All Ceramic Crown Materials

Question 1

All ceramic incisal reduction:

Answer 1

1.5-2.0 mm

Question 2

All ceramic axial reduction:

Answer 2

1.0 mm on all surfaces

facially 1.2-1.5 mm depending on technique

Question 3

_____ degree shoulder or deep chamfer.

Answer 3

90-100

Question 4

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

Answer 4

rounded

dentin

Question 5

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

Answer 5

True

Question 6

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

Answer 6

True

Question 7

Which is stronger? ProCera or LAVA

Answer 7

LAVA is the strongest available

Question 8

What is LAVA made of?

Answer 8

dense zirconia

Question 9

What is ProCera made of?

Answer 9

dense alumina

Question 10

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

Answer 10

glass

reinforced leucite

Question 11

What are two defects associated with strength of ceramics?

Answer 11

1. Fabrication Defects

2. Surface Flaws

Question 12

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

Answer 12

stress-induced transformation

Question 13

What are the five methods for strengthening ceramics?

Answer 13

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

Question 14

Crystal reinforcement includes the addition of ______.

Answer 14

fillers

Question 15

What is crack blunting?

Answer 15

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)

Question 16

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

Answer 16

sizes and shapes

Question 17

Why does “Empress” provide such great esthetic qualities?

Answer 17

it is reinforced with LEUCITE

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

Question 18

Which material is close behind Empress when dealing with esthetics?

Answer 18

eMAX (lithium disillicate)

Question 19

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

Answer 19

alumina or zirconia

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

Question 20

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

Answer 20

sintered

Question 21

What is transformation toughening?

Answer 21

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

Question 22

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.

Answer 22

monoclinic

tetragonal

Question 23

Does volume change when sintering zirconia?

Answer 23

YES

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

Question 24

How do you overcome the large volume changes?

Answer 24

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

Question 25

As strength increases, what also increases?

Answer 25

opacity

Question 26

What are the three ways to make ACCs?

Answer 26

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

Question 27

"High Strength opaque substructure" is characteristic of which ACC technique?

Answer 27

Metal-Ceramic Like

Question 28

Describe the "minimal cutback" technique.

Answer 28

Porcelain is only in critical esthetic areas

Question 29

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

Answer 29

Monolithic

Question 30

What is another term for stress corrosion?

Answer 30

static fatigue

Question 31

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

Answer 31

reduced in a moist environment

Question 32

What is static fatigue caused by?

Answer 32

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)

Question 33

Describe the process of stress corrosion (static fatigue).

Answer 33

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)

Question 34

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

Answer 34

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

Question 35

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

Answer 35

contact | interface

Question 36

What are the four types of contact-initiated failures?

Answer 36

1. Partial Cone Cracks 2. Cone Cracks 3. Median Cracks 4. Chipping

Question 37

What are the five types of Interface-initiated failures?

Answer 37

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

Question 38

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

Answer 38

on the occlusal surface of the CERAMIC

Question 39

Where do radial cracks occur?

Answer 39

BETWEEN the ceramic and TOOTH - on the axial surface, at the finish line (newer ceramics) - on the occlusal surface (older ceramics)

Question 40

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

Answer 40

posterior

Question 41

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

Answer 41

True

Question 42

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

Answer 42

Feldspathic Porcelains (more posterior failures)

Question 43

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

Answer 43

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