METAL FREE CERAMICS- AN UPDATE

METAL FREE CERAMICS- An Update

DR. SHAHEEN.V2ND MDS,Conservative Dentistry And Endodontics

FLOW CHART• INTRODUCTION

• DEFINITIONS

• HISTORY

• COMPOSITION OF CERAMICS

• CLASSIFICATION

According To Type

According To Firing Temperature

According to Substructure material

According to the technique of Fabrication.

• PROPERTIES

Esthetics

Chemical stability

Shrinkage

Co efficient of thermal expansion of porcelain

Brittleness

Dimensional stability

Effect of moisture contamination

Degradability

Abrasion resistance

• STRENGTHENING OF CERAMICS

Conventional powder slurry systemLeucite Reinforced feldspahtic porcelainAluminous based porcelain Alumina reinforced porcelainMagnesia based feldsphatic porcelain Zirconia based Porcelain Hydrothermal low fusing ceramics

Slip Cast CeramicsAlumina based (IN-CERAM)IN-Ceram SpinellIN-Ceram Zirconia

Injection molded ceramics. Leucite Based Spinel based

Machinable ceramics

1. DIGITAL

CAD CAM

Cerec

2. ANALOGOUS

Copy Milling

Celay

• COMPARISON OF DIFFERENT METAL FREE CERAMIC SYSTEMS

Fabrication techniques

Strength

Marginal fit

Wear of opposing tooth structure

• CLINICAL APPLICATION AND SELECTION CRITERIA

• CEMENTATION OF METAL FREE CERAMICS

• ADVANTAGES AND DISADVANTAGES

• REVIEW OF LITERATURE

• CONCLUSION

• REFERENCES

INTRODUCTION

• Dental ceramics are materials that are part of systems designed with the purpose of producing dental prostheses that in turn are used to replace missing or damaged dental structures.

• Metal ceramic restorations have been available for more than three decades. This type of restoration has gained popularity from its predictable performance and reasonable esthetics.

• Despite its success, the demand for improved esthetics and the concerns regarding the biocompatibility of the metal has lead to the introduction of all-ceramic restorations.

Dental ceramic: An inorganic compound with non metallic properties typically consisting of oxygen and one or more metallic or semimetallic elements (eg. aluminum, calcium, lithium, magnesium, potassium, silicon, sodium, tin, titanium and zirconium) that is formulated to produce the whole or part of a ceramic based dental prosthesis.

• Anusavice, phillips science of dental materials, 12th edition, 2012

TERMINOLOGIES

• Feldspathic porcelain

A ceramic composed of a glass matrix phase and one or more crystalline phases (such as leucite, K2OAl2O34SiO2).

• Glass

An inorganic nonmetallic compound that lacks a crystalline structure.


• Glass-ceramic

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

• Sintering

The process of heating closely packed particles to a specified temperature to densify and strengthen a structure as a result of bonding, diffusion, and flow phenomena

• Glass-infiltrated ceramic

A minimally sintered core ceramic with a porous structure that has been densified by the capillary inflow of a molten glass.


• Glass-infiltrated ceramic

A minimally sintered core ceramic with a porous structure that has been densified by the capillary inflow of a molten glass.

• Castable ceramic

A glass or other ceramic specially formulated to be cast into a refractory mold to produce a core coping or core framework for a ceramic prosthesis.

• Core ceramic

An opaque dental ceramic material that provides sufficient strength, toughness, and stiffness to support overlying layers of veneering ceramics.


• Pressable ceramic (hot-pressed ceramic)

A ceramic that can be heated to a specified temperature and forced under pressure to fill a cavity in a refractory mold.

• Slip casting

A process used to form "green" ceramic shapes by applying a slurry of ceramic particles and water or a special liquid to a porous substrate (such as a die material), thereby allowing capillary action to remove water and densify the mass of deposited particles.

• Spinel/ Spinelle

A crystalline mineral composed of mixed oxides such as MgAl2O4 (MgOAI2O3). • Anusavice, phillips science of dental materials, 12th edition, 2012

• Copy-milling

The process of cutting or grinding a structure using a device that traces the surface of a master metal, ceramic, or polymer pattern and transfers the traced spatial positions to a cutting station where a blank is cut or ground in a manner similar to a key-cutting procedure.

• CAD-CAM

A ceramic that is formulated for the production of the whole or part of an all-ceramic prosthesis through the use of a computer-aided design and computer-aided manufacturing process.


HISTORY

History of porcelain use in dentistryThe use of porcelain in dentistry was first mentioned by Pirre Fauchard. The superior surface and colouring qualities were used by fusing the material to gold or silver.

