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Au 15- Fixed 3 Final Exam > All Ceramic Crown Materials > Flashcards

All Ceramic Crown Materials Flashcards

1
Q

All ceramic incisal reduction:

A

1.5-2.0 mm

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2
Q

All ceramic axial reduction:

A

1.0 mm on all surfaces

facially 1.2-1.5 mm depending on technique

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3
Q

_____ degree shoulder or deep chamfer.

A

90-100

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4
Q

Internal line angles should be _____ to reduce stress on the _____.

A

rounded

dentin

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5
Q

True or False: All-ceramics have a more consistent esthetic outcome than MCCs.

A

True

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6
Q

True or False: There is a gradual increase in strength of ceramics that are used so that metal substructure is no longer needed.

A

True

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7
Q

Which is stronger? ProCera or LAVA

A

LAVA is the strongest available

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8
Q

What is LAVA made of?

A

dense zirconia

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9
Q

What is ProCera made of?

A

dense alumina

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10
Q

Porcelain is made of _______, Empress is made of _____ ________, and eMAX is made of lithium Disillicate.

A

glass

reinforced leucite

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11
Q

What are two defects associated with strength of ceramics?

A
  1. Fabrication Defects

2. Surface Flaws

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12
Q

The _________ in zirconia grains produces compressive stresses within the transformed grains and surrounding glassy matrix, as well as circumferential tensile stresses around the grains.

A

stress-induced transformation

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13
Q

What are the five methods for strengthening ceramics?

A
  1. Crystal Reinforcement
  2. Chemical Strengthening
  3. Stress-Induced Transformation
  4. Glazing
  5. Prevention of Stress Corrosion
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14
Q

Crystal reinforcement includes the addition of ______.

A

fillers

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15
Q

What is crack blunting?

A

Reinforced glass has additional crystals which cause the progression of cracks to follow a more difficult path, rather than a straight line (deflects progression). Also, it slows down the crack growth process by interfering with the path (SLOW down and CHANGE the path)

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16
Q

Crystals used for reinforcement have different ____ and _____ that result in different strengths.

A

sizes and shapes

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17
Q

Why does “Empress” provide such great esthetic qualities?

A

it is reinforced with LEUCITE

-leucite doesn’t fog the crystal or give an opaque appearance like others do

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18
Q

Which material is close behind Empress when dealing with esthetics?

A

eMAX (lithium disillicate)

19
Q

ProCera is either made of ______ or _______. Compare the two.

A

alumina or zirconia

  • alumina is less dense
  • alumina does not go through transformation toughening
  • zirconia is stronger (1120 compared to 683 MPa)
20
Q

Materials become stronger when they are ______ because the crystals are more dense.

A

sintered

21
Q

What is transformation toughening?

A

stress induces crystals to transform from one lattice state to a different lattice state which increases the volume and closes the cracks

22
Q

Pure zirconia undergoes a phase transformation from ______ (at room temp) to ______ (at 100 degrees C) and then to cubic at much higher temperatures just prior to melting.

A

monoclinic

tetragonal

23
Q

Does volume change when sintering zirconia?

A

YES

  • there is a very large volume change (9%)
  • which is why it is difficult to obtain stable sintered zirconia products
24
Q

How do you overcome the large volume changes?

A

the tetragonal polymorph is stabilized by substituting some of the zirconia ions in the lattice with larger ions (such as Y 3+) = stabilized zirconias

25
Q

As strength increases, what also increases?

A

opacity

26
Q

What are the three ways to make ACCs?

A
  1. Metal-Ceramic Like ($$$)
  2. Minimal Cutback ($$)
  3. Monolithic ($)
27
Q

“High Strength opaque substructure” is characteristic of which ACC technique?

A

Metal-Ceramic Like

28
Q

Describe the “minimal cutback” technique.

A

Porcelain is only in critical esthetic areas

29
Q

“Moderate strength, translucent ceramics” are characteristic of which ACC technique?

A

Monolithic

30
Q

What is another term for stress corrosion?

A

static fatigue

31
Q

Static Fatique/Stress Corrosion is a mechanism by which the strength of ceramics is __________.

A

reduced in a moist environment

32
Q

What is static fatigue caused by?

A

the reaction of water at the area around the crack tip which results in an increase in crack size
(strain between Si-O-Si bonds)

33
Q

Describe the process of stress corrosion (static fatigue).

A
  1. Chewing on ceramic (functional load)
  2. Underside of crown is stressed
  3. Existing cracks are strained
  4. Water enters the crack and reacts (-OH groups)
  5. Crack slowly expands over time (slow)
34
Q

How do you prevent of delay the stress corrosion process (3 ways)?

A
  1. Metal Substructure (PFM or MCC)
  2. Reduce more tooth structure (makes ceramic thicker)
  3. Use Stronger/stiffer ceramics
35
Q

Failure of Ceramic crowns is _______-initiated or ______-initiated.

A

contact

interface

36
Q

What are the four types of contact-initiated failures?

A
  1. Partial Cone Cracks
  2. Cone Cracks
  3. Median Cracks
  4. Chipping
37
Q

What are the five types of Interface-initiated failures?

A
  1. Partial Cone Cracks
  2. Cone Cracks
  3. Median Cracks
  4. Chipping
  5. Radial Cracks
38
Q

Where do partical cone, cone, and median cracks occur?

A

on the occlusal surface of the CERAMIC

39
Q

Where do radial cracks occur?

A

BETWEEN the ceramic and TOOTH

  • on the axial surface, at the finish line (newer ceramics)
  • on the occlusal surface (older ceramics)
40
Q

Early studies show that weaker ceramics had high failure rates in _______ teeth (old materials)

A

posterior

41
Q

True or False: Based on meta-analysis (34 studies), failure rates between posterior and anterior crowns are almost equivalent.

A

True

42
Q

The greatest “inequality in strength for anterior compared to posterior” is for which product?

A

Feldspathic Porcelains (more posterior failures)

43
Q

Which three ceramic products have relatively equal rates of failure between posterior and anterior crowns?

A
  1. Reinforced Silica-Based
  2. Glass-Infiltrated Ceramic
  3. Dense Sintered Zirconia

Au 15- Fixed 3 Final Exam (2 decks)

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