Ceramic2

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CERAMICS

By:DR. BHARTI DUAPG IST YEAR

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CONTENTS 1.INTRODUCTION

2.HISTORY

3.CLASSIFICATION

4.COMPOSITION

5. STRENGTHNING MECHANISM OF CERAMIC

6. PROPERTIES

7. SHADE MATCHING GUIDELINES

8. METAL CERAMIC SYSTEMS

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9.ALL CERAMIC SYSTEM

10.CRITERIA FOR SELECTION AND USE OF DENTAL CERAMICS

11.RECENT ADVANCES IN CERAMIC

12. REFERENCES

13.CONCLUSION

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INTRODUCTION

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DEFINITION1

Ceramics : compounds of one or more metals with a nonmetallic element, usually oxygen. They are formed of chemical and biochemical stable substances that are strong, hard, brittle, and inert nonconductors of thermal and electrical energy1 – G.P.T-8

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PORCELAIN1

A ceramic material formed of infusible elements joined by lower fusing materials. Most dental porcelains are glasses and are used in the fabrication of teeth for dentures, pontics and facings, metal ceramic restorations including fixed dental prostheses, as well as all-ceramic restorations such as crowns, laminate veneers, inlays, onlays, and other restorations.G.P.T-8

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HISTORY

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HISTORY2,3,4

Historically, three basic types of ceramic materials were developed;

Earthernware, Stoneware, & Whiteware.

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In 700 B.C. the Etruscans made teeth of ivory and bone that were held in place by a gold framework.

By the 10th century A.D, ceramic technology in China had advanced to a highly sophisticated stage.

As trade with the far east grew, this infinitely superior material came to Europe from China, during the 17th century.

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HISTORY

In 1717, a Jesuit missionary Father d’Entrecolles leaked the secret of Chinese porcelain and passed it on to M. de Reamer

1728 – Pierre Fauchard, a French dentist first proposed the use of porcelain in dentistry.

By 1825- Samuel Stockton began fabrication of fused porcelain teeth in Philadelphia.

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HISTORY

A significant improvement in the fracture resistance of porcelain crowns was reported by Mc1ean and Hughes in 1965 when a dental aluminous core ceramic was used.

1983-84 – the first castable glass ceramic was introduced by Grossman and Adair called DICOR

1985 – CAD/CAM technique was developed by Mormann and Brandestini

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The future of dental ceramics is bright

because the increased demand for tooth-

colored restorations will lead to an increased

demand for ceramic- based restorations.

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CLASSIFICATION

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CLASSIFICATION OF DENTAL CERAMICS2

According to use: Anterior bridges Posterior bridges Crowns Veneers Post and cores FPDs Stain ceramic Glaze ceramic

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According to composition: Pure alumina Pure zirconia Silica glass Leucite-based glass ceramic Lithia-based glass ceramic

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According to processing methods: Sintering Casting machining

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According to translucency: Opaque porcelain

Dentin porcelain

Enamel porcelain

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Acccording to firing temperature.3,5

1. High-fusing: 1,290 to 1,370°C 2. Medium-fusing: 1,090 to 1,2600C 3. Low-fusing: 870 to 1,065oC OR2

1. High fusing 13000C2. Medium fusing 1101-1300oC3. Low fusing 850-11000C4. Ultra-low fusing - <8500C

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STRUCTURE AND COMPOSITION

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STRUCTURE AND COMPOSITION

Porcelain :

Refer to specific range of ceramic materials made by

mixing

kaolin quartz feldspar

COMPOSITION OF FELDSPATHIC PORCELAIN2,3,5

1. Feldspar - 60 to 80% - Basic glass

former

2. Kaolin - 3 to 5% - binder

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3. Quartz - 15 to 25% - Filler

4.Oxides of Na, K,Ca - 9 to 15% -Fluxes

(glass

modifiers)

7. Alumina - 8 to 20% - Glass former and

flux

8. Metallic pigments - <1% - Color matching

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Ferric oxide, platinum Grey.

Chromium oxide, copper oxide Green

Cobalt salts Blue

Ferrous oxide,nickel oxide Brown

Titanium oxide Yellowish brown

Manganese oxide Lavender

Chromium tin, Chromium alumina Pink

Indium Yellow, ivory

9.Opacifying agents

The common metallic oxides used are –

• Cerium oxide,

• Titanium oxide,

• Tin oxide, and

•Zirconium oxide (ZrO2)

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The typical high-fusing porcelain is composed of

feldspar (70% to 90%), quartz (11% to18%), kaolin (1% to 10%)

Medium fusing porcelain has 64.2% silicon dioxide

19% aluminium oxide

Low fusing porcelain has 69.4% silicon dioxide 8% aluminium

oxide

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STRENGTHENING MECHANISM

OF CERAMICS 2

( Development of residual

compressive stress) Ion exchange Thermal tempering. Thermal compatibility

And

( Interruption of crack propagation )Dispersion of crack propagationDispersion of crystalline phase

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Ion Exchange

The ion-exchange process is sometimes called chemical tempering.

When a sodium containing glass article is placed in a bath of molten potassium nitrate, potassium ions in the bath exchange places with some of the sodium ions in the surface of the glass article and remain in place after cooling.

