4. Dental Porcelain Flashcards by J L

DENTAL PORCELAIN
Defn: Porcelain
􏰈White transluscent ceramic that is fired to a ____ state.
􏰉Non ____ glasses 􏰊____ porcelain

glazed
crystalline
feldspathic

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DENTAL CERAMICS
􏰉Solid materials composed of inorganic non-____ compounds
􏰊____, clay products, ____, glass etc.

metallic
pottery
glass

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Characteristics of PFM Porcelains
􏰈Stains &amp; Glazes
􏰉High \_\_\_\_ oxide content 􏰉colorant oxides
􏰉\_\_\_\_ oxides
􏰉High \_\_\_\_, Low fusing glass

􏰈Glaze
􏰉____ low fusing porcelain 􏰉____ appearance of enamel

Stain is designed to be very ____
◦ They will have high ____ and sodium oxide (reduce fusion temp of porcelain) ◦ Iron oxide is the main component giving us the shades we desire
◦ Because of the high alkali and oxide content, they have high fluidity and low fusing
temperatures
• Glazes are typically colorless and give a glossy appearance
◦ Good for ____ edge where teeth should be translucent

alkali
metallic
fluidity

colorless
glassy
fluid
potassium
inicisal

he Porcelain-Metal System 􏰈System requirements

􏰉____ requirements 􏰉____ requirements 􏰉Mechanisms of ____

metal
porcelain
bonding

Porcelain-Metal Restorations

􏰈Alloy requirements
􏰉High ____ temperature
􏰉High ____ resistance
􏰉Adherence controlling elements to form surface oxides: ____, Sn, ____
􏰉Coefficient of thermal expansion ____ (higher than porcelain)
􏰊 reduce stress on porcelain

• The ally should have a high fusion temperature because the porcelain is heated on top of it ◦ Don’t want our porcelain fusing temp to get too close to ____ of alloy
• High sag resistance
◦ As you approach the melting temp of the alloy, it will begin to sag in the middle ◦ We want an alloy with a high resistance to this
• The adherence controlling elements form an oxide layer on the alloy that the porcelain can bond to
• We want a metal that has a slightly high coefficient of ____ than the porcelain ◦ Stress on the porcelain will be reduced when in function

fusion
sag
Fe
In
matching
melting temp
thermal expansion

Porcelain Requirements for PFM
􏰈Low \_\_\_\_ ( High \_\_\_\_ metal content Na2O, K2O and CaO)
􏰈Opaque with high \_\_\_\_ to mask metal
􏰈Matched \_\_\_\_ 
􏰈Non \_\_\_\_

• Non greening
◦ Found in alloys that contain ____
◦ Green tint can be seen at ____
◦ This has been corrected in alloys used today

fusing
alkali
metallic oxides
coefficient of thermal expansion
greening
silver
margins

Porcelain Requirements for PFM

Thermal expansion
􏰈Coefficient of thermal expansion of metals change ____ from firing temp to room temp
􏰈 Porcelain changes a lot ____

􏰈 Alloy should ____ slightly
more than porcelain
􏰉put porcelain under ____

The coefficient of thermal expansion of the metal and porcelain behave differently ◦ The job of the manufacturer is to match the porcelain to the alloy correctly
The alloy should contract slightly more than the porcelain to put porcelain under compression and reduce tensile stresses on the porcelain

little
more
contract
compression

Porcelain Requirements for PFM 􏰈Repeated firings cause ____ 􏰉 Clouding 􏰉____ formation may also occur 􏰊change in coefficient of ____ • Potential problem, technician may make multiple additions to porcelain resulting in repeated firings ◦ This can cause devitrification ‣ ____ of porcelain • Once crystals begin to form, porcelain gets ____ • Leucite can significantly change the coefficient of thermal expansion or porcelain

``` devitrification leucite thermal expansion crystallization cloudy ```

Stresses on PFM Crown 􏰈Loaded PFM crown 􏰉Metal under ____ 􏰉Porcelain should be under ____ 􏰈Stresses at metal porcelain junction 􏰉Design of PFM * This is what we are talking about when we say we are putting porcelain under compression * This ensures that the bond between the metal and porcelain is durable * High stresses at the ____ can lead to crown failure [bottom pic]

tension compression junction

Mechanisms of Porcelain Bonding ____ forces ____ retention • Van der Waals forces ◦ Weak bonding between the oxides of the ____ and the oxides of the ____ • Mechanical retention ◦ [top right pic] high magnification of the metal surface ‣ Very ____, powder particles will seep in resulting in increased retention

