Lecture 13 & 14 - Ceramics (Slides)

8/3/2019 Lecture 13 & 14 - Ceramics (Slides)

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CeramicsCeramics

Dental materialsDental materials

Dent 305Dent 305



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Porcelain (maybe considered as aPorcelain (maybe considered as a

type of glass)type of glass)DrawbacksDrawbacks

BrittleBrittle Low fracture resistanceLow fracture resistance

Wear of opposing tooth Wear of opposing tooth

Difficulty of reDifficulty of re--polishing polishing

after adjustment

Advantages Advantages

Very hard esthetic Very hard estheticmaterial.material.

BiocompatibleBiocompatible

Excellent estheticExcellent esthetic

Low wearLow wear

Stain resistant

after adjustment

Stain resistant



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CompositionComposition

Dental porcelain

Silica (quartz) Kaolin (clay) Feldspar (binder)

Pigments added (in the form of oxides)Pigments added (in the form of oxides)

Iron oxides: brownIron oxides: brown

Copper oxides: greenCopper oxides: green

Titanium oxides: yellowish Titanium oxides: yellowish--brownbrown

Cobalt oxides: blueCobalt oxides: blue

Sugar or starch as binders to help manipulationSugar or starch as binders to help manipulation



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Manufacturing process of Manufacturing process of

porcelain porcelain All constituents are mixed and then fused to All constituents are mixed and then fused to

form a frit. This is broken up by dropping it inform a frit. This is broken up by dropping it incold water. Then its ground into fine powder.cold water. Then its ground into fine powder.

During fusion oxides unite all together.During fusion oxides unite all together.

So during crown production, the technician isSo during crown production, the technician is

simply resimply re--melting the material, no extra fusionmelting the material, no extra fusion

occursoccurs



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Types of porcelains Types of porcelains

Classification based on fusing temperature:Classification based on fusing temperature:

High fusing: 1300High fusing: 1300 – – 14001400°°C used for theC used for the

manufacture of denture teethmanufacture of denture teeth Low fusing: 850Low fusing: 850 – – 11001100°°C, used for most dentalC, used for most dental

restorations.restorations.

Classification based on esthetic role of porcelain:

a. Opaque porcelain

b. Body porcelain (incisal or enamel; gingival ordentin; modifier)

c. Stains or glazes



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Compaction, firing, glazingCompaction, firing, glazing

1.1. Compaction: Porcelain powder + distilledCompaction: Porcelain powder + distilled

water compacted onto a platinum foil. water compacted onto a platinum foil.

2.2. Firing: done under vacuum in a furnace.Firing: done under vacuum in a furnace.

Shrinkage may occur as particles fuseShrinkage may occur as particles fuse(compensation), Cooling should be slow (compensation), Cooling should be slow



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Continue,Continue,

3.3. Glazing: to improveGlazing: to improve

appearance and removeappearance and removesurface imperfectionssurface imperfections

such as porosities.such as porosities.



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PropertiesProperties

BrittlenessBrittleness Low tensile, high compressive.Low tensile, high compressive.

Cracks travel from inner to outerCracks travel from inner to outer

surfacesurface Thermal conductivity Thermal conductivity Low. Good thermal insulatorLow. Good thermal insulator

HardnessHardness >human enamel, can cause wear of >human enamel, can cause wear of natural teethnatural teeth

Static fatigueStatic fatigue Time dependent decrease in strength Time dependent decrease in strength

due to hydrolysis of Sidue to hydrolysis of Si--O inO in

porcelain structureporcelain structure



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PropertiesProperties

Fracture in ceramics occur through crack Fracture in ceramics occur through crack

propagation, especially when placed underpropagation, especially when placed undertension. How to improve strength and preventtension. How to improve strength and prevent

crack propagation:crack propagation:

By generating compressive stresses in these areas.By generating compressive stresses in these areas.

How?How?

Ion strengthening (using salt paste)Ion strengthening (using salt paste) Thermal strengthening Thermal strengthening



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Porcelain shadePorcelain shade

Metal oxides are added to create different shadesMetal oxides are added to create different shades

The lab. Technician selects the porcelain powder according to The lab. Technician selects the porcelain powder according to

shade selected by dentistshade selected by dentist

Each powder is mixed with distilled water to form a pasteEach powder is mixed with distilled water to form a paste



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Alumina inserts and aluminous Alumina inserts and aluminous

porcelain porcelain Methods used to strengthen porcelain andMethods used to strengthen porcelain and

prevent crack propagation:prevent crack propagation: Use an alumina core, on which crown is constructedUse an alumina core, on which crown is constructed

Pure alumina inserts in the form of sheets placedPure alumina inserts in the form of sheets placed

palatally (itpalatally (it’’s opaque)s opaque)

Adding powdered alumina to porcelain. Alumina Adding powdered alumina to porcelain. Alumina

particles act as crack stoppersparticles act as crack stoppers



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Crack stoppers.Crack stoppers.