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THERMAL TEMPERING It is done by rapidly cooling (quenching) the

surface of the object while it is hot and in the softened (molten) state.

As the molten core solidifies, it tends to shrink, but the outer skin remains rigid.

The pull of the solidifying molten core, as it shrinks, creates residual tensile stresses in the core and residual compressive stresses within the outer surface.

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THERMAL COMPATIBILITY

Ideally the porcelain should be under slight compression in the final restoration.

Select an alloy that contracts slightly more than the porcelain on cooling to room temperature.

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DISPERSION OF CRACK PROPAGATION

Ceramic can be reinforced with a dispersed phase of a different material that is capable of hindering a crack from propagating through the material.

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DISPERSION OF CRYSTALLINE PHASE

When a tough , crystalline material is added to glass, the glass is toughned and strengthened because the crack can not penetrate the added crystalline particle.

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PROPERTIES

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STRENGTH3

Alumina based ceramic

Flexural Strength-139 MPa

Shear Strength -145 MPa

Leucite-reinforced feldspathic porcelain

Flexural Strength-104 MPa

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ABRASION RESISTANCE2

Natural tooth - 343 KHN Porcelain 460 – KHN

Hence , it causes wearing of natural tooth and metal restorations

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Enamel wear by ceramics may adversely affect

maintenance of the vertical dimension of occlusion

and can increase the potential for thermal sensitivity.

Based on the literature, it can be concluded that

material factors, their proper handling, and control of

the patient's intrinsic risk factors related to wear are

critically important for the reduction of enamel wear

by dental ceramics. 

Oh WS, Delong R, Anusavice KJ.Factors

affecting enamel and ceramic wear: A literature

review.J Prosthet Dent 2002 Apr;87(4):451-9

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SHRINKAGE3

  Volumetric shrinkage – 28-37% - low fusing porcelain

28-34% - high fusing porcelain

Linear shrinkage - 14 % - low fusing porcelain

11.5%- high fusing porcelain

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COEFFICIENT OF THERMAL EXPANSION (CTE)3

CTE should match tooth structure to minimize shrinkage .

CTE should be slightly lower than that of the casting alloy keeping the porcelain in residual compression upon cooling from firing temperatures.

CTE: 12-13X 10-6/oC

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Properties necessary for use of ceramics in the fabrication of dental

restorations5

1. Low fusing temperature

2. High viscosity

3. Resistance to devitrification

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COLOUR STABILITY

Ceramics are the most stable tooth coloured materials .

The metallic oxides used as colorants do not undergo any change in shade after firing is complete .

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SHADE MATCHING GUIDELINES 2,4

Three factors upon which color is dependent:

(1)the observer,

(2) the object,

(3) the light source.

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The selection of tooth or restorative shades should be done at the start of a clinical session before the operator’s eyes become fatigued.

Have the patient remove lipstick, heavy makeup or large

jewelry that may influence the color perception.

Do not use operatory light for shade selection.

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Ideally the clinician should use illumination of northern

light from a blue sky.

Sunlight near the window can be used.

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CRISTOPHER CK.SHADE SELECTION.AUST DENT PRAC. 2007;116-119

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Hold the appropriate shade tab near the tooth to be restored ,

party covered with the patient’s lip.

Shade selection should be done quickly within 30 seconds

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Try to select the basic hue of the tooth by matching the

shade of the patient’s canine, usually the most highly

chromatic tooth in the mouth.

With the correct hue group selected, work within the

group on the shade guide to obtain the proper match.

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Another factor that is important to the aesthetic

qualities is the cementing medium.

For example, an opaque material such as zinc

phosphate cement, can change the shade of a

translucent crown because of its light absorption and

its color.

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CRISTOPHER CK.SHADE SELECTION.AUST DENT PRAC. 2007;116-119

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DENTAL CERAMICS:

METAL CERAMICS ALL CERAMIC

METAL CERAMICS

Mechanical properties Esthetic properties

Metal Ceramic

REQUIREMENTS FOR A METAL-CERAMIC SYSTEM 2

High fusing temperature of the alloy.

Low fusing temperature of the ceramic.(difference should not be more than 100oC.)

The ceramic must wet the alloy readily .

Adequate stiffness and strength of alloy core.

An accurate casting metal coping is required. Adequate design of restoration is critical.

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REQUIREMENTS2

Ceramic must have coefficient of thermal contraction closely matching to that of alloys.

The optimum difference between the two should not be greater than 1 x 10-6/°C.

Metal oxide is necessary to promote bonding .

High melting ranges for gold alloys are necessary to prevent sag, creep, or melting of the coping during porcelain firing cycle.

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METAL CERAMIC ALLOYS

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BONDING PORCELAIN TO METAL2

Success of a metal ceramic restoration is the development of a durable bond between the porcelain and the alloy.

Mechanical interlocking

Chemical bonding

Theories of metal

ceramic bonding :

Bond failure classification: O’Brien

Type I: Metal porcelain:

• When the metal surface is totally depleted of oxide prior to firing porcelain, or

• When no oxides are available• Also on contaminated porous surface.

Type II: Metal oxide- porcelain: • Base metal alloy system.• The porcelain fractures at the metal oxide surface

leaving the oxide firmly attached to the metal.

