Dental Ceramics

Question 1

what is ceramic?

Answer 1

a non-metallic inorganic materials which is processed by firing at a high temperature

Question 2

what is porcelain?

Answer 2

compositional range of ceramic material made by mixing feldspar, quartz and kaolin and firing at a high temperature

Question 3

what are glass ceramics made out of?

Answer 3

contain feldspar, quartz (silica) and alumina with no or little crystalline phase

Question 4

what are types of dental ceramics classified into?

Answer 4

microstructure

composition

fabrication process

temperature

function

Question 5

what types of dental ceramics are in microstructure?

Answer 5

glass-ceramics (glassy matrix with crystals eg. lithium disilicate)

crystalline ceramics (mostly crystals)

polycrystalline ceramics (entirely crystalline e.g. zirconia)

Question 6

what types of dental ceramics are in composition?

Answer 6

feldspathic ceramics

leucite-reinforced ceramics

lithium disilicate ceramics

alumina-based ceramics

zirconia-based ceramics

Question 7

what types of dental ceramics are in fabrication process?

Answer 7

condensable ceramics

heat-pressed ceramics

machinable ceramics

castable ceramics

Question 8

what types of dental ceramics are in function?

Answer 8

core ceramics

opaque ceramics

veneering ceramics

Question 9

what is the function of feldspar?

Answer 9

forms glass matrix, fuses other components

Question 10

what is the function of quartz?

Answer 10

adds translucency and adds stability

Question 11

what is the function of kaolin?

Answer 11

binds particles, adds opacity

Question 12

what is the function of alumina?

Answer 12

improves mechanical stability

Question 13

what is the function of zirconia?

Answer 13

improves mechanical stability

Question 14

what is the function of metal oxides?

Answer 14

adds colour and optimises aesthetics

Question 15

what are some advantages of zirconia restorations?

Answer 15

dense mono-crystalline homogeneity
biocompatibility

good wear resistance

low thermal conductivity

low bacteria surface adhesion

favourable optical properties (high aesthetics (translucency, colour matching))

Question 16

what are some limitations of zirconia restorations?

Answer 16

long-term instability if in presence of water

veneering compatibility issues

bonding with resin-based luting agents

Question 17

what are some features on the manufacturing process of heat-press

Answer 17

high strength, low porosity (e.g. IPS Empress)

Question 18

what are some features on the manufacturing process of slip-cast?

Answer 18

high toughness, technique sensitive

Question 19

what are some features on the manufacturing process of CAD/CAM milling?

Answer 19

accurate

fast

ideal for zirconia

Question 20

what are the mechanical properties of feldspathic?

Answer 20

60-70 mPa
low strength

Question 21

what are the mechanical properties of lithium disilicate?

Answer 21

around 360 mPa

crack resistance due to crystal orientation

Question 22

what are the mechanical properties of alumina?

Answer 22

around 600 mPa

high modulus, less translucent

Question 23

what are the mechanical properties of zirconia?

Answer 23

more than 1000 mPa

transformation toughening mechanism

Question 24

what are glass ceramics made up of?

Answer 24

feldspar, quartz, alumina with little to no crystalline phase

Question 25

what are some advantages of all-ceramic restorations?

Answer 25

superior aesthetics and high translucency good tissue response biocompatibility conservative facial tooth reduction especially for veneers

Question 26

what are some limitations of all-ceramic restorations?

Answer 26

lack metal substructure for reinforcement substantial tooth reduction for some materials not suitable to support RPD retainers

Question 27

what is the crystal structure of pure zirconia at: room temp around 1200 degrees C around 2700 degrees C

Answer 27

room temp = stable 1200 degrees C = tetragonal 2700 degrees C = cubic