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Sintered alumina core ceramicsSintered alumina core ceramics

InceramInceram

Duplicate die is made fromDuplicate die is made from

special plasterspecial plaster

Mixture from alumina powderMixture from alumina powder

and water is painted on the dieand water is painted on the die

(alumina slip). Thickness 0.5mm(alumina slip). Thickness 0.5mm

Sintering for 2 hours at 1120Sintering for 2 hours at 1120 °°CC



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Continue,Continue,

Slurry of lanthanumSlurry of lanthanumaluminosilicate glass isaluminosilicate glass is

painted on the slip andpainted on the slip andfired at 1100fired at 1100 °°C to fillC to fill voids between alumina voids between aluminaparticles.particles.

Microblasting to removeMicroblasting to removeexcess then refiring 960excess then refiring 960°°CC

Dentine and enamelDentine and enamelporcelain layers are addedporcelain layers are addedas usualas usual



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InIn--CeramCeram

Alumina, 400 Alumina, 400--500 MPa500 MPa

flexural strengthflexural strength



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Continue,Continue,

Spinell, MgAlSpinell, MgAl22OO44 , offers, offers

better esthetic thanbetter esthetic thanalumina but a slightly alumina but a slightly

lower flexural strength.lower flexural strength.

recommended for inlaysrecommended for inlays(350 MPa flexural(350 MPa flexural

strength)strength)



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Continue,Continue,

Zirconia, based on inZirconia, based on in--

ceram alumina with 33%ceram alumina with 33%Zirconia (800 MPaZirconia (800 MPa

flexural strength)flexural strength)



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Injection moulded and pressedInjection moulded and pressed

ceramicsceramics Early system:Early system:

Cerestore. Crown cores were produced by injectionCerestore. Crown cores were produced by injectionmoulding which improved adaptation. Shrinkagemoulding which improved adaptation. Shrinkage

reduced by incorporating magnesium oxide (reactsreduced by incorporating magnesium oxide (reacts

with alumina expansion with alumina expansion

Technique: Technique:

Crowns made through using a wax pattern on an epoxy Crowns made through using a wax pattern on an epoxy

resin die. Aluminous porcelain is injected under pressureresin die. Aluminous porcelain is injected under pressure

then fired at 1300then fired at 1300 °°C. veneers of porcelain are added forC. veneers of porcelain are added for

appearanceappearance



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Continue,Continue,

Empress systems:Empress systems:

Empress I: Based on LeuciteEmpress I: Based on Leucite--reinforced feldsparreinforced feldsparglass ceramics. Constructed in a manner similar toglass ceramics. Constructed in a manner similar to

the lost wax technique. The porcelain is injectedthe lost wax technique. The porcelain is injected

under pressure.under pressure. Empress II: based on lithium Disilicate & ApatiteEmpress II: based on lithium Disilicate & Apatite

glass ceramics. Flexural strength 300glass ceramics. Flexural strength 300--400 MPa.400 MPa.

Recommended for 3 unit bridges and to replaceRecommended for 3 unit bridges and to replace

anterior or premolar teethanterior or premolar teeth



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3.a)3.a) lithiumlithium disilicate and 3.b) apatite glassdisilicate and 3.b) apatite glass--ceramicceramic II

lithium disilicate gc apatite gc

IPS Empress ® 2, IPS Eris ®

II



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2. Leucite glass-ceramics

molding

furnace chamber

pressure unit

pressing plunger(1.8 - 2.0 MPa)

Al2O3 plunger

glass-ceramicingotspecimen

investmentcylinder

II

IPS Empress ®

lost wax technique

mold

C l d l lliC t l d l t lli



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Cast glass and polycrystallineCast glass and polycrystalline

ceramicsceramics Used for making single crownsUsed for making single crowns

Crowns constructed in a manner similar to lost waxCrowns constructed in a manner similar to lost waxtechnique but non metal is involvedtechnique but non metal is involved

Molten ceramic is cast centrifugally into the mould atMolten ceramic is cast centrifugally into the mould at

13501350°°C.C. Transparent glass crown result Transparent glass crown result

Heat treatment (ceramming) at 1075Heat treatment (ceramming) at 1075°°C for 10 hoursC for 10 hours

Color matching is achieved by adding layers of Color matching is achieved by adding layers of porcelain and refiring porcelain and refiring

Further color matching by using proper shade for luting Further color matching by using proper shade for luting agentagent

