealants

Bonding restorative materials to enamel

Cementing orthodontic materials to enamel

18
Q

What does etching do?

A

Provides better bonding surface, as etching increases the porosity of the surface

Also removes any crap clinging to enamel surface

This is done be dissolving enamel crystals

19
Q

More carbonated apatite is found where?

A

In the crystal core

More vulnerable - more prevalent in inner enamel

20
Q

In etching, tell me about dissolving.

A

Inside out

Due to the carbonated apatite in crystal core

The ends first to dissolve, then along the core

21
Q

What does fluoride do?

A

Stabilizes the HA lattice by replacing the OH group

Strengthens it

Also, FA (fluroapatite) forms more quickly than HA

22
Q

Three patterns of etching.

A

I - Most common
—Removal of rods

II - Reverse of Type I, interrod enamel removed

III - Least frequent
—Irregular and indiscriminate pattern

23
Q

What is attrition?

A

Wear

Enamel cannot be replaced

May expose dentin (bad)

Topographical features pits and fissures may be eliminated

24
Q

Abrasion?

A

Removal of enamel by force

25
Q

A fraction?

A

Notch-like cervical lesions

-Caused by cyclic loading of teeth which places stress on the interrod-rod interface, causing rods to separate

26
Q

Erosion?

A

Removal of enamel by break down of crystals (via acids)

27
Q

What are some changes in enamel due to age?

A

COLOR

  • Darkness increases with age
  • Thinning of enamel
  • Extrinsic staining

NATURE OF SURFACE LAYER

  • Changes due to ionic exchange from oral environment
  • Fluoride ion most prevalent

WATER CONTENT DECREASES
-Crystals enlarge and decrease pore size

BRITTLENESS INCREASES
-Water is excluded and crystals increase in size

PERMEABILITY DECREASES
Increased crystal size and the continued exclusion of water (Less space b/t individual crystals)

28
Q

T/F - Changes in enamel over time contribute to an overall decreased incidence of caries.

A

TRUE

Higher F- content more mature enamel

29
Q

What are three structural feature of enamel?

A

Periodic
-Connected to temporal events

Optical
-Light reflection of structural features

Histological
-Results of cells doing different things

30
Q

PERIODIC FEATURE 1

Tell me what Striae of Retzius is.

A

Appear as longitudinal lines or stripes on ground sections (Thin strip of tooth, not demineralized) running from DEJ to enamel surface

May indicate a weekly rhythm in enamel deposition

May delineate different cohorts of cells as they become active at the same time in a cervical way

INCREASED ORGO CONTENT

NEONATAL LINE
-Darker line that is most accented

31
Q

What is the most accentuated stria of Retzius?

A

Neonatal line

Reflects physiologic changes occurring during birth

Found in all primary teeth, sometimes cusps of first permanent molars

32
Q

What is perikymata?

A

Surface manifestions of Striae of Retzius

Shallow furrows where stria intersect surface

33
Q

PERIODIC FEATURE 2

Cross striations. Tell me about them.

A

Visible bands or lines in ground sections

Run at a right angel to the rod direction (More or less the DEJ)

Close together, 4 micrometers/day

May indicate cyclical variations in rods

34
Q

OPTICAL FEATURE 1

Bands of Hunter-Schreger. Tell me about them

A

Visible bands in ground sections

Optical phenomenon due to differential light scattering when adj groups of rods alternate direction

Appear as alternating light/dark bands

Represent areas of enamel rods cut in cross-section dispersed b/t areas of rods cut longitudinally

35
Q

OPTICAL FEATURE 2

Gnarled Enamel. Tell me.

A

Visible in ground sections

Mostly seen around DEJ under the cusps/Invisalign area short distance into enamel

Complex twisting of rods as they proceed vertically away from the DEJ

36
Q

HISTOLOGICAL FEATURE 1

Enamel Tufts. Tell me.

A

Tufts of grass seen in ground sections - Look like cracks

Project form 1/3 to 1/2 into enamel. DO NOT REACH THE SURFACE

Contain more enamel proteins and are hypocalcified

Structurally, convey on enamel a bit of a give, helping to prevent fractures

37
Q

HISTOLOGICAL FEATURE 2

Enamel lamellae. Tell me

A

Appear as cracks in ground sections which traverse the whole length of the enamel

Contain orgo material proteins

Developmental - Areas where enamel proteins not completely removed or trapped bits of the enamel organ

May function to give enamel more structural support to resist fracture

38
Q

HISTOLOGICAL FEATURE 3

Enamel spindles. Tell me.

A

Result from odontoblastic processes that transverse the DEJ and penetrate the enamel

Proceed only a very short distance into enamel

Often appear at Invisalign and cuspal tips

NOT ENAMEL, ITS DENTIN

39
Q

What is genetic dysplasia?

A

Developmental problems with tooth development/enamel formation

Ameloblasts very susceptible to physiological changes (birth, high fever) which result in disruption in ameloblast function for a time

40
Q

What does tetracycline do?

A

It’s incorporated into all mineralizing tissues (enamel, dentin, cementum, bone)

Brown, yellow, or gray band of pigmentation

Severity proportional to dose and duration

Tooth form is normal - Basically only cosmetic

41
Q

Too much fluoride?

A

Excess fluoride interferes with amelogenesis

Results in fluorosis or motile enamel results

Hypermineralized enamel

Chalk white/brown in color

Can result in pits on teeth

Tooth form normal

Oral Biology - Quiz 2 (3 decks)

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