Porcelain Flashcards
Classify porcelain according to fusing temperature
High fusing , 1300 or above
Medium- fusing , 1101-1300
Low-fusing 850-1100
Ultra low fusing
Feldspar is
The main raw ingredient crystalline opaque material
Phases of feldspar melting
Glossy , has amorphous structure surrounding a crystalline phase consisting of leucite
Feldspar decomposes to form
Glass and leucite ( role in coefficient of thermal expansion + strength of the porcelain )
Silica (quartz) contribute to
Stability of the porcelain during heating
Kaolin role
Opaqueness property to the porcelain
Fluxes and glass modifiers role
Lower the fusion temp and increase the flow
Sodium oxide and potassium oxide are called
Glass modifiers
To increase opacity use
Opacifiers - tin oxide,zirconium oxide , titanium oxide
Cerium oxide gives
Fluorescence property
Glaze
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
Jacket crown porcelain has the property of ..
Self glazing
Aluminum porcelain contains around…….. in the core which can ….
40 % crystalline alumina , double its strength
Aluminum porcelain appliances
1- PFM
2- all ceramic crown
3- denture teeth
Using zinc phosphate can change the crown shade there for using….or …. Gives better results
Silica-phosphate or glass-ionomer
Types of porcelain used in the fabrication of restoration
Opaque / core , to mask
Body /dentin , to make up the bulk
Enamel , translucent layer
Condensation is
Process of packaging and removing excess water to minimize porosity
Condensation methods
Vibration, spatulation , brush technique
* different size better condensation
Sintering is
Partial fusion of adjacent surfaces rather than complete fusion
In the final firing glazing is done , and can be achieved by ..
Self glazing porcelain
Add-on glazing
* rapid cooling is avoided
Requirements of alloys used for PFM
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
Requirements of ceramic used for PFM
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
The nature of metal-to-ceramic bond is divided to
Mechanical
Compressive
Chemical
Advantages and disadvantages of porcelain
Advantages
High esthetic properties
Dimensionally stable
Poor conductor to heat
Disadvantages
Brittle
Not ductile
Low shear and tensile strength
Difference between acrylic and porcelain teeth
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