II Dental glass ceramics as restorative II



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II. Dental glass-ceramics as restorativeBIOMATERIALS

1 2

3

II

glass-ceramic as single units(metal-free)

glass-ceramic on a metal framework

glass-ceramic asmulti-unit bridge

(metal-free)

Computer aided design/computer aidedComputer aided design/computer aided



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Computer aided design/computer aidedComputer aided design/computer aided

manufacturer (CAD/CAM) porcelainmanufacturer (CAD/CAM) porcelain

restorationsrestorations Used to make inlays, onlays, veneersUsed to make inlays, onlays, veneers

An image of the preparation is captured An image of the preparation is captured Restoration is fabricated by a milling machineRestoration is fabricated by a milling machine

Design is done within 10Design is done within 10--25 minutes25 minutes Milling process takes 5Milling process takes 5--10 minutes10 minutes

Try in Try in

Cementation by etching with hydrofluoric acid,Cementation by etching with hydrofluoric acid,silane agent, then cementation with dual curesilane agent, then cementation with dual cure

resinresin



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CAD/CAM disadvantagesCAD/CAM disadvantages

Disadvantages:Disadvantages:

Not as accurate, so the fit may not be as goodNot as accurate, so the fit may not be as good The margins will have greater resin cement lines that The margins will have greater resin cement lines that

may wear down and leak and irritate gingival tissue.may wear down and leak and irritate gingival tissue.

Clinical consideration:Clinical consideration:

Preparation should be smooth and no undercutPreparation should be smooth and no undercut

Surface should be coated with reflective powderSurface should be coated with reflective powder(thin and uniform)(thin and uniform)



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Materials usedMaterials used

Conventional feldspathicConventional feldspathic

porcelainporcelain

Glass ceramicsGlass ceramics

InIn--ceram like porcelainceram like porcelain



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Porcelain fused to metal (PFM)Porcelain fused to metal (PFM)

Combines strength (metal) and estheticsCombines strength (metal) and esthetics

(porcelain).(porcelain). Made form low fusing porcelain that binds toMade form low fusing porcelain that binds to

the metal through an oxide layer covering thethe metal through an oxide layer covering the

metal.metal.

Thickness of metal where it binds to porcelain is Thickness of metal where it binds to porcelain is

0.30.3--0.5 mm0.5 mm



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Continue,Continue,

Materials used are feldspathic porcelainMaterials used are feldspathic porcelain

reinforced with leucite. Leucite:reinforced with leucite. Leucite: Adds strength Adds strength

Increases CTE closer to the metal CTEIncreases CTE closer to the metal CTE

Requirements of the alloy:Requirements of the alloy:

Be able to withstand porcelain firing temperatureBe able to withstand porcelain firing temperature

Rigid enough for porcelain supportRigid enough for porcelain support

Be able to bond with porcelainBe able to bond with porcelain

CTE similar to that of porcelainCTE similar to that of porcelain



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Types of alloys used Types of alloys used

High gold alloys:High gold alloys:

High palladium/platinumHigh palladium/platinum Raises melting temperatureRaises melting temperature

Decrease CTE of metalDecrease CTE of metal

Trace amounts of tin and indium to promote Trace amounts of tin and indium to promotebonding with porcelainbonding with porcelain


Melting range is still low Melting range is still low

Modulus of elasticity is low Modulus of elasticity is low



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Ceramo-metal restorations



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Continue,Continue,

Low Low --gold alloys:gold alloys:

50% gold50% gold 30% palladium30% palladium

10% silver10% silver

10% indium10% indium

Advantages: Advantages:

Cost effectiveCost effective

Higher stiffnessHigher stiffness

Higher melting rangeHigher melting range



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Continue,Continue,

SilverSilver--palladium alloys:palladium alloys:

60% palladium60% palladium 30% silver30% silver

10% indium or tin10% indium or tin

Same advantages as low gold alloysSame advantages as low gold alloys



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Continue,Continue,

NickelNickel--chromium alloys:chromium alloys:

7070--80% nickel80% nickel

1010--25% chromium25% chromium

Molybdenum, tungsten, berylliumMolybdenum, tungsten, beryllium

Bonding is through ceramic oxide layerBonding is through ceramic oxide layer Advantages: high melting range, rigid. Advantages: high melting range, rigid.


High casting shrinkageHigh casting shrinkage

Voids in casting Voids in casting

Lower bond strength to porcelainLower bond strength to porcelain



40PFM construction



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P l i f ilP l i f il



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Porcelain failuresPorcelain failures

Problems related to the chemical bond betweenProblems related to the chemical bond between

metal and porcelain:metal and porcelain: Oxide layer too thick or inadequate cracks nearOxide layer too thick or inadequate cracks near

or at interface cracks propagateor at interface cracks propagate

Fracture of porcelain.Fracture of porcelain.