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Type III: Cohesive within porcelain:• Tensile fracture within the porcelain when

the bond strength exceeds the strength of the porcelain.

Type IV: Metal- metal oxide:

• Base metal alloys • Due to the overproduction of Ni and Cr

oxides• The metal oxide is left attached to ceramic.

5.Type V: Metal oxide- Metal oxide

•Fracture occurs through the metal because of the overproduction of oxide causing a sandwich between porcelain and metal

6. Type VI :Cohesive within metal

• Unlikely in individual metal ceramic crowns.

• Connector area of bridges.

FABRICATION OF A METAL CERAMIC RESTORATION2,3,4

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METAL PREPARATION 4 –

Sharp angles or pits on the veneering surface of metal-ceramic restoration should be avoided .

Convex surfaces and rounded contours should be created so that the porcelain is supported without development of stress concentration.

The intended metal-ceramic junction should be as definite ( 90 0 ) and as smooth as possible.

The metal framework should be sufficiently thick to prevent distortion during firing.( min 0.3 mm for noble metals & 0.2 mm for base metals)

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Metal Preparation

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OXID IZ ING

To establish a chemical bond between metal and porcelain , a controlled oxide layer must be created on the metal surface. The oxide layer is obtained by placing the substructure on a firing tray , inserting it into the muffle of a porcelain furnace and raising the temperature to a specified level that exceeds the firing temperature of porcelain.

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CONDENSATION

The process of packing the powder particles together and removing excess water is known as condensation.

During this step , the porcelain powder is mixed with distilled water or any other liquid binder and applied on the metal substrate in subsequent layers.

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METHODS OF CONDENSATION

VIBRATION Method

SPATULATION Method

BRUSH Method

ULTRASONIC Method

GRAVITATIONAL Method

WHIPPING Method

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CERAMOSONIC CONDENSERULTRASONIC CONDENSING UNIT FOR PORCELAIN BUILD-UP

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Condensing porcelain 1. Build up porcelain using a brush or spatula

and set the tweezers against the vibrating platform intermittently. Remove the moisture leaking up out of the porcelain with a tissue paper.

CONDENSATION

Opaque porcelain application

Opaque porcelain is applied first to mask the metal, to give the restoration its basic shade, and to initiate the porcelain-metal bond.

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No attempt should be made to thoroughly mask the metal

with this initial application.

It is intended to completely wet the metal and penetrate

the striations created by finishing.

The coping is dried and fired under vacuum

The second application of opaque porcelain should mask

the metal .

The powder and liquid are mixed to a creamy consistency

and applied to the coping with a brush in a vibrating

motion.

opaque porcelain is condensed to a thickness of O.3mm

and fired. 66

Dentin and Enamel Porcelain Application

Mix dentin porcelain to a creamy consistency with distilled water or the manufacturer's recommended liquid.

Then apply it over the opaque with a sable brush or small spatula, starting at the gingivofacial of the coping, which is seated on the working cast.

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First develop the full contour of the crown in dentin porcelain with a brush. Vibrate the porcelain to condense it, absorbing the liquid with tissue.

The completed buildup should be over contoured .

When the porcelain is condensed and dried to a consistency of wet sand, carve the dentin back to allow the placement of the enamel porcelain.

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Apply the enamel porcelain to restore the full contour of the restoration.

When completed, the restoration should be slightly larger incisally to compensate for the shrinkage .

Overall, make the crown about one-fifth larger than the desired size to compensate for the 20% shrinkage that will occur during firing .

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FIRING

Firing is carried out for fusing (sintering) the porcelain.

The compacted mass is placed on a fire clay tray and inserted into the muffle of the ceramic or porcelain furnace.

PREHEATING It is first placed in front of the muffle of a preheated furnace and later

inserted into the furnace(5 min)

If placed directly into the furnace, the rapid formation of steam can break up the condensed mass.

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TYPES OF FIRING

AIR FIRING

VACCUM FIRING

GAS FIRING

HOW VACUUM FIRING REDUCES POROSITY 2 –

When the porcelain is placed in the furnace , the powder particles are packed together with air currents around them.

As the air pressure inside the furnace muffle is reduced to about one-tenth of atmosphere pressure by vacuum pump, the air around the particles is also reduced to this pressure.

As the temperature rises, the particles sinter together, and closed voids are formed within the porcelain mass.

The air inside these closed voids is isolated from furnace atmosphere.

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At a temperature of about 55OC, below the upper firing temperature, the vacuum is released and the pressure inside the furnace increases a factor of 10, from 0.1 to 1 atm.

Because the pressure is increased by a factor of 10, the voids are compressed to one-tenth of their original size, and the total volume of porosity is accordingly reduced.

Not all air can be evacuated from the furnace , therefore a few bubbles are present in vacuum sintered porcelains, but they are markedly smaller than the ones obtained by air firing.

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TEMPERATURE TIME

OXIDATION 9300C 15 MIN

BASE PASTE 960OC 19 MIN

SHADE PASTE 975OC 16 MIN

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TEMPERATURE TIME

DENTINE 9350C 19 MIN

ENAMEL 935OC 19 MIN

GLAZE 930OC 11 MIN

COOLING

Too rapid cooling of outer layers may result surface crazing or cracking; this is also called thermal shock.

