L4 ZIrconia

Question 1

ceramics

Answer 1

man made solid objects formed by baking non-metallic inorganic minerals at high temperatures

Question 2

zirconia (makeup)

Answer 2

zirconium oxide + yttrium oxide

Question 3

transformation toughening

Answer 3

tetragonal –> monoclinic

increase in size (3-4%)

Question 4

types of strength transformation

Answer 4

tensile –> compressive

Question 5

ability of zirconia to arrest crack propagation by changing its phase at the crack’s edges from _____ to _____. thus, the size of the molecules ____, and ____ stresses are replaced by _____ stresses

Answer 5

tetragonal
monoclinic
increase
tensile
compressive

Question 6

flexural strength of zirconia compared to enamel + dentin

Answer 6

higher

Question 7

fracture toughness of zirconia compared to enamel and dentin

Answer 7

higher

Question 8

why zirconia?

Answer 8

1. the widespread use of CAD/CAM
2. less expensive and less time consuming (when compared to PFM restorations)

Question 9

monolithic zirocnia

Answer 9

classified by the amount of yttria

the ENTIRE crown is made of zirconia (no porcelain)

Question 10

layered zirconia

Answer 10

multiple different layers

Question 11

the key to classifying dental zirconia is _____

Answer 11

the yttria content

Question 12

monolithic zirconia 3Y - yttria content

Answer 12

3 mol %

Question 13

monolithic zirconia 3Y - tetragonal vs cubic

Answer 13

> 85% tetragona
<15% cubic

Question 14

monolithic zirconia 3Y - strength and translucency

Answer 14

high strength
low translucency

Question 15

monolithic zirconia 3Y - good to use for…

Answer 15

posterior single unit crowns
FDP

DO NOT USE in highly esthetic areas

Question 16

monolithic zirconia 3Y - preparation

Answer 16

0.5-0.8mm margin - rounded shoulder or heavy shamfer

0.6mm occlusal reduction (manufacture)
0.7-1mm occlusal reduction (studies)

Question 17

monolithic zirconia 4Y - yttria content

Answer 17

4 mol%

Question 18

monolithic zirconia 4Y - tetragonal vs cubic

Answer 18

75% tetragonal
25% cubic

Question 19

monolithic zirconia 4Y - strength and translucency

Answer 19

lower strength compared to 3Y
acceptable translucency

Question 20

monolithic zirconia 4Y - good to use for…

Answer 20

single unit restorations (premolar area)

Question 21

monolithic zirconia 4Y - preparation

Answer 21

0.8-1mm margin
1mm occlusal reduction (manufacture)
1.2mm occlusal reduction (studies)

Question 22

monolithic zirconia 5Y - yttria content

Answer 22

5 mol%

Question 23

monolithic zirconia 5Y - tetragonal vs cubic

Answer 23

<50% tetragonal
>50% cubic

Question 24

monolithic zirconia 5Y - strength and translucency

Answer 24

low strenght
high translucency

Question 25

monolithic zirconia 5Y - good to use for

Answer 25

anterior crowns

Question 26

monolithic zirconia 5Y - preparation

Answer 26

1mm margin 1mm occlusal reduction (manufacture) 1.5mm occlusal reduction (studies)

Question 27

layered zirconia - makeup

Answer 27

porcelain fused to zirconia (PFZ)

Question 28

core and outer layer of layered zirconia

Answer 28

core = 3 mol% zirconia outside = porcelain

Question 29

strength and translucency of layered zirconia

Answer 29

high strength low translucency

Question 30

dimensions of core and porcelain (layered zirconia)

Answer 30

0.6mm core 1.2mm (<2mm) porcelain

Question 31

what happens if there is more than 2m of unsupported porcelain?

Answer 31

porcelain chipping

Question 32

multi-shade layered zirconia

Answer 32

yttria content is the same throughout restoration has different shades!

Question 33

multi-yttria layered zirconia

Answer 33

the yttria content is different throughout made of same shade DIFFERENT TRANSLUCENCIES

Question 34

strength and translucency of multi-yttria layered zirconia

Answer 34

variable strength variable translucency because of different yttria contents!

Question 35

in theory, where should the stronger zirconia go in multi-yttria layered zirconia

Answer 35

stronger phase zirconia at cervical part because it increases fracture resistance

Question 36

in reality, what happens when the weaker zirconia phase is at the occlusal part?

Answer 36

decreases fracture resistance

Question 37

when should you use sodium hydroxide in zirconia cementation?

Answer 37

after trying in restoration

Question 37

when should you use sodium hydroxide in zirconia cementation?

Answer 37

after trying in restoration

Question 38

why use sodium hydroxide for zirconia cementation?

Answer 38

because zirconia has a high affinity to salivary proteins so cleaning it with sodium hydroxide after the try in is necessary

Question 39

bonding protocol for zirconia

Answer 39

APC concept 1. air abrade 2. phosphate monomer 3. cement

Question 40

what kind of cement should be used for zirconia?

Answer 40

dual or self/chemical cure