``` van der waals mechanical metal porcelain rough ```

Mechanisms of Porcelain Bonding 􏰈 Chemical bonding 􏰉 ____ • One of the properties of the metal is adherence controlling elements (____, Sn, In) ◦ When gold or noble based alloys are heated, the oxides in the metal bond ____ to the oxides in the porcelain (chemical compatibility) • We can see here iron oxide and silicone dioxide in porcelain reacting to form chemical bonds that help with bonding of porcelain to metal

iron oxide + silica Fe chemically

Mechanisms of Porcelain Bonding Oxide layer on ____ bonds chemically to oxides of ____ porcelain * Oxide layer on metal bonds to the opaque layer of the porcelain * [right pic] shows the mechanical interlocking * [bottom left pic] shows the chemical bonding

metal | opaque

Mechanisms of Porcelain Bonding 􏰈 Chemical bonding 􏰉 +____ 􏰉 ____ quality 􏰈 ____ bonding 􏰈 ____ bonding • This shows the contributions of the different mechanisms of bonding • [left column] Experiment with a gold alloy not containing the adherence controlling elements ____, ____, and ____ (THIS IS THE 3rd or 4th TIME HE HAS REPEATED THESE!) • Chemical bonding is increased with the adherence controlling elements ◦ The most important contribution to the bonding is ____ bonding ◦ Must follow the right techniques to obtain as much chemical bonding as possible

van der waals oxide compression mechanical iron tin indium chemical

Compression Bonding • When porcelain has been designed to be under compression [bottom], the compression force must be overcome before the ____ are seen on the surface of the porcelain ◦ This is the reason why we want porcelain under ____ (so it survives tensile stress)

tensile forces | compression

Bond Strength and Characterization 􏰈 ____ interlocking 􏰈 ____ bonding 􏰈 Rely on mechanical ____ • You can take a PFM alloy and bond your opaque porcelain to it • You can make a loading device like this that can determine how much force is needed to pull the metal out ◦ Depending on whether the alloy contains adherence controlling elements or not, you can determine how much of the bond strength is from having chemical oxides on the surface

mechanical chemical retention

PFM sequence ____ cleaning ____ • Here we have a 3 unit bridge, notice how the die was painted with a spacer • [top right] we have our metal undercasting on the surface ◦ The surface is cleaned of all debris and then ground • After it is ground, it is placed in oven for degassing ◦ Degassing - heating to create an ____ on the metal surface • After degassing, ____ layer is stuck onto metal [bottom left] ◦ Place in oven and heat to prescribed temperature for firing • Once opaque layer is fired, ____ layer is placed [bottom right]

``` metal surface degassing oxide opaque dentin ```

Application and Condensation of Porcelain 􏰈Methods 􏰉____ application 􏰉gravitation 􏰉____ 􏰉vibration 􏰈Condensation of powder particles 􏰉withdrawal of ____ 􏰉surface tension packs powder • You can mix the porcelain powder and distilled water and apply directly to metal surface a brush ◦ Other methods: gravitation, spatulation, vibration • Once the powder/water solution has been applied, you must blot off moisture on surface with ____ ◦ This helps ____ the powder in place

``` brush spatulation water paper towel pack ```

Porcelain Powders 􏰈Powders have a range of particle sizes 􏰉40-49% porosity after ____ pressure compaction (wet vibration in mold) 􏰉 􏰉30% porosity after ____ at 14.5 tones/in2

low | compaction

Firing and Microstructural Changes 􏰈Initial preheating 􏰉____ water removal to prevent void formation or fracture 􏰈Sintering 􏰉flow and fusion of adjacent particles 􏰊 ____ and change in pore shape • Once the powder has been applied, you go through different stages of heating • Place unit under heating chamber of oven and wait for a slow evaporation of the water • After water has evaporated, you raise the unit into the heating chamber and it goes through the ____ process ◦ Sintering - ____ of adjacent particles ◦ ____, change in pore shape (decrease in porosity)

``` slow shrinkage sintering fusion shrinkage ```