Slow cooling is preferred, and is accomplished by gradual opening of the porcelain furnace.

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PORCELAIN SURFACE TREATMENT 5

Once the desired contours and occlusion have been achieved, the restoration must receive a surface treatment i.e glazing

GLAZING -

After firing, Porcelains are glazed to a glossy surface.

It enhances strength, esthetics and hygiene. Glazed porcelain is much stronger than unglazed. The glaze is also effective in reducing crack

propagation.

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TYPES OF GLAZE –

1. Self glaze Porcelains can be self glazed by heating under

controlled condition, i.e. it is heated to its fusion temperature and maintained for 5 minutes.

it causes only the surface layer to fuse and flow over the surface to form a vitreous layer called glaze.

Chemical durability of self glaze is better than over-glaze.

2. Over glaze The glaze powder is mixed with liquid, applied over

the smoothened crown and fired at temperature lower than that of body.

But it should be avoided because it gives - Unnatural appearance Loss of contour and shade modification  

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79ALL CERAMIC SYSTEM

Classification of all ceramic systems.

GLASS CERAMICS

SLIP CASTING CERAMICS

HOT PRESSED/INJECTION MOLDED

SINTERED CERAMICS

MACHINABLE CERAMICS

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CASTABLE/ GLASS CERAMICS

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Glass Ceramics.

Mica based: Dicor

Hydroxyapatite based: Cerapearl

Lithia based: Experimental.

These ceramics are supplied as ceramic ingots which are used to fabricate the restoration using a lost wax and centrifugal casting technique.

DICOR was the first commercially available castable ceramic material for dental use.

This has a glassy matrix and a crystalline phase.

Glass ceramic: Is a ceramic consisting of a glass matrix phase and at least one crystal phase that is produced by the controlled crystallization of the glass.

MICA BASED GLASS CERAMICS

DICOR

Developed by The Corning works and

marketed by the Dentsply.

International Term DICOR is the combination

of the manufacturer's names.

DICOR is a castable polycrystalline fluoride

containing tetrasilic mica glass ceramic

material, initially cast by lost wax technique

and subsequently heat treated resulting in a

controlled crystallization to produce a glass

ceramic material.

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COMPOSITION

SiO2-45-70%

K2O- 20%

MgO- 13-30%

55% vol of tetrasilicic flourmica crystals

increased strength and toughness

increased resistance to abrasion

thermal shock resistance

chemical durability

decreased translucency

Supplied as –

DICOR castable ceramic cartridges

Special DICOR casting crucibles each contain a 4.1 gm

DICOR ingot

and DICOR shading porcelain kit.

EQUIPMENT REQUIRED –

1. DICOR Casting machine

2. DICOR Ceramming furnace with ceramming Trays.

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FABRICATION OF CASTABLE CERAMICS RESTORATION CONSISTS OF MAINLY 2 STEPS –

1. CASTING –

The glass liquefies at 13700C to such a degree that

it can be cast into a mold using lost-wax and

centrifugal casting techniques.

The wax pattern of the proposed restoration made

on the model/die is invested in Castable ceramic

investment in a double line casting ring and

burned out in a conventional burnout at 9000C for

30 minutes. 87

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Glass ingots of castable ceramic material

is placed in a special zirconia crucible and

centrifugally cast in a electronically

controlled DICOR casting machine

maintaining the spin pressure for upto 4

minutes and 30 seconds.

Transparent glass casting obtained is

amorphous and fragile.

2.CERAMMING –

The cast glass material is subjected to a single

–step heat treatment called as “Ceramming”

to produce controlled crystallization by

internal nucleation and crystal growth of

microscopic plate like mica crystals within

glass matrix.

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METHOD –

Transparent casting is embedded in castable ceramic embedment material ( gypsum-based ) and placed in a Ceramming tray in the DICOR Ceramming furnace.

CERAMMING CYCLE –

6500C-10750C for 1.5 hrs and sustained upto 6 hours.

Difference between Dicor and Dicor MGC(machinable glass ceramic)

Dicor Dicor MGC

55%vol of tetrasilicic fluoramica crystals.

70% vol of tetrasilicic flouramica crystals which are 2 µm in diameter

Crystallization done by the technician.

Higher quality product that is crystallized by the manufacturer and provided as cadcam blanks or ingots.

Mechanical properties similar.

Less translucent than Dicor.

1) Uniformity and purity of the material.

3) Minimal processing shrinkage.

4) Good fit.

5) Low CTE equal to that of the tooth structure.

6) Minimal abrasiveness to the tooth structure.

7) Radio opacity like dentin.

8)Moderately high flexural strength.(152 MPa)

Advantages of Dicor:

Disadvantages of DICOR• OPAQUE due to the presence of mica:

Chamaleon effect the transparent crystals scatter the incoming light.

The light and also its color, is distributed as if the light is bouncing off a large number of small mirrors that reflect the light and spread it over the entire glass-ceramic.this property is called CHAMALEON effect.

•Low tensile strength.

•Inability to be colored internally

•Labour intensive

•High cost

Inlays, Onlays ,partial tooth coverage

Indications

HYDEROXYAPETITE BASED CASTABLE

GLASS CERAMICS : Cerapearl

COMPOSITION CaO- 45% P2O5- 15% Mg2O- 5% SiO2- 35%

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PROPERTIES OF CERAPEARL –

CASTING SHRINKAGE is 0.53% COEFFIECIENT OF THERMAL EXPANSION is 11.0

X 10-6/0C Melts at 14600C and flows like a melting glass.

