Porcelain

Question 1

Classify porcelain according to fusing temperature

Answer 1

High fusing , 1300 or above
Medium- fusing , 1101-1300
Low-fusing 850-1100
Ultra low fusing

Question 2

Feldspar is

Answer 2

The main raw ingredient crystalline opaque material

Question 3

Phases of feldspar melting

Answer 3

Glossy , has amorphous structure surrounding a crystalline phase consisting of leucite

Question 4

Feldspar decomposes to form

Answer 4

Glass and leucite ( role in coefficient of thermal expansion + strength of the porcelain )

Question 5

Silica (quartz) contribute to

Answer 5

Stability of the porcelain during heating

Question 6

Kaolin role

Answer 6

Opaqueness property to the porcelain

Question 7

Fluxes and glass modifiers role

Answer 7

Lower the fusion temp and increase the flow

Question 8

Sodium oxide and potassium oxide are called

Answer 8

Glass modifiers

Question 9

To increase opacity use

Answer 9

Opacifiers - tin oxide,zirconium oxide , titanium oxide

Question 10

Cerium oxide gives

Answer 10

Fluorescence property

Question 11

Glaze

Answer 11

Fired porcelain is porous and can not be polished, therefore a low fusing glass is added to the surface of the body , resulting in glossy surface

Question 12

Jacket crown porcelain has the property of ..

Answer 12

Self glazing

Question 13

Aluminum porcelain contains around…….. in the core which can ….

Answer 13

40 % crystalline alumina , double its strength

Question 14

Aluminum porcelain appliances

Answer 14

1- PFM
2- all ceramic crown
3- denture teeth

Question 15

Using zinc phosphate can change the crown shade there for using….or …. Gives better results

Answer 15

Silica-phosphate or glass-ionomer

Question 16

Types of porcelain used in the fabrication of restoration

Answer 16

Opaque / core , to mask
Body /dentin , to make up the bulk
Enamel , translucent layer

Question 17

Condensation is

Answer 17

Process of packaging and removing excess water to minimize porosity

Question 18

Condensation methods

Answer 18

Vibration, spatulation , brush technique
* different size better condensation

Question 19

Sintering is

Answer 19

Partial fusion of adjacent surfaces rather than complete fusion

Question 20

In the final firing glazing is done , and can be achieved by ..

Answer 20

Self glazing porcelain
Add-on glazing
* rapid cooling is avoided

Question 21

Requirements of alloys used for PFM

Answer 21

1-coefficient of thermal expansion, alloy should be similar to porcelain
2- alloy should be rigid
3- most form strong bonding
4- melting temp of alloy should be higher then firing temp of porcelain

Question 22

Requirements of ceramic used for PFM

Answer 22

1- must fuse at low temp
2- must have melting temp of alloy compatible with the alloy used for PFM
3- must withstand oral cavity environment

Question 23

The nature of metal-to-ceramic bond is divided to

Answer 23

Mechanical
Compressive
Chemical

Question 24

Advantages and disadvantages of porcelain

Answer 24

Advantages
High esthetic properties
Dimensionally stable
Poor conductor to heat

Disadvantages
Brittle
Not ductile
Low shear and tensile strength

Question 25

Difference between acrylic and porcelain teeth

Answer 25

Acrylics
Made from heat curing acrylic resin
Resilience
Light weight
Change in color
Low abrasion
Natural sound

Porcelain
Made from high fusing porcelain
Brittle
Heavy
No change in color
High abrasion
Clicking sound on use