``` Sintering of Porcelain 􏰈Important factors 􏰉 ____ 􏰉surface tension 􏰉 ____ ``` 􏰉particle size 􏰉Ambient ____ (air vs. vacuum) 􏰉Biscuit stage * This shows porcelain powder that has been sintered * The particles are not exactly combined, but they are in close contact * [reads important factors] * After the ____ stage of firing, the surface feels crunchy and is described as the ____ stage of firing

``` temperature viscosity pressure first biscuit ```

Shrinkage & Porosity 􏰈Shrinkage during firing- 30% 􏰉Loss of ____ during drying 􏰉 ____ 􏰈Porosity: 􏰉Air-fired porcelains - 7% 􏰊best ____ with large grain 􏰉Vacuum-fired porcelains <1% porosity 􏰊 best translucency with ____ grain sizes 􏰊 pores too small to interfere with light ____ • Shrinkage results from loss of water and the sintering process ◦ Because of this, technicians must ____ ceramic ‣ Takes a lot of practice • Different porcelains are manufactured for air firing and vacuum firing ◦ You want to use a ____ grain porcelain powder for air firing ◦ In vacuum fired, the pores are too ____ to interfere with light transmission and do not with esthetics

water sintering translucency small transmission overbuild large small

Vacuum vs Air Fired Porcelains | 􏰈Note differences in ____

porosity

PFM Sequence * After the dentin porcelain is fired, this is what we get [top left] * We then apply ____ and glazes for a natural appearance

stains

Porcelain Firing Cycles 􏰈Degassing ~ ____oC for 5 min ``` 􏰈Porcelain Firing 􏰉Firing temperatures 􏰉Rate of temp ____ 􏰉____ time 􏰉Cooling rates 􏰉Restoration is placed under ____ ``` * The first step after cleaning the casting is to heat it (____) * [reads slide] * Hold time - how long unit is held at a given temp

``` 1000 rise hold thermocouple degassing ```

Glazing 􏰈Masks surface ____ in fired porcelain 􏰉provides smooth surface 􏰉minimize ____ debris retention and plaque formation 􏰉increases ____ 􏰈 Self-glazing 􏰉Controlled firing ____ 􏰈Glaze powder with separate firing cycle • After dentin porcelain, we apply a glaze ◦ [reads benefits of glazing] • Self-glazing - Some dentin porcelains can be sent through a ____ firing cycle to produce a glaze • Or you can apply a specific glaze porcelain to the surface with its own firing schedule

defects food strength schedule second

Types of Bond Failures • This is important in diagnosing what went wrong • If you can identify the type of failure, you can decide whether you want to fix it or remake the crown • If the failure is on the ____ surface there is nothing you can do and you must remake a crown • Failure between metal and porcelain = poor ____ formation on metal surface • Failure within the porcelain can be fixed with ____ • Metal oxide-metal oxide - depending on the thickness of the oxide, you may be able to bond ____ to it to restore • Most times you must ____ crown because bonding techniques do not work often

metal oxide composite composite

Bond failures • [top right] complete exfoliation of porcelain from metal surface ◦ Failure happened within ____ on surface of metal ◦ We must ____ this crown

oxide | remake

Oxides on PFM alloys Noble Metals A. 􏰉 ____ 􏰉 Pd-Cu 􏰉 ____ 􏰈B. 􏰉 ____ 􏰉 Pd-Ag • This shows that different alloys can give different quality of oxides on surface ◦ Copper containing alloys form a ____ oxide that is hard to mask ‣ undesirable in terms of oxide quality • Alloy on right is much easier to ____

Au-Pd-Ag Pd-Ag dark black mask

Oxides on PFM alloys Base Metals 􏰉 ____ 􏰉 Ni-Cr 􏰉 ____ • Remember, we mentioned that Beryllium is added to base metal alloys because they improve the ____ of the metal, they also help to improve the quality of the ____ on the metal surface ◦ Easy to ____ ◦ Easy to bind to ____

``` Ni-Cr-Be Co-Cr flow oxide mask porcelains ```

Improving Oxide Quality 􏰈Metal Deposition 􏰉Gold deposition followed by ____ to provide an oxidized surface, also liven porcelain ____ 􏰈Surface ____ for reducing oxide thickness on base metals 􏰈Improved bond strength and esthetics by limiting formation of ____ oxides • Because of the poor looking oxide quality on some of the alloys, there are techniques (metal deposition) used to improve the surface ◦ Gold is applied, then tin ◦ Tin is oxidized on surface, gives lively porcelain color similar to what you would get when bonding to a gold alloy • Reducing oxide thickness on base metals ◦ Base metals, by nature of being a base, ____ easily and form thick oxides on the surface ‣ If oxide is too ____, bond will fail • Bond strength and esthetics are improved by limiting oxides that are too ____ and too ____

``` tin color coatings dark oxidize thick dark thick ```

All- Ceramic Crowns ``` 􏰈Ceramic core material 􏰈High strength 􏰉____ porcelain 􏰉____ reinforced 􏰉____ infiltrated Alumina 􏰉Cast ____ (Dicor) 􏰉Crystalline ceramics 􏰊 ____ ``` * In an all ceramic crown, instead of the metal (in a PFM), we have a high strength ____ material such as [reads list] * We will learn more about all ceramic crowns in 3rd year

``` aluminous leucite glass glass zirconia ceramic ```