Incompatibility of CTE between metal andIncompatibility of CTE between metal and

porcelain (porcelain should have slightly lessporcelain (porcelain should have slightly lessthermal expansion to prevent cracking atthermal expansion to prevent cracking at

interface)interface)

P l i iP l i i



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Porcelain repairPorcelain repair

Can be done if fracture is not too expensiveCan be done if fracture is not too expensive

Can be done in vivo with composite:Can be done in vivo with composite: Mentioned in previous lecturesMentioned in previous lectures

All i iAll i i



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All ceramic restorations All ceramic restorations

Mainly used for anterior teeth were esthetics is anMainly used for anterior teeth were esthetics is animportant factor and stress is not high.important factor and stress is not high.

Termed porcelain jackets Termed porcelain jackets

Made from low fusing porcelainMade from low fusing porcelain

New ceramics were fabricated, stronger than olderNew ceramics were fabricated, stronger than olderporcelain, can be used for posterior teeth but fractureporcelain, can be used for posterior teeth but fracturerate was highrate was high

The newer ceramics are less abrasive to natural teeth The newer ceramics are less abrasive to natural teethand easier to finish and polish after adjustmentand easier to finish and polish after adjustment

Materials used were mentioned previously (reinforcedMaterials used were mentioned previously (reinforced

ceramics)ceramics)



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All ceramic crownsAll ceramic crowns



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All ceramic crowns All ceramic crowns

Appear more vital compared to PFM because Appear more vital compared to PFM because

they do not need an opaque layer of porcelain tothey do not need an opaque layer of porcelain to

cove the metal part. Characterized by:cove the metal part. Characterized by: Appear similar to natural teeth because they are Appear similar to natural teeth because they are

fluorescent (they emit light when hit with UV light)fluorescent (they emit light when hit with UV light)

They are opalescent ( because they will have a bluish They are opalescent ( because they will have a bluish

tinge when light reflects on them, and an orangetinge when light reflects on them, and an orange--

yellowish tinge when light passes throughyellowish tinge when light passes through Inceram, aluminous porcelain, EmpressInceram, aluminous porcelain, Empress



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P r l in n rPorcelain veneers



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Porcelain veneersPorcelain veneers

A reduction of 0.5mm from the labial surface is A reduction of 0.5mm from the labial surface is

requiredrequired

Materials used:Materials used:

Feldspathic porcelainFeldspathic porcelain

Glass ceramicsGlass ceramics Pressed ceramicsPressed ceramics

Bonded with resin. Enamel surface and porcelainBonded with resin. Enamel surface and porcelain

surface treatment?surface treatment?

Trial cementation with water soluble cement maybe Trial cementation with water soluble cement maybe

donedone



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Why are ceramic veneers better than Why are ceramic veneers better than



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y

composite veneerscomposite veneers Better estheticsBetter esthetics

Color stability Color stability Better surface finishBetter surface finish

Abrasion resistance is higher Abrasion resistance is higher Better tissue compatibility Better tissue compatibility

CTE similar to that of tooth structureCTE similar to that of tooth structure

Capillary technologyCapillary technology



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Capillary technologyCapillary technology

Used for producing PFM. Procedure:Used for producing PFM. Procedure:

Metal substructure is produced in two stages:Metal substructure is produced in two stages: Wax strip loaded with powdered palladium is adapted to cast Wax strip loaded with powdered palladium is adapted to cast

This is fired to burn of wax and leave a capillary network of This is fired to burn of wax and leave a capillary network of

metalmetal Second strip loaded with gold (95%) is added then fired againSecond strip loaded with gold (95%) is added then fired again

so gold infiltrates the network and forms the metal crownso gold infiltrates the network and forms the metal crown

Porcelain veneers are added for shade (35Porcelain veneers are added for shade (35µµm)m)

Bond between porcelain and metal is mechanicalBond between porcelain and metal is mechanical

Bonded platinum foilBonded platinum foil



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Bonded platinum foilBonded platinum foil

Instead of having a metal substructure, porcelainInstead of having a metal substructure, porcelain will be bonded to platinum foil. will be bonded to platinum foil.

Technique involves laying down two layers of Technique involves laying down two layers of platinum foil.platinum foil.

The outer foil is tin plated to aid in porcelain The outer foil is tin plated to aid in porcelainbonding bonding

The inner foil is removed before cementation The inner foil is removed before cementation This restoration is not as strong as traditional This restoration is not as strong as traditional

PFMPFM



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ReferencesReferences Applied dental materials Applied dental materials

Documents

Lecture 13 & 14 - Ceramics (Slides)