• 1728 – Pierre Fauchard, a French dentist first proposed the use of porcelain in dentistry. He suggested the use of jeweler’s enamel to fabricate artificial teeth.

• 1774 – Alexis Duchateau, a French apothecary with the assistance of a Parisian dentist Nicholas Dubois de Chemant, made the first recorded successful porcelain dentures at the Guerhard Porcelain Factory.

1788 - Nicholas Dubois de Chemant continually improved porcelain formulations and first displayed a baked porcelain denture made in a single block. Published his book on artificial teeth.1789 – Fused porcelain was introduced for manufacture of teeth.

1806 to1808 – Giuseppangelo Fonzi an Italian dentist who worked in Paris introduced - ‘terrometallic’ porcelain tooth.1837 – John Murphy of London introduced the plantium foil technique

1884 – Dr Charles H.Land pionerred the development of the first glass furnace for fusing porcelain.

1887 – Dr C.H.Land of Detroit developed the first all-porcelain jacket crown (PJC) using the Platinum Foil Matrix techniqe

1889 – Dr.Charles H. Land patented the Plantinum Foil Matrix techniqe for PJC.

1903 – E.B.Spaulding developed gingival shoulder porcelain for the PJC

1962 - M.Weinstein, S. Katz & A. B. Weinstein were awarded the U.S patent for gold alloy formulation and feldspathic porcelain designed for porcelain fused to metal restoration.

1963 to 1965 – The first viable technique for Alumina-reinforced crowns was develoed by McLean &Hughes in England

1976 – McLean & Sced developed the stronger platinum bonded alumina crown. The attachment of aluminous porcelain to the platinum was achieved by surface coating of the metal with a thin layer of tin.

1985 – First CAD/CAM crown was publically milled and installed in the mouth.1985 – Hobo & Kyocera (Biocream group ) developed a castable glass-ceramic which melts at 14600C and flows like molten glass.1986 – The first generation CEREC 1 (Siemens) CAD/CAM system was introuced.1988 – Michael Sadoun first introduced In-ceram, a glass-infiltreated aluminous porcelain.1989 – Duceram LFC, a low fusing Hydrothermal ceramic was introduced1992 – The Celay copy-milling system (Mikrona AG), became commercially available.

Sintering—Process of heating closely packed particles below their melting temperature to promote atomic diffusion across particle boundaries and densification of the mass.Ceramming is a controlled crystallization of the glass that results in the formation of tiny crystals that are evenly distributed throughout the body of the glass structure. The size of the crystals, as well at the number and rate of growth is determined by the time and temperature of the ceramming heat treatment.Incongruent melting occurs when a substance does not melt uniformly and decomposes into another substance. For example, potassium feldspar(KAlSi3O8) decomposes to leucite (KAlSi2O6) when it melts. Congruent melting occurs during melting of a compound when the composition of the liquid that forms is the same as the composition of the solid

1994 – The second generation CEREC 2 (Siemens/Sirona) CAD/CAM System was presented.

Late 1990’s – IPS Empress 2, a second generation pressable ceramic made from lithium-disilicate frame work with an apatite layered ceramic was introduced.

1997 – IPS Empress Cosmo Ingot (Ivoclar) , a glass-ceramic material that can be heat pressed directly onto zirconia posts (eg; Cosmopost) was introduced .

1999 – IPS SIGN (Ivoclar AG), a feldspar-free fluorapatite glass ceramic system for use in metal-ceramics was presented.

• 2001- CERCON from Dentsply International introduced dental restorations from unsintered yttrium stabilized zirconia based ceramic core material

• 2001- Lava™ by 3M™ ESPE™

• 2004- Lava™ Classic by 3M™ ESPE™

• 2006-Lithium disilicate re-emerged in 2006 as a pressable ingot and partially crystalized milling block

• 2007- ITERO by Cadent as the first digital impression system for conventionally manufactured crown and bridges.

• 2008- E4D Dentist system by D4D technologies, is presently the the only other system besides CEREC that permits same day in- office restoration.

• 2012- Lava™ Plus by 3M™ ESPE™ is based on a unique 3M™ ESPE™ shading technology

• 2014- Lava™ Ultimate is a resin nano ceramic-a new class of CAD/CAM material with unique functionality having an elastic modulus that is comparable to dentin

CLASSIFICATION• ACCORDING TO TYPE:

• Feldspathic porcelain• Aluminous porcelain• Glass infiltrated aluminous• Glass infiltrated spinel• Glass ceramics

• ACCORDING TO FIRING TEMPERATURE:• High fusing > 1300 c• Medium fusing 1101 –1300 C• Low fusing 850 – 1101 C• Ultra low fusing <850 C.• Anusavice, phillips science of dental materials, 12th edition, 2012

According to application

• For porcelain teeth

• For Ceramo-metal restorations (Metal-Ceramic Systems),

• For All-ceramic restorations (All-Ceramic System).

