Ceramic system Flashcards by Clelia Serra

What are ceramics?

Compounds of metallic and non-metallic elements: most frequently oxides, nitrides and carbides

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What are traditional ceramics?

China, porcelain, bricks, tiles, glasses

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What are the 2 forms of silica?

Amorphous and crystaline

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What is the ceramic building block?

Silica SiO2

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What are examples of

a) crystalline
b) amorphous silica?

Crystaline e.g. quartz and cristoballite

Amorphous e.g. Alumino-silicate glasses

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What is dental ceramic made up of

Mixture of both amorphous and crystaline

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What was the composition of early dental porcelain?

Ground sea shell - Feldspar 73-85% K2O, Al2O3, 2SiO2
Sand - Quartz, 13-25%, Al2O3 2SiO2
Clay - Kaolin, SiO2, 0-4%

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What are the different dental ceramics?

Feldspathic glasses
Leucite reinforced feldspathic glasses
Alumina reinforced feldspathic glasses
Lanthanum glass infiltrated alumina 
Pure alumina 
Zirconia
Glass ceramics

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What do we use feldspathic glasses for?

To make the outside of the crowns with, know it is relatively weak

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What are the different dental glass ceramics?

Mica
Lithium disilicate
Canasite
Apatite/Mulite

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What is the dental ceramic processing?

Sintering
Casting
Hot processing
CAD-CAM machining

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Because feldspathic ceramic is weak, what 3 ways can it gain support

Metal substructure e.g. pfm
High strength cermic substructure - have zirconia
Bond to the tooth, so tooth is substructure e.g resin bonded crown

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What is the baseline aesthetic restoration (the one all others are compared to)

Metal ceramic restorations

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In simple terms, how is the metal substructure processed?

Lost wax casting process

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In simple terms, how is the cermic veneer made?

Ceramic sintering

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In detail what is the production process of the metal substructure?

Take model of prepated tooth (dye)
Mock up cement layer underneath
Put layer of wax over the top
Alter the margins, design the substructure
Look in compatision to adjacent teeth
Wax then converted into metal
Put on sprew and funnel, place a casting ring around it and fill with plaster of paris
Heat up in casting crucible
Shoot metal into mould - wax is converted into metal
Trim up to condition the surface for the ceramic to bond to the surface

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In detail what is the production for the ceramic veneer to go on top of the metal substructure?

Take the powders and mix with modelling liquid
Paint the first opaque layer on, fire in the furniss, put on opaque proper to mask out the underlying metal substructure
3 firings:metal, first opaque then second opaque
Put the ceramic proper on and build up full contour then fire
The trim do fits, mark contact points
Put glaze on ceramic

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What are the problems with metal-ceramic production?

Not enought space

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How much tooth reduction is needed for pfm crown/

1.5mm
0.5mm for metal substructure
1mm for ceramic veneer

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What are the clinical metal-ceramic problems?

Aesthetics
Metal substructure prevents light transmittance
Often appear opaque at the cervical 1/3
Metal margin can be seen - could overbuild the ceramic but this could cause blanching of the gingiva

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What are the technical problems with metal-ceramic?

Metal-ceramic bond is tempremental
Metal-ceramic junction - abrasive and unhygienic
Metal-ceramic compatibility - thermal expansion co-efficient, shrinkage of materials when cooled down to room temp, if shrink at different rates they will fall apart
support fot ceramic can be well made or not

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how is the thermal expansion co-efficient different in ceramic and metal?
When unbonded, and when bonded?

TECceramic20 degrees

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To prevent the ceramic veneer from cracking due to different TEC’s what can be done?

TEC of ceramic must be equal or slightly less that that of metal therefore can ass leucite

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What is the TEC of
Metal
Ceramic
Leucite

Metal = 13-14ppm/degreeC
Ceramic = 8ppm/degreeC
Leucite = 23ppm /degreeC

Why use CAD?

Can resolve some of the labour intensive design problems and labour saving Easier to make crowns which are joined together, if used lost wax technique would need lots of sprews

what is wax printing? | How does it work?

Print out lots of restorations at one time | Laser sintering unit, put down a bed of fine powder and laser sinters a layer

What are the indications for PFM?