The cast material has an amorphous microstructure when reheated at 8700C forms crystalline Hydroxyapetite.

Biocompatible: Crystalline structure similar to enamel.

Modulus of rupture :150 Mpa.

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S

SINTERED ALL-CERAMIC

MATERIALS2,3

SINTERED CERAMICS Leucite- reinforced feldspathic porcelain: Optec HSP

Aluminous based porcelain( Pt foil): Vitadur- N TM core

Alumina based porcelain: Hi ceram

Magnesia based feldspathic porcelain( Experimental)

Zirconia based porcelain: Mirage II

Hydrothermal low fusing Ceramics: Duceram LFC.

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SINTERED ALL-CERAMIC MATERIALS2,3

Supplied as powders which can be mixed with water to form a slurry.

This slurry can be built up in layers on a refactory die to form the restoration.

The powders are avaliable in different shades and translucencies.

These sintered ceramics are thus similar to the conventional feldspathic porcelains in their method of fabrication.

However they are stronger as they are reinforced by crystalline phases.

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Alumina-Based Ceramic

Mclean and hughes (1965) developed Alumina reinforced porcelain core materials

ALUMINOUS CORE CERAMICS

They advocated using aluminous porcelain, which is

composed of aluminum oxide (alumina) crystals

dispersed in a glassy matrix.

The technique devised by McLean used an opaque inner

core containing 50% by weight alumina for high

strength.

This core was veneered by a combination of esthetic

body and enamel porcelains with 15% and 5%

crystalline alumina, respectively and matched thermal

expansion.100

The resulting restorations were approximately

40% stronger than those using traditional

feldspathic porcelain. Why Alumina?

Good Mechanical properties. Interfacial region between alumina and porcelain

virtually stress free. Crystals rather than fine powdered alumina

used. High modulus of elasticity( 350 Gpa) High fracture toughness( 3.5 to 4 Mpa). Significant strengthening of the core.

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Advantages of aluminous porcelains: Increased flexural strength, Increased elasticity and toughness.

Disadvantages of Aluminous porcelain

Extensive reduction, dentin preparation. Bonding is limited. High failure rates.

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LEUCITE REINFORCED FELDSPATHIC PORCELAIN

In this type , the leucite crystals ( Potassium

aluminium Silicate) are dispersed in a glass matrix.

The leucite and glass components are fused together

during baking process at 10200C.

Leucite concentration 50 % wt.

Eg .Optec HSP( Jeneric/ Pentron)

Higher modulus of rupture and compressive strength.

Does not require core unlike aluminous PJC.

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Lack of metal or opaque substructure, Good translucency compared to alumina crowns.Moderate flexural strength( 146 Mpa), Ability to be used without special laboratory equipment.Can be etched.

Advantages:

Disadvantages:

Marginal inaccuracy caused by sintering shrinkage.Potential to fracture in posterior teeth.Increased leucite content :relatively high invitro wear of opposing teeth.Requires a special die material.

Uses: Inlays, onlays, crowns for low stress areas and veneers

•High expansion core material.•CTE :magnesia 13.5 x10-6/0C.

Dispersion strengthening by the magnesia crystals in a vitreous matrix.

Crystallization within the matrix.( Precipitation of fosterite crystals.)

Magnesia based core ceramic 6

Strengthening:

Magnesia based core porcelain 6

Advantages

High CTE: Same body and enamel porcelains used for PFM crowns can be used for all ceramic

Flexural strength of magnesia core :131 MpaTwice as high as feldspathic porcelain( 65 Mpa).

Esthetics superior to PFM.

Disadvantages

Not used for fixed partial dentures.

Mirage II( Myron International, Kansas City). Tetragonal Zirconia fibers

Zirconia based feldspathic porcelains ( Sintered) 6

Advantages –

•Fracture toughness

•Thermal shock resistance

Disadvantages:

Properties such as translucency and fusion

temperature can be adversely affected.

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Alumina based( In- Ceram)In – Ceram SpinellIn – Ceram ZirconiaIn- Ceram 2000.

Slip Cast Ceramics

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SLIP CAST ALL CERAMIC MATERIALS2

Slip-casting involves the condensation of an aqueous porcelain slip on a refractory die. The porosity of the refractory die helps condensation by absorbing the water from the slip by capillary action.

SLIP CASTING _

Is a process used to form “green” ceramic shapes

by applying a slurry of ceramic particles and water

or a special liquid to form a porous substrate( such

as die material), thereby allowing capillary action

to remove water and densify the mass of deposited

particles.

Green state – refers to an as- pressed condition before sintering.

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The starting media in slip-casting is a slip that is an

aqueous suspension of fine alumina particles in water

with dispersing agents.

The slip is applied onto a porous refractory die, which

absorbs the water from the slip and leads to the

condensation of the slip on the die.

The piece is then fired at high temperature (1150° C).

The refractory die shrinks more than the condensed

slip, which allows easy separation after firing. 112

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The fired porous core is later glass-infiltrated,

a unique process in which molten glass is

drawn into the pores by capillary action at

high temperature.