R.W. Phillips, 1982, Skinner’s 8Th edition

According to the technique of Fabrication

1. Conventional Powder and slurry ceramics : using condensing sintering• Alumina reinforced porcelain : Hi-ceram • Magnesia reinforced porcelain : Magnesia cores. • Lucite reinforced (high strength) : Optic HSP. • Zirconia whisker – fiber reinforced : Mirage II. • Low fusing ceramics • Hydrothermal LFC : Duceram

2.Castable ceramics - Using casting and Ceramming

(Rosenblum and Alan Schulman. A review of all ceramic restorations JADA March 1997)

• Fluromicas – Dicor.

• Apatite based glass – Cera Pearl.

Other glass ceramic : Lithia based, CaPO4 based.

3 Machinable ceramics : Milling machining of mechanical digital control.

A. Analogous systems (Pantograph system – copying methods)

• Copy milling / grinding technique • Mechanical – Celay • Automatic – Ceramatic II DCP.

• Erosive techniques • Sono-erosion : DFS, Erosonic. • Spark – erosion : DFS, Procera.

B Digital systems (CAD/CAM)

• Direct- ex :Cerac 1 and cerac 2

• Indirect- ex: Ceciro, Denti CAD, Automill, DCS – President

4. Pressable ceramics -By pressure molding and sintering.

• Shrink free alumina reinforced ceramic (injection molded)

Cerestore / Al Ceram.

• Leucite reinforced ceramic (Heat-transfer molded).

IPS express, IPS Impress 2 and OPTEC OPC.

5. Infiltrated ceramics : By slip casting, sintering glass infiltration.

• Alumina based :In Ceram alumina

• Spinal based : In Ceram spinal.

• Zirconia based : In Ceram zirconia.

STRUCTURE

ceramics

Crystalline

Eg : Aluminous

Non-crystalline

Eg : (Glasses) Feldspathic porcelain

CRYSTALLINE CERAMICS• The only true crystalline ceramic used in restorative

dentistry is Alumina (A12O3) which is one of the hardest and probably the strongest oxides known.

• The hardness and strength of alumina makes it difficult to cleave because of the interlocking nature of the structure.

• Ceramics are reinforced with crystalline inclusions such as alumina and leucite into the glass matrix to form crystal glass composites as a part of strengthening the material and improving its fracture resistance

NON-CRYSTALLINE CERAMICS

• Ceramic is usually silicate in nature and hence defined as a combination of one or more metals with a non-metallic element, usually oxygen.

• Ceramic crystals show both ionic and covalent bonds

• These strong bonds are responsible for

• Stability, Hardness, High Modulus Of Elasticity, Resistance To Heat & Chemical Attack

Feldspathic porcelain• Of all the currently available esthetic restorative materials,

feldspathic porcelains are closest in matching the translucency and the shade of enamel

• All the dental porcelains show a reduction in the Kaolin content (to reduce opacity ) and an increase in the feldspar content (to improve their translucency ). Hence dental porcelains can be more appropriately considered as “Feldspathic glasses with crystalline inclusions of silica”.

• Feldspathic Porcelains are glasses based on the Na2O-K2O- Al2O3- SiO2 system.

• This non-crystalline material is inherently brittle and prone to fracture.

PROPERTIES OF DENTAL CERAMICS• CHEMICAL STABILITY –It is chemically inert.

But some form of topical fluoride can damage the porcelain like 1.23 % acidulated phosphate fluoride(APF) or 8% stannous fluoride etches the glass matrix making it dull and rough.

• SHRINKAGE

On heating- linear shrinkage 11.5 % in high fusing porcelain and 14 % in low fusing porcelain.

Minimized by using lesser binder , proper condensation, build – up of restoration 1/3rd larger than original size and firing in successive stages.

Operative Dentistry: Modern Theory & Practice by M.A.Marzouk- first edition

• COLOUR STABILITY

Ceramics are the most stable tooth colored materials. The metallic oxides used as colorants do not undergo any change in shade after firing is complete. The smooth glossy surface resists the adherence of exogenous stains.

• BRITTLENESS

Is the relative inability of a material to sustain plastic deformation before fracture of the material occurs. Ceramics are brittle at oral temperatures (50 to 550 C ) Brittle materials such as dental ceramics fail because of the formation and growth of macroscopic flaws that can form during fabrication or in service.


