4. Dental Porcelain Flashcards
DENTAL PORCELAIN
Defn: Porcelain
White transluscent ceramic that is fired to a ____ state.
Non ____ glasses ____ porcelain
glazed
crystalline
feldspathic
DENTAL CERAMICS
Solid materials composed of inorganic non-____ compounds
____, clay products, ____, glass etc.
metallic
pottery
glass
Classification of Dental Ceramics
• Today we are talking about PFMs
◦ You can have wrought alloys as you substrate for PFMs and crowns
• There are all ceramic crowns that include reinforced ____ and other veneering ceramic
• This is a general picture of ceramic crowns
ceramic
Advantages of Dental Ceramics Excellent \_\_\_\_ \_\_\_\_ appearance (esthetics) High resistance to \_\_\_\_ and distortion \_\_\_\_
• Ceramic have high biocompatibility
• They have great esthetics
◦ You can reproduce the natural color of teeth easily
• They have high resistance to wear and distortion, this makes them very durable
biocompatability
natural
wear
durability
Disadvantages of Dental Ceramics
____
Hard, difficult to ____ ____ opposing teeth
Does not bond to ____ base material (acrylic)
Produces ____ sound on contact
High ____
• Does not bond well to denture acrylic
◦ It is hard to use them as ____ teeth
brittleness polish wears denture clicking density denture
Dental Ceramic Restorations PFM porcelains Opaque Body \_\_\_\_ \_\_\_\_ (enamel) \_\_\_\_ \_\_\_\_
• Metal substrate under crown
• Right above the metal substrate is a layer of porcelain called ____ Porcelain
• Right above the Opaque Porcelain is ____ Porcelain
◦ There are different types of Body Porcelain to give a ____ look to the teeth
◦ There are several modifiers that help us produce ____ tooth color
• Why don’t we make the whole crown out of porcelain?
◦ Porcelain is not strong enough and will fracture ◦ ____ substrate is needed for support
dentin
incisal
translucent
modifier
opaque body natural natural metal
All- Ceramic crown
____ Strength Core
Aluminous ____ core CAD/CAM Ceramics
• Here we can see an all ceramic crown
◦ Notice I said “all ceramic” and not “all porcelain”
◦ We have a substrate that is high strength
‣ High strength ceramics are often ____ (Ex: zirconia, alumina)
• Over the high strength core ceramic we have ____ bonded to it, similar to how
porcelain is bonded to metal in a PFM
• More and more all ceramic crowns are being fabricated as CAD/CAM ceramics
• The whole crown can be made of one ____ instead of having other veneering
ceramics placed on them (Ex: all zirconia crowns)
high porcelain crystalline porcelain ceramic
Uses of Porcelain \_\_\_\_ teeth Jacket crowns \_\_\_\_ Porcelain-fused-to-metal crown and bridge work \_\_\_\_
• Jacket crowns are all ____ crowns
• Porcelain is a very translucent ceramic, therefore very easy to reproduce tooth
____
◦ Useful in making veneers
denture inlays veneers porcelain shades
General Composition of Porcelain
Feldspars 75-85% (Na2O.Al2O3.6SiO2/ K2O.Al2O3.6SiO2)
Alumina 0-10%
Quartz 12-22%
Kaolin 3-5%
(Al2O3-SiO2-H2O - clays)
Metallic oxides & pigments < 1%
• The main component of porcelain is ____
◦ Naturally available, it is a mined product
◦ There are 2 types, the first is ____ Feldspar (has sodium) ◦ The second type is ____ Feldspar (has potassium)
• Alumina and quartz are ____ materials that are added to improve ____ of porcelain
• Kaolin is a clay and makes the material ____
• Metallic oxides and pigments give us different ____
feldspar soda potash crystalline strength moldable shades
Composition of dental porcelains
• The point of this slide is to show that when we add sodium oxide and potassium oxide to our porcelain, we are reducing the ____
◦ As sodium oxide and potassium oxides increase, we have a lower ____
◦ We need this for porcelains that are fused to metals
firing temperature
fusion temperature
Structure of Porcelains
Structure of SiO2 glass and the