Materials processed by slip-casting tend to

exhibit lower porosity and less processing

defects than traditionally sintered ceramic

materials.

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In ceram is provided as one of the three core ceramics

In-ceram spinel (ICS) In-ceram alumina(ICA) In-ceram zirconia (ICZ)

Core of ICS- MgAl2O4

Core of ICA- 70wt% alumina infiltrated with 30wt% sodium lanthanum glass

Core of ICZ- 70wt% alumina and 30wt% zirconia.

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INDICATIONS2

ICS-anterior single unit inlays, onlays, crowns and veneers

ICA-anterior and posterior crowns and anterior three unit FPD’s

ICZ-posterior crowns and posterior FPD’s

LABORATORY PROCEDURE

In-Ceram – is based on slip-casting of an alumina core with its subsequent glass infusion.

An impression of the master cast preparations is made with an elastomeric impression material.

A special gypsum supplied with In-Ceram is then poured into the impression to produce the die onto which In-Ceram alumina is applied.

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Alumina powder(38 g) is mixed with 5ml of

deionized water supply.

One drop of a dispersing agent is added to help

create a homogenous mixture of alumina in the

water.

one-half of the alumina is added to a beaker

containing the water/dispersant and then

sonicated for 3 minutes in a vitasonic.

This initiated the Dispersion process.

A second quantity of powder equal to one-half of

the remaining amount is then added to the beaker

and sonicated again for 3 minutes.

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The remaining powder may be added and

sonicated for 7 minutes , during the last minute, a

vacuum is applied to remove air bubbles – this

solution of alumina is referred to as “ SLIP” ,which

is then painted onto the gypsum die with a brush.

The alumina core is then placed in the furnace and

sintered using program 1 – slow heating of approx

2OC/min to 120OC to remove water and the binding

agent.

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Second stage of sintering involves a temperature rise of approx 20OC/min to 1120OC for 2 hours to produce approximation of particles with minimal shrinkage of the alumina.

Advantages of the glass infiltrated systems:

High flexural strength and fracture toughness.In-ceram alumina(ICA); STRENGTH- 600 MPa ,TOUGHNESS- 6

In-ceram zirconia (ICZ); STRENGTH-900 MPa , TOUGHNESS-9

Esthetics.

Biocompatibility.

Ability to be used with conventional luting cements.

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Disadvantages of glass infiltrated systems.

High chemical solubility > 1000micro

gms/cm2

Technique sensitive

High cost.

Long time period for fabrication(15-16 hrs

for single crown)

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Contraindication –

If functionally appropriate design of the

restoration is not ensured:

Inadequate preparation

Bruxism.

Severe discoloration of prepared teeth.

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Leucite based: IPS EmpressSpinel based: Alceram

Hot pressed, injection molded

HOT-PRESSED CERAMICS (Leucite based) –

IPS Empress and Optec OPC.

Hot-pressed ceramics are becoming increasingly popular in dentistry.

The restorations are waxed, invested, and pressed in a manner somewhat similar to gold casting.

Marginal adaptation seems to be better with hot-pressing than with the high-strength alumina core materials.

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Most hot-pressed materials contain leucite as a major crystalline phase, dispersed in a glassy matrix.

The crystal size varies from 3 to 10 µm, leucite content is 35% Glass65%

Leucite is used as a reinforcing phase due to the tangential stresses it creates within the porcelain.

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IPS Empress 6

Uses a leucite (40 – 50 %) reinforced feldspathic porcelain.

LEUCITE CRYSTALS ARE USED BECAUSE – they improve fracture toughness & strength.

Conventional lost wax technique is used ,except that it uses special investment and a prolonged burn out cycle.

Lack of metal.Translucent ceramic core Moderately high flexural strengthExcellent fit Excellent esthetics.( Translucence,

flouroscence and opalescence)Minimal shrinkage:

Only shrinkage that occurs is during cooling, that can be controlled with an investment having an appropriate expansion.

Advantages:

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Potential to fracture in the posterior areas.Need to use resin cement to bond the crown micromechanically to the tooth structure.Expensive equipment.

DISADVANTAGES

LABORATORY PROCEDURE

FOR IPS EMPRESS 6

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1. DIE PREPARATION The Cergo die spacer

(one layer of approximately 15 μm in

thickness) or the colored die spacer (two layers of approximately 15 μm in thickness) is used as a placeholder for the cementing gap. In the case of crowns, a special spacer fluid is applied to within 1 mm of the preparation margin on the die.

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2. WAX MODELING Use only wax materials

that burn out without residue.

Use Isolit isolating liquid. For anterior teeth, the

wall thickness of the wax model must be at least 0.7mm.

Thickness of the framework should be more than 50% of the thickness of the veneer in the case of pressable ceramics

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3. SPRUEING

The wax models are sprued with wax sprues (5– 6 mm long for the Cergo press ceramic furnace, 2 – 3 mm for the Multimat Touch&Press). For smaller inlays and copings, the recommended sprue diameter is 3.0 mm, while it is 3.5 mm for more voluminous restorations.

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4. INVESTING TECHNIQUE

Place the muffle ring on the muffle former.

