Ceramics

Question 1

What type of materials make ceramics that are more amorphous?

Answer 1

-Glass like properties

Question 2

What type of properties make ceramics that are more ordered?

Answer 2

-Crystalline properties

Question 3

What are four properties of classic ceramics?

Answer 3

• High in compressive strength
• Low in Tensile strength
• High in electrical and thermal resistance
• Highly resistant to chemical breakdown

Question 4

T/F Graphite is considered a ceramic and is therefore hard and resists electrical conduction

Answer 4

False

-Is soft and conducts electricity well

Question 5

T/F Zirconia can have very high tensile strength

Answer 5

True

Question 6

T/F Diamond is a ceramic and is not a good thermal conductor

Answer 6

False

-It is a good thermal conductor

Question 7

T/F Ferrites are ceramics that are superconductors and have almost no electrical resistance

Answer 7

True

Question 8

What is a solid transparent plastic made of polymethyl methacrylate known as?

Answer 8

-LUcite

Question 9

What is a white or gray feldspathic mineral composed of potassium and aluminum silicates?

Answer 9

-LEucite

Question 10

What do leucite crystals increase?

Answer 10

-Resistance to crack propagation in ceramics

Question 11

What are three classic ceramics?

Answer 11

• Feldspar
• Quartz
• Kaolin

Question 12

T/F Zirconia is a porcelain

Answer 12

False

it is not

Question 13

What some all ceramic applications?

Answer 13

• Inlays
• Onlays
• Veneers
• Crowns
• FPD

Question 14

What are some all ceramic combinations?

Answer 14

• PFZ
• Porcelain fused to lithium disilicate
• Heat pressed or machined

Question 15

Does glassy/vitreous or crystalline have better optical properties?

Answer 15

-=Glassy vitreous

Question 16

What are the properties of glassy or vitreous ceramics?

Answer 16

• Better optical properties
• Less strength
• Less resistance to crack propagation
• Less ordered in structure

Question 17

What are the properties of crystalline ceramics?

Answer 17

• Better mechanical properties
• More strength
• More resistance to crack propagation
• More ordered in structure

Question 18

Is feldspathic porcelain more vitrous or more crystalline?

Answer 18

-Vitreous

Question 19

What type of ceramic is more cystalline?

Answer 19

-Zirconia

Question 20

What is zirconia?

Answer 20

-Oxide of the metal zirconium

Question 21

What are the two forms of zirconia?

Answer 21

• Zircon (zirconium silicate

- Baddeleyite (zirconium oxide)

Question 22

What is the strongest form of zirconia?

Answer 22

-Tetragonal

Question 23

What are the three crystalline phases of zirconia?

Answer 23

• Monoclinic
• Tetragonal
• Cubic

Question 24

What is added to the tetragonal phase of zirconia to stabilize it at room temperature?

Answer 24

• yttria oxide

- Cerium oxide

Question 25

What is the most opaque of the three forms of zirconia?

Answer 25

-Tetragonal

Question 26

What increases resistance to low-temperature aging degradation of zirconia?

Answer 26

- Yttria oxide | - Cerium oxide

Question 27

What does a crack in the zirconia do?

Answer 27

-Induces a tetragonal to monoclinic phase change causing the compressive forces to terminate crack propagation

Question 28

Does the yttria or cerium have a higher fracture toughness?

Answer 28

-Cerium

Question 29

Is the Yttria or cerium resistant to low temperature aging degradation?

Answer 29

-Cerium

Question 30

What causes zirconia surface degradation?

Answer 30

-Transformation from the tetragonal phase to the monoclinic phase

Question 31

T/F Highly polished zirconia is much less abrasive than porcelain

Answer 31

True

Question 32

What are the factors that increase translucency of zirconia?

Answer 32

- Increasing density - Increasing Yittria - Increasing amount of cubic phase - Decreasing Al2O3 - Sintering temp - Heating method - Atmospheric conditions during sintering

Question 33

What does increasing the yittria and increasing the amount of cubic phase do to the zirconia?

Answer 33

-Decreased flexural strength and fracture toughness

Question 34

What decreases the hydrothermal stability of zirconia?

Answer 34

-Decreasing Al2O3

Question 35

What are the things you DO when adjusting zirconia?

Answer 35

- Use fine or medium diamonds - Use light touch - Follow order abrasives - Slow speed handpiece

Question 36

What are things you AVOID when adjusting zirconia?

Answer 36

- Coarse diamonds - Heat - Vibration - Heavy pressure - Non-Diamond abrasives - Skipping abrasives - High speed handpiece