Effect of adding Na2O
• When we add sodium oxide or potassium oxide, we are opening up the ____ [bottom pic]
◦ Reducing firing temperature
◦ The added oxide also increases the ____ of the porcelain
structure
coefficient of thermal expansion
Role of Components
Feldspar
____
Oxides of ____,Sodium, and Calcium
____ formation
Quartz (SiO2)
Stability at high ____, strength
Alumina (Al2O3)
Increased ____ & viscosity
Kaolin (Al2O3-2SiO2..2H2O) ____, moldability
• Silica forms the ____
• The oxides break up the matrix, decrease the firing temp, and increase
the coefficient of thermal expansion
• Quartz and alumina provide strength and stability at high temperatures
• Kaolin is a clay material that provides ____
SiO2 potassium leucite temps strength binder matrix moldability
Classification of Dental Porcelains
Ultra low fusing < ____ F
• Which porcelain will you select for PFM crowns? ____ Fusing ◦ In order to process our porcelain, we stuck the porcelain on the
metal frame work and then it is heated
◦ We want a porcelain that fuses at a temperature that is lower than
the ____ of our alloy
1600
ultra low
melting point
Manufacture of Porcelain Powder Fritting
Heat mixture to form glass Leucite crystals
Quench to form a ____
Grind to desired particle size
Add ____ to form desired porcelain
Opaque, dentin, enamel & color modifiers
• Porcelain powder is made by mixing varying amounts of oxides in order to achieve different properties
◦ They are then heated to form a glass
‣ Leucite crystals can form during this process if there are not appropriate contr
• They can increase the ____ ◦ Mixture is then quenched (cooled suddenly)
‣ Pulverized into a powder call a frit
• The main metal oxide that is used to obtain different shades is ____
◦ Depending on how the iron oxide is fabricated, you can get many different shades
frit
metal oxides
coefficient of thermal expansion
iron oxide
Manufacture of Porcelain Powder
High fusing porcelains Feldspars melt and form \_\_\_\_ phase Final Microstructure 85% \_\_\_\_ phase 15% \_\_\_\_ quartz + alumina
Medium and low fusing porcelains
Fusion of glassy ____ powder particles
High content of ____ phase
• For high fusing porcelains, there will be an 85% vitreous phase with 15% quartz and alumina present
◦ These crystalline components ____ the porcelain
glassy vitreous crystalline frit vitreous strengthen
Microstructure of Dental Porcelain
This shows the micro structure of a crystalline material that is reinforcing the vitreous silicone dioxide phase.
When cracks propagate, they have to go through the high strength ____ faces. This is how they increase the strength of the porcelain
cystalline
Fabrication of porcelain restorations
Use of Glassy ____ powder particles
Little or no ____ reactions Reduced firing ____
more ____ composition than without fritting
• When making a PFM, want to use the powder that has been fabricated previously from the ____
◦ The components have already been heated, fused, and pulverized
◦ The reason is that when you do this initially, there will be a high amount of shrinkage
‣ So if it is pulverized already, we reduce the amount of ____ in the final restoration
◦ Also, when we are firing the porcelain on the metal, there are no ____ reactions taking place
frit pyrochemical shrinkage uniform frit shrinkage chemical
Characteristics of PFM Porcelains
Opaque Porcelains Addition of \_\_\_\_ oxides, TiO, SnO, ZrO, CeO \_\_\_\_ refractive index, Light scattering \_\_\_\_ particle size
____ metal surface
Masks ____ color
Initiates ____ development Thickness ____mm
insoluble high fine wets metal shade 0.1-0.5
Characteristics of PFM Porcelains
Body Porcelains
Dentin
Color of natural ____
____ range of shades
Enamel/Incisal
____
____ shade range
Translucent Porcelains Veneer over entire ____ Depth, enamel like translucency
dentin wide translucent restricted porcelain