Mix the investment material (Cergo fit or Cergo fit SPEED) as per the manufacturer’s instruction. Vibrate lightly into the muffle, avoiding bubble formation, until all objects are completely covered with investment. Top off the muffle without vibrating.

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5. PRE-HEATING

When using Cergo fit SPEED investment, you may place the muffle directly into the oven pre-heated to 850 ºC after a setting period of 15 minutes.

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6. PRESSING

Maximum of 2 ingots can be used.If wax weight is less than 0.6 gms---- use one

ingotIf wax weight is 0.61gm-1.4gms------ use two

ingots

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BURNOUT PROCEDURE

After the investment has set for 15 to 20 min

place the ring in 8500C

45 min for small ring

60 min for large ring

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7. DIVESTING Make a deep cut into the

investment compound, preferably using a diamond-covered and sintered large carbide disc or(less costly) a carbide disc for metal castings.

Separate the part of the muffle containing the alumina pressing die from the rest of the muffle using a plaster knife or, preferably, by turning in opposite directions.

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7. DIVESTING Use a jet polisher (50 μm, 4

bar) or glass beads to remove the investment all the way to the pressed objects.

Once the objects have become visible, continue abrading across the area using reduced pressure (2 bar).

Clean the alumina pressing die using alumina abrasive and rinse.

Do not use alumina for air-abrading. Do not concentrate the air-abrading force on small areas.

Lithium Silicate based 6

IPS Empress 2 is a recently introduced hot-pressed

ceramic.

The major crystalline phase of the core material is a

lithium disilicate.( 85%)

The material is pressed at 920° C (1690° F) and layered

with a glass containing some dispersed apatite crystals .

The initial results from clinical trials seem quite

promising and may have application for anterior three-

unit fixed partial dentures.

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Property IPS Empress IPS Empress II

Flexural strength 112±10Mpa 400±40

Fracture toughness MPa/ m1/2

1.3±0.1 3.3±0.3

Thermal Expansion coefficient(ppm/0C)

15±0.25 10.6±0.25

Veneering temperature

9100C 8000C

Chemical durability(μg/ cm2

100-200 50

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COMERCIALLY AVAILABLE CAD-CAM SYSTEMS –

Procera

Celay

Sopha’

Cicero

Cerac

Dux

Denticard

The japanese system

The dens system (CERCON)

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CEREC SYSTEM –

1988: CEREC 1( Brains, Zurich, Switzerland) 1994: CEREC 2( Siemens, Benshelm,

Germany) 2000: CEREC 3( Sirona, Bensheim,

Germany) CEREC 3D

The equipment consists of a computer integrated imaging and milling system, with the restorations designed on the computer screen.

At least three materials can be used with this system:

Cerac Vitablocs mark 1

Cerac vitablocs mark 2

Dicor MGC147

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CERAC system consists of – 1. A 3D video camera 2.An electronic image processor with memory

unit 3.A digital processor ( computer) connected

to 4.A miniature-milling machine ( 3-axis

machine)

CEREC1 6

Fabrication of simple inlays.

Very sharp internal angles of the restorations could not be administered.

Large grinding wheels associated with the original CEREC system.

The occlusal surface cannot be fabricated with CEREC 1.

CEREC 2 6

CEREC2 was significantly improved.

Addition of a further cylindrical grinder

Allowing the addition of occlusal pits and fissures.

Concave and biconvex contouring of veneers.

Occlusal surface can be ground with CEREC2

CEREC 3 6

Radiocontrolled operating system whereby the design and milling chamber units can be deployed separately.

Data acquisition and milling to be carried out simultaneously.

The milling unit of CEREC 3 is also equipped with laser scanner

A cylindrical floor and wall and a tapered cylindrical rotary diamond milling tool( coated with 64 µm-grit diamonds)

The angle of taper, which is 450, which is used to shape the occlusal surface of the restoration.

Simplifies occlusal and functional registration

CEREC 3D6

latest version.

allows a 3D view of the preparation and proposed restoration.

“ Self Adjusting Crown”

automated occlusion tool.

Superior marginal fit.

Precise Proximal Contacts.

Celay System uses a copy milling

technique to manufacture ceramic inlays or onlays.

A resin pattern is fabricated directly on the prepared tooth or on a master, the pattern is used to mill a porcelain restoration.

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As with the Cerec system, the starting material is a ceramic blank available in different shades

This material is similar to Vita Mark II ceramic, used with the Cerec 2 system.

Marginal accuracy seems to be good, a little better than the Cerec 2 system.

Procera AllCeram System6 -

The Pro cera AllCeram system involves an industrial CAD/ CAM process.

The die is mechanically scanned by the technician, and the data are sent to a work station where an enlarged die is milled using a computer-controlled milling machine.

This enlargement is necessary to compensate for the sintering shrinkage.

Aluminum oxide powder is then compacted onto the die, and the coping is milled before sintering at very high temperature (>1550° C).

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The coping is further veneered with an aluminous ceramic with matched thermal expansion.

The restorations seem to have good clinical performance and marginal adaptation, provided the scanning is done skillfully.

They may be suitable for posterior crowns and FPDs, although long-term data are needed.

Lava System 6 –

In a Lava System , a CAD/CAM procedure is used for the fabrication of zirconia frameworks all ceramic systems.

