All-Ceramics II

Question 1

The actual strength of a ceramic is always what

Answer 1

lower than its theoretical strength

Question 2

What is the differences of the theoretical strength and the actual strength of ceramics

Answer 2

theoretical strength = 7000MPa

actual strength = 35-50MPa

Question 3

What two things contribute to strengthening mechanisms of ceramics

Answer 3

fabrication defects

surface flaws

Question 4

Who proposed that flaws act as a stress concentrator (magnifiers)

Answer 4

Griffiths

Question 5

What does stress concentration apply

Answer 5

low locally applies stresses can result in very high effecting local stresses

Question 6

What are two fabrication defects of ceramics

Answer 6

sintered powders introduce voids

casting and pressing result in potentially less flaws

Question 7

What are two surface flaws of ceramics

Answer 7

grinding can introduce flaws (this is why polishing or re-glazing is critical)
usually failure occurs from the largest flaws

Question 8

What are two aspects of chemical strengthening of ceramics

Answer 8

puts surface of ceramic in compression (pre-stress)

not commonly used in dentistry

Question 9

What are two aspects in glazing of ceramics

Answer 9

self-glazing; tends to heal flaws

surface glazing can be designed to cool so they are under surface compression to improve strength

Question 10

What are two characteristics of preventing stress corrosion of ceramics

Answer 10

ceramics are weaker when fracture occurs in water; water reacts with ceramics
ceramics fused to metal foil (captek) can reduce this

Question 11

This is used to strength the ceramics

Answer 11

crystalline reinforcement

Question 12

What is crystalline reinforcement

Answer 12

introduce increased crystal content in the glassy matrix to deflect cracks

Question 13

What are two examples of glass ceramics crystalline reinforcement

Answer 13

glass ceramics; both silica based
leucite-reinforces (Empress)
lithium disillicate (eMax)

Question 14

What is the strength of glass ceramics

Answer 14

moderate

Question 15

What is the translucency of glass ceramics

Answer 15

good translucency

Question 16

In which type of restorations can glass ceramics be used

Answer 16

full thickness restorations

Question 17

In which three ways can glass ceramics be formed

Answer 17

pressing
machining
sintered powders

Question 18

How is the shrinkage/fit of glass ceramics

Answer 18

no shrinkage/good fit

Question 19

What is the strength of crystalline reinforced glass infiltrated alumina (InCeram)

Answer 19

high strength

Question 20

What is the translucency of crystalline reinforced glass infiltrated alumina (InCeram)

Answer 20

poor

Question 21

What is the shrinkage of crystalline reinforced glass infiltrated alumina (InCeram)

Answer 21

no shrinkage

Question 22

What is crystalline reinforced glass infiltrated alumina (InCeram) used for

Answer 22

a core

Question 23

How can you fabricate crystalline reinforced glass infiltrated alumina (InCeram)

Answer 23

it can be fabricated without special equipment

Question 24

What is the strength of crystalline reinforced dense sintered alumina

Answer 24

high

Question 25

What is the translucency of crystalline reinforced dense sintered alumina

Answer 25

low

Question 26

What is crystalline reinforced dense sintered alumina used as

Answer 26

a core only

Question 27

How can you fabricate crystalline reinforced dense sintered alumina

Answer 27

special equipment machine (CAD) | high temp ovens

Question 28

What is the strength of stress-induced transformation dense sintered zirconia

Answer 28

high

Question 29

What is the translucency of stress-induced transformation dense sintered zirconia

Answer 29

variable

Question 30

What is stress-induced transformation dense sintered zirconia used as

Answer 30

a core or full thickness restoration

Question 31

How can you fabricate stress-induced transformation dense sintered zirconia

Answer 31

special equipment machining (CAD) | high temp ovens

Question 32

What steps happen when stress-induced transformation dense sintered zirconia undergoes stress

Answer 32

it leads to cracks the lack of crystal constraint leads to crystals expanding (transformation) resulting in reduced stress at crack tip

Question 33

What are the four all ceramic systems available at OSU

Answer 33

Leucite reinforced glass-ceramic lithium di-silicate glass-ceramic full contour zirconia porcelain fused to zirconia

Question 34

What are two characterics of forming empress and eMax press

Answer 34

lost wax technique | hot-pressed

Question 35

In which two ways an Empress and eMax be used

Answer 35

full contour with surface stain and glaze | minimal cutback with porcelain veneer

Question 36

This type of fabrication technique is less labor intensive (less expensive), excellent outcomes, and has the full contour strength of material

Answer 36

surface staining

Question 37

This fabrication technique is more labor intensive and expensive, excellent outcomes, full counter strength of material in high stress areas like the lingual or occlusal surfaces

Answer 37

minimal cutback with layered porcelain

Question 38

This fabrication technique is the most labor intensive and expensive, has excellent outcomes, and the strength of material is reduced because thickness is reduced

Answer 38

full cutback with layered porcelain

Question 39

How is zirconia supplies

Answer 39

isostatically pressed powders, stronger than chalk in this state but easy to mill

Question 40

How much shrinkage does zirconia undergo

Answer 40

20%

Question 41

What is the strength of zirconia

Answer 41

>1000MPa

Question 42

What is the crystalline structure of zirconia at room temperature

Answer 42

largest; monolinic

Question 43

What is the crystalline structure of zirconia at 1170℃

Answer 43

intermediate; tetragonal

Question 44

What is the crystalline structure of zirconia at 2370℃

Answer 44

smallest; cubic

Question 45

Adding small amounts of this will cause the powders to stabilize in the tetragonal phase

Answer 45

yttrium (3%)

Question 46

What is transformation toughening

Answer 46

crack causes local crystals to be unconstrained in some area lack of crystal constraint allows phase transformation phase transformation results in increase in crystal size increase in crystal size closes crack

Question 47

What are some unknowns of zirconia

Answer 47

it is still a ceramic and not a metal, so long term failure mechanism is still unknown for single crowns

Question 48

What the low-temperature degradation of zirconia

Answer 48

because its metastable there is concern about transforming over time and creating flaws that lead to failures

Question 49

How long has zirconia been used as a substructure and what has been found with fractures

Answer 49

10-15 years | minimal fracture

Question 50

How long has zirconia been used for FCZ and what has been found with fractures

Answer 50

about 4 years | few reported issues

Question 51

What are the steps to cement LDS and LRGC (leucite and lithium based)

Answer 51

etch ceramic with HF acid apply silane dual cure resin cement apply adhesive to tooth

Question 52

This step in cementation of LDS and LRGC preferentially removes glassy phase and leaves a rough surface

Answer 52

acid etch

Question 53

This step in cementation of LDS and LRGC chemically bonds to hydrophilic glass surface to make the surface hydrophobic

Answer 53

silane

Question 54

This step in cementation of LDS and LRGC bonds to silane surface and adhesive on tooth site

Answer 54

dual cure resin cement

Question 55

What is the characteristic of zirconia cementation

Answer 55

zirconia is cemented similar to metal but the inner surface is not rough

Question 56

Why not you etch zirconia to tooth structure

Answer 56

to keep the minerals in