Single unit restorations Multiple unit bridges Support for partial dentures

What are the variants of PFM?

``` Metal type: bonding alloys, ceramic can bond to them High Au content alloys Au-Pd alloys Pd-Ag alloys NiCr CoCr ```

What are the different substructures that can give the ceramic high strength? (both gone and still used today?)

Alumina reinforced ceramic core - gone Glass infiltrated materials (lanthanum glass) - gone Pure alumina substructures - gone Zirconia

What was the first high-strength ceramic substructure restorations?

Porcelain jacket crown Alumina reinforced ceramic core Vita (Vitadur N)

What were the problems with alumina reinforced core?

``` Good aesthetics but opaque core Strength 80 Mpa Tooth reduction (a lot of reduction) Non-adhesive, luted into place Pt foil technique - poor marginal fit ```

What were the 3 variants of glass infiltrated materials - vita in-ceram?

3 variants vary by the strength of translucency: Spinell Alumina Zirconia - alumina/zirconia mix

How were the glass infiltrated materials made?

First by slip casting, then CAD CAMD

Why were glass infiltrated materials never that good?

because it is technique sensitive

What was the strength of glass infiltrated materials compared to the PJC?

All the different in-ceram stronger than PJC | PJC only 80-100MPa

What did all pure alumina sub-structures e.g. Procera All-ceram rely on? What is the strength of pure alumina substructures?

CAD/CAM production | 700MPa

Why is zirconia used as a substructure material?

``` Many available In-house milling available stained prior to sintering Various translucencies Can be used as monolithic material - can make the whole restoration out of it ```

What is required to the zirconia after firing?

Sintering for 10 hours | Extended sintering times for veneering ceramics

What is the strength of zirconia?

500-1200MPa

What are the problems with using zirconia as a sub-structure?

Initial sintering time issue Bond between veneering ceramic and zirconia not as good as ceramic and metal Large units have long sintering times Adjustment/removing and endo are all difficult to do

What are indications for using zirconia?

Strength Aesthetic substructure and veneer Combination work: RPD, support for RPD

What are the different resin bonded restorations?

``` Veneers Dentine bonded crowns Inlays Onlays Partial crowns All made from a material that can be bonded to the tooth structure ```

What are resin bonded restorations produced from?

Feldspathic glass (shot-blast and bond) Leucite glass ceramic Lithium disilicate

What is the strength of the Feldspathic resin bonded restorations?

150MPa

What are the problems with making feldspathic resin bonded restorations

Refractory model production Duplication of dye may compound errors Lack of supporting structure results in fragile restoration, particularly at margins

What are the limitations of feldspathic resin bonded restorations?

Produce single units only | Weak therefore only used for anterior teeth

what is the strength of leucite glass ceramic e.g. IPS empress and empress CAD?

180MPa

What is the lithium disilicate half-way between?

high-strength and resin bonded crown

What are examples of the lithium disilicate? | What is the strength

IPS e.max press and e.max CADCAM | 400-500MPa

What are the different ways emax can be processed?

Pressed, sintered - CADCAM or lost wax

What are the different ways emax can be used?

Substructure of veneer Monolithic Resin bonded - zirconia luted into place

What is the IPS e.max CAD CAM production process?

Set margin Cement lute design veneer

What are the associated materials with lithium disilicate (e.max)?

IPS e.max zircad: zirconica (milled) | IPS e.max ZirPress: fluorapatite glass-ceramic to press over zirconium oxide

What are the prep requirements for e.max?

No sharp corners

What are the different hybrid materials that are coming (part polymer/part ceramic)?

Vita Suprinity - zirconia reinforced with lithium disilicate - 480Mpa Dentsuply: Celtra - pressing version Vita enamic: ceramic 86% and polymer 14% 160 MPa Lava ultimate

What can intra-oral scanners be used for?

``` Can get data into software package: CAD CAD efficient for substructure design Available for complete dentures Efficient for RPD design Can make models Articulation ```

What is the different scanning advanced manufacturing for metals?

``` Wax milling - subtractive Wax printing - additive Metal milling - subtractive Partially sintered metal milling selective laser melting ```

What is the different scanning advanced manufacturing dor ceramics?

Soft state milling Hard state milling 3D printing - stereolithography, thermal deposition