The preparations are scanned and frameworks are milled from presintered zirconia blanks.

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Non contact optical scanner

Lava milling unit LAVA THERM

Lava System 6–

The size of the frameworks is precisely increased to allow for the shrinkage that occurs during sintering.

Once a framework has been sintered, it is veneered with layered esthetic porcelains in a manner similar to that for the metal ceramic technique.

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Non contact optical scanner

Lava milling unit LAVA THERM

CERCON

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Master models are prepared in the same way as when fabricating crowns and bridges using precious dental alloys.

DeguDent Cergo die spacer (Order no. 6590 0001) is ideal as a spacer. One coat (thickness approx. 15 μm) of the die spacer is applied to the preparation surface of the die to approx. 1mm short of the preparation margin to allow a gap for the cement.

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Single crowns in the anterior region should have 0.3 mm wall thickness with a 0.2 mm marginal edge.Single crowns in the posterior region should 0.4 mm wall thickness with a 0.2 mm marginal edge.

Secure the pattern in the model frame.

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Powdering

Remove the model frame from the spindle.

Cover the pattern and sticks with scanning powder.

THE TECHNIQUE –Cercon eye

Means of data acquisition-Scanner

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LIMITATION

Three sizes of blanks are available12,30 and 38mmSo it can not be used for bridge longer than

38mm.

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166RECENT ADVANCES IN CERAMICS

SINGLE VISIT CROWN (CAD/CAM) –Using CERAC 3D

CEREC 3D uses CAD/CAM technology, incorporating a

camera, computer and milling machine in one instrument.

The dentist uses a special camera to take an accurate

picture of the damaged tooth.

This optical impression is transferred and displayed on a

color computer screen, where the dentist uses CAD

technology to design the restoration. Then CAM takes over

and automatically creates the restoration while the patient

waits.

Finally, the dentist bonds the new restoration to the

surface of the old tooth. 167

www.drsimonrosenberg.com www.dentsply.com

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Before After

What Are the Advantages CEREC 3D Offers? •The dentist performs the restoration in a single session, usually in about one-two hour(s).•No need for the dentist to make an impression and send it to a lab•No return visits for the patient•The restoration is natural looking, as it is made out of tooth-colored ceramic material

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Before After

What Are the Advantages CEREC 3D Offers?

•Ceramic material is biocompatible, high-grade, anti-abrasive and plaque-resistant.•Metal-free -- no silver-colored fillings.•Allows dentist to save more of the healthy tooth•Extremely precise

CONCLUSION The difference with & without Ceramics is self evident

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REFERENCES

1) The glossary of prosthodontic terms. J Prosthet Dent 2005; 94(1):62

2)Kenneth J. Anusavice; PHILLIPS’ SCIENCE OF

DENTAL MATERIALS; 11TH edition; Page 655-718.

3) Robert G. Craig & John M. Powers; RESTORATIVE

DENTAL MATERIALS; 12TH edition; Page 430-500.

4)Rosenstiel, Contemporary Fixed Prosthodontics;

Third Edition, Mosby Elsevier India; page 740-804.

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5. Herbert T. Shillingburg, Jr, Fudamentals of Fixed Prosthodontics;Third Edition, Quintessence Publishing Co, Inc; page no.433-484.

6. www.dentsply.com

7. Oh WS, Delong R, Anusavice KJ.Factors affecting enamel and ceramic wear: A literature review.J Prosthet Dent 2002 Apr;87(4):451-9

8. . Cristopher CK.shade selection.aust dent prac. 2007;116-119

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9. Rosenstiel. Apparent fracture toughness of metal ceramic restorations with different manipulative variables. J Prosthet Dent 1989 Feb;61(2):185-91.

10. Kelly JR. Dental ceramics: currennt thinking and trends. Dent Clin N Am 48(2004)513-530.

11.Font Antonio. Choice of ceramic for use in treatments with porcelain laminate veneers. Med Oral Patol Oral Cir Bucal. 2006;11:E297-302.

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12 .Denry il. Recent advances in ceramics for dentistry. Crit rev oral biol med.1996;7(2):134-143.

13.Vagkopoulou t. zirconia in dentistry part 1. discovering the nature of upcoming bioceramic. European journal of esthetic dentistry. 2009(4); 2-22.

14. Fasbinder J D, Dennison J B,Heys D and NeivaA G. Clinical Evaluation of Chairside Lithium Disilicate CAD/CAM Crowns : A Two-Year REPORT.JADA 2010;141(suppl 2):10S-14S

15. Dentsply. Crown and bridge laboratory training guide.

16. VITA VMK Master® Working Instructions.

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17.Conrad H,Seong W ,and Pesun I. Current ceramic materials and systems with clinical recommendations: A systematic review. J Prosthet Dent 2007;98:389-404.

18 www.google.com/image

19.Raigrodski AJ. Contemporary all-ceramic fixed partial dentures: a review. Dent Clin N Am. 2004; 531-544.

20.Hench L L.Bioceramics: From Concept to Clinic. J.Am. Ceram.Soc.1991;74:1480-510.

21. Capa N. An alternative treatment approach togingival recession: gingiva-colored partialporcelain veneers: A clinical report. J Prosthet Dent 2007;98:82-84.

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