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Dent 6534 > Tooth Microstructure > Flashcards

Tooth Microstructure Flashcards

1
Q

How many deciduous teeth are there?

A

20

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2
Q

How many permanent teeth are there?

A

32 (Many have 28 after removal of 3rd molars)

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3
Q

Function of inscisors

A

Cut and shear food
phonetics and function
esthetics

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4
Q

Function of canines

A

Seize pierce tear and cut food

Key to occlusion (protection)

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5
Q

What teeth have the longest roots and the thickest enamel?

A

Canines

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6
Q

Function of premolars

A

Grind and tear

Fine chewing

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7
Q

Function of molars

A

crushing grinding and chewing

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8
Q

Two parts of the crown of a tooth

A

Clinical-what you can see w/ gums in place

Anatomical-where enamel ends

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9
Q

Characteristics of enamel

A
  • Hard (Hardest tissue in body)
  • Translucent white
  • Shell structure
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10
Q

Characteristics of dentin

A
  • Yellowish

- Softer

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11
Q

4 layers of a tooth

A

Enamel
Dentin
Pulp complex
Cementum

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12
Q

Composition of enamel

A

1-2% Protein
6% water
90-92% inorganic (hydroxyapitite)

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13
Q

How is enamel organized

A
  • Rods or prisms run from DEJ to surface
  • Rods about 4-8 micrometers
  • Interlocking prisms made of head and tail region
  • Rods surrounded by organic sheath
  • Rods made of crystallites, surrounded by organic matrix
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14
Q

How does enamel develop?

A
  • Has epithelial origin

- Ameloblasts grow from DEJ and become extinct

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15
Q

Crystallites characteristics

A
  • composed of calcium phosphate (Hydroxyapitite)
  • Irregular and needle like in shape
  • 20nm by 160nm
  • surrounded by organic matrix
  • arrange in regular pattern within rod
    • long axis of body parallel to rod direc.
    • and tail angles up 65 degrees
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16
Q

How do rods travel from DEJ to surface

A

Wavy and spiraling path

Gnarled enamel at cervical and incisal/occlusal areas (harder to cleave)

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17
Q

Physical properties of enamel

A
  • Hard brittle and stiff parallel to rod

- Low tensile strength perpendicular to rod direction

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18
Q

What are enamel fracture lines called

A

Craze lines if dentin below is still intact

19
Q

Enamel is iso or aniso-tropic?

A

anisotropic. Looks different depending on perspective

20
Q

Best way to prep enamel

A

90 degrees w/ edge of tooth so that enamel stays supported by dentin

21
Q

Dentin composition

A

50% vol HA
25% vol collagen
25% water

22
Q

Pattern of dentin

A

striated like enamel

23
Q

Dentin development

A
  • Mesenchymal origin

- Odontoblasts grow from DEJ and remain alive

24
Q

Dentinal tubules

A
  • more mineralized than other dentin matrix
  • extend from pulp chamber to DEJ
  • related to cells that line pulpal wall (odontoblast)
25
Q

Why is the dentin just after the DEJ so sensitive

A

Dentinal tubules branch out near DEJ so its more likely to hit one

26
Q

What is peritubular dentin

A

Dentin that lines dentinal tubules

27
Q

What is intertubular dentin

A

Dentin between dentinal tubules

28
Q

What are odontoblastic processes (Tomes Fibers)

A

Deep portion of dentinal tubules before odontoblasts

29
Q

What is predentin

A

New dentin that has not mineralized yet located between odontoblasts and dentin.
Found on pulpal wall

30
Q

Function of dentinal tubules

A

Allow fluid movement and ion transport

  • remineralization
  • apposition of peritubular dentin
  • pain perception
31
Q

Superficial vs deep dentinal tubules

A

Fewer and smaller tubules in superficial section

32
Q

Dentin organization

A

Not uniformly mineralized

33
Q

Peritubular dentin vs intertubular dentin

A

Peritubular dentin is more mineralized

34
Q

Dentin structure

A
  • Principal organic component is collagen=tough
  • HA crystals w/in collagen
    • Crystal smaller than enamel
35
Q

Properties of dentin

A
  • 20% as tough as enamel
  • Higher tensile strength but lower stiffness
  • isotropic (same from all views)
  • Dentin stops propagation of cracks in enamel (holds it together)
36
Q

Dentin types

A
  • Primary dentin- forms up to 3 yrs after tooth eruption
  • Secondary-w/o obvious stimulus dentin direction changes and deposition slows
  • Reparative (tertiary)
  • Sclerotic (defense)
37
Q

How does dentin differ from enamel?

A

1) Less mineral content
2) Tubules run throughout so more fluid and ion transport
3) Ability to repair/regenerate

38
Q

Radiograph appearance

A

Enamel is whiter and more radiopaque due to mineralization

39
Q

What is cementum

A

Light yellow (slightly lighter than dentin), hard avascular structure that attaches bone to tooth

40
Q

Cementum composition

A

Similar to dentin but 5-10% less mineral content

  • 45-50% HA by weight
  • 50-55% organic matter (collagen protein polysacc and water)
  • Highest fluoride content
41
Q

Why does cementum have so much fluoride?

A

Soft and porous

42
Q

Cementum development

A

Formed continually acellularly and cellularly from cementoblasts

43
Q

Cementoblast development

A

from undifferentiated mesenchymal cells in connective tissue of dental follicle

44
Q

Cementum organization

A

CDJ: cementodentinal junc
CEJ: Cementoenamel junc aka cervical line

Dent 6534 (1 decks)

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