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DEN 7111 Development > Exam 3 - Enamel Davenport > Flashcards

Exam 3 - Enamel Davenport Flashcards

1
Q

Hardest substance in the human body

A

Enamel

Hard as mild steel

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2
Q

Physical characteristics of enamel

A
  • elicit sparks when struck with flint
  • withstands tremendous mechanical forces
  • brittle
  • translucent (light yellow to grayish white)
  • variable thickness (max 2.5mm)
  • acellular/avascular
  • no collagen
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3
Q

True or false: enamel is considered an active chemical system

A

True - participates in a variety of chemical reactions

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4
Q

Most highly mineralized tissue

A

Enamel (96% inorganic material)

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5
Q

Enamel - inorganic material

A

Hydroxyapatite (crystalline calcium phosphate)

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6
Q

___ can strengthen hydroxyapatite

A

Fluoride (fluorapatite)

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7
Q

During maturation of enamel, some organic material is:

A

Reabsorbed

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8
Q

True or false: apatites are precipitated on a fibrillar substrate

A

False - they are not

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9
Q

Enamel is made of 4%:

A

water and organic material (1% protein)

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10
Q

Enamel is a ____ substance

A

Interprismatic

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11
Q

Enamel rod is thought to be ____ shaped

A

Cylindrical (keyhole shape discontinued)

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12
Q

Initial layer of enamel is:

A

Aprismatic

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13
Q

Rod crystals are oriented in:

A

The same direction

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14
Q

The long axis of the crystals is ____ to the long axis of the enamel rod

A

Parallel

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15
Q

Does interrod substance have a specific orientation?

A

Does not appear so, but slightly perpendicular to the long axis of the enamel rod

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16
Q

Rod sheath

A

optical/refractive phenomenon between the interrod substance and the enamel rod caused by the differences in hydroxyapatite crystal orientation

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17
Q

Crystallites are ____ in the rod than the interrod substance

A

Larger and more compact

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18
Q

Interrod substance looks like:

A

Honeycomb; crystals more haphazard

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19
Q

Successive enamel rods are off by _____ which contributes to a stacking in a structurally sound manner

A

2 or 4 degrees

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20
Q

Enamel rods are more ____ at cusps and _____ at cervix

A

Vertical; horizontal

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21
Q

Enamel rods run generally ____ to long axis of the tooth

A

Perpendicular

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22
Q

Enamel rods ____ as they run toward the surface

A

Undulate

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23
Q

Rod heads are always oriented:

A

Coronally

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24
Q

Rod structure allows:

A

Interlocking arrangement

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25
Q

Rate of enamel maturation depends on:

A

Nutrients available

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26
Q

Striae of Rezius

A
  • Incremental growth lines (dark bands in longitudinal section, concentric rings in cross section)
  • phasic episodes of mineral maturation
27
Q

Accentuated lines of Striae of Retzius represents:

A

Systemic disturbances

28
Q

Darker bands of Striae of Retzius means:

A

Less mineralized

29
Q

What is the neonatal line?

A

Accentuated Stria of Retzius reflecting marked physiologic change at birth

30
Q

How often is Striae of Retzius laid down?

A

Weekly (circaseptimanian)

31
Q

Enamel cross striations

A

Indicates daily circadian variation in secretory activity of ameloblasts

32
Q

Enamel cross striations result from:

A
  • Temporary constriction of Tomes’ process
  • corresponding increase in the secretory face forming interrod substance
33
Q

Hunter Schreger bands

A

Optical phenomenon produced strictly by the change in orientation of rod direction

34
Q

Gnarled enamel

A
  • found at cusp tips
  • rods appear twisted around each other in a complex pattern
35
Q

Enamel tufts are analagous to

A

Geologic faults

36
Q

Enamel tufts project from ___ for a ___ distance

A

DEJ; short (1/3-1/2 enamel thickness)

37
Q

Enamel tufts are hyper or hypomineralized?

A

Hypomineralized - increased concentration of enamel protein

38
Q

Enamel ____ can be microscopically confused with cracks

A

Lamellae

39
Q

What are enamel lamellae?

A

Linear, longitudinally oriented defects which are highly organic (hypomineralized enamel)

40
Q

True or false: enamel lamellae exacerbate caries development

A

False - do not

41
Q

Enamel lamellae have a different _____ than the rest of enamel

A

refractive index

42
Q

_____ are physical defects extending from surface for varying depths

A

Enamel cracks

43
Q

True or false: Enamel cracks have a developmental origin

A

False - physical defect

44
Q

What is the dentinoenamel junction?

A

Series of ridges that increases surface area and facilitates adhesion

45
Q

What are enamel spindles?

A

Newly formed odontoblast process that push between adjoining ameloblasts, become entrapped in enamel matrix when it mineralizes

46
Q

Carious lesion forms a ____ shape through the enamel and then ___ at the DEJ, then forms a _____ through the dentin

A

Conical; Spreads; Conical lesion

47
Q

What are perikymata?

A

Extensions of Striae of Retzius from the DEJ to the outer surface of enamel

48
Q

Perikymata run in what direction?

A

Circumferentially horizontal lines across the face of the crown (where Striae of Retzius ends on surface of tooth)

49
Q

Surface structure of unerupted teeth

A
  • Structureless cuticle of organic material
  • Subsurface layer of loosely packed crystals
50
Q

Surface structure of erupted teeth

A
  • cuticle and subsurface layer is lost
  • Salivary pellicle
51
Q

Age changes of enamel

A
  • Becomes worn
  • Discoloration
  • Reduced permeability
  • Modifications of surface layer
52
Q

Amelogenesis imperfecta causes:

A

Disruption to the structure and clinical appearance of tooth enamel

53
Q

Amelogenesis imperfecta - phenotypic classifications

A
  • hypoplastic
  • hypocalcified
  • hypomature
54
Q

Amelogenesis imperfecta is acquired via:

A
  • X-linked autosomal dominant
  • Autosomal recessive
55
Q

Best fix for amelogenesis imperfecta

A

Crown the teeth

56
Q

What are some environmental effects that affect enamel?

A
  • febrile diseases (bands of malformed enamel)
  • Tetracycline induced disturbances
  • fluoride concentrations over 5ppm can cause mottled enamel/toxic to secretory ameloblasts
57
Q

Tetracycline can get incorporated into:

A

Bone, dentin, enamel

58
Q

Fluoridation effects on enamel

A
  • crystals more resistant to acid demineralization
  • toxic to secretory ameloblasts in high concentrations (mottling of enamel)
  • enhances calcium phosphate/remineralization
59
Q

Acid etching

A
  • involved in use of fissure sealants, orthodontics
  • removes plaque and other debris
  • increases porosity of exposed surface
60
Q

Ionic substitutions to biological apatites may alter:

A
  • chemical properties
  • physical properties
  • chemical reactivity
  • hardness
61
Q

What ionic substitutions can occur on apatites?

A
  • substitution of calcium ions
  • substitution of phosphate ions
  • substitution of hydroxyl ions
62
Q

Enamel is a dynamic system which participates in what kind of interractions?

A
  • solute and ion transport from saliva to dentin
  • ion exchange with saliva
  • demineralization/remineralization
  • reactions with bacteria and other surface organic compounds
63
Q

____ is in equilibrium with oral fluid/saliva

A

Enamel

64
Q

Saliva is super saturated with:

A

Calcium and phosphate

DEN 7111 Development (19 decks)

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