Ceramic system Flashcards
What are ceramics?
Compounds of metallic and non-metallic elements: most frequently oxides, nitrides and carbides
What are traditional ceramics?
China, porcelain, bricks, tiles, glasses
What are the 2 forms of silica?
Amorphous and crystaline
What is the ceramic building block?
Silica SiO2
What are examples of
a) crystalline
b) amorphous silica?
Crystaline e.g. quartz and cristoballite
Amorphous e.g. Alumino-silicate glasses
What is dental ceramic made up of
Mixture of both amorphous and crystaline
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%
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
What do we use feldspathic glasses for?
To make the outside of the crowns with, know it is relatively weak
What are the different dental glass ceramics?
Mica
Lithium disilicate
Canasite
Apatite/Mulite
What is the dental ceramic processing?
Sintering
Casting
Hot processing
CAD-CAM machining
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
What is the baseline aesthetic restoration (the one all others are compared to)
Metal ceramic restorations
In simple terms, how is the metal substructure processed?
Lost wax casting process
In simple terms, how is the cermic veneer made?
Ceramic sintering
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
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
What are the problems with metal-ceramic production?
Not enought space
How much tooth reduction is needed for pfm crown/
1.5mm
0.5mm for metal substructure
1mm for ceramic veneer
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
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
how is the thermal expansion co-efficient different in ceramic and metal?
When unbonded, and when bonded?
TECceramic20 degrees
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
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