CO EFFICIENT OF THERMAL EXPANSION OF PORCELAIN

(12-13 x 10⁻⁶⁰c)

It should be lower than that of the casting alloy to keep the porcelain in residual compression upon cooling from firing temperature.

ABRASION RESISTANCE

Fused porcelain is the hardest dental material in common use. It will cause metal restorations and tooth structure to wear more rapidly; particularly when not adequately glazed or when glaze is removed during occlusal adjustment (should be smoothened by polishing).


Compressive strength of porcelain is good but has a poor tensile strength because of the surface defects like porosities and microscopic cracks. So when place under tension stress concentrates around these imperfections resulting in fracture.

Flexure strength Ground 75.8 Mpa Glazed 141.1 Mpa

Compressive strength 331 Mpa

Tensile strength 34 Mpa

Shear strength 110 Mpa

Modulus of elasticity 60-70 Mpa

Surface hardness 460 KHN ,611-703 VHN

Coefficient of thermal expansion Feldspathic 6.4-7.8 x 10⁻⁶/°c Reinforced12.38 – 16.23 x 10⁻⁶/°c

Thermal conductivity 2.39 Mcal / s (cm2) °c/cm

Specific gravity 2.2- 2.3

Strengthening Of Ceramics • Ceramics fail at much lower forces because of minute

surface scratches and defects on surface

• Stress concentration on the tips of these scratches , so when there is localized increase in stress concentration it will initiate crack formation .

The condensation, melting and sintering process.

The high contact angle of ceramics on metal.

Differences in the coefficient of thermal expansion between alloy or core and veneers.

Tensile stresses during manufacture , function and trauma• Anusavice, phillips science of dental materials, 12th edition, 2012

METHOD TO OVERCOME

Methods of strengthening brittle materials

Designing components to decrease stress concentration

Development of residual compressive stresses

Interruption of crack propagation

1. Dispersion of crystalline phase

2. Transformation toughening

1. Ion exchange

2. Thermal tempering

3. Thermal compatibility

Anusavice, phillips science of dental materials, 12th edition, 2012

Development of residual compressive stress

• Ion exchange or chemical tempering • Exchange of small Na ions with larger K ions (35%

larger )

• A sodium-containing glass article is placed in a bath of molten potassium nitrate. K+ ions in the bath are exchanged with Na+ ions on the surface of the glass articleAnusavice, phillips science of dental materials, 12th

edition, 2012

• Thermal tempering • By rapid cooling (quenching ) the surface of the object

while it is hot and in the softened (molten ) core . • This rapid cooling produces a skin of rigid glass

surrounding a soft (molten) core .

• For dental application – it is more effective to quench hot glass-phase ceramics in silicone oil or special liquids rather than using air jets that may not uniformly cool the surface Anusavice, phillips science of dental materials, 12th

edition, 2012

Thermal compatibility

• Principle – Slight mismatch between the coefficient of thermal contraction of the core and veneering ceramic material places the outer layer under slight compressive stress rather than tensile stress.

• Thermal coefficient of contraction of the core ceramic is slightly greater than the thermal coefficient of contraction of the veneering ceramic ( such as opaceous dentin or body /gingival porcelain .

Interruption of crack propagation Dispersion of a crystalline phase

• If a ceramic crystals of high strength and elasticity are dispersed in the glass phase of dental ceramic these harder masses interfere with crack propagation .

• McLean and Hughes in 1965 , developed a high strength core porcelain using this principle .

• There should be close match of coefficient of thermal expansion between the crystalline material and the surrounding glass matrix .

• When a tough crystalline material such as alumina (Al2O3) in particulate form is added to glass, the glass is toughened and strengthened.

• O’Brien in mid 1980 – used magnesia crystals to reinforce a glass

• Other crystals which are used are • Leucite • Lithia disilicate • Zirconia Anusavice, phillips science of dental materials, 12th

edition, 2012

Transformation toughening • Dental ceramics based primarily on zirconia crystals (ZrO2)

undergo transformation toughening that involves a transformation from a tetragonal crystal phase to a monoclinic phase at the tip of the cracks that are in the regions of the tensile stress .

Anusavice, phillips science of dental materials, 12th edition, 2012

TRANSFORMATION TOUGHENING

The transformation of partially stabilized tetragonal zirconia into the stable monoclinic form can also occur under stress and is associated with a slight particle volume increase.

CONVENTIONAL POWDER/

SLURRY CERAMICS

These products are supplied as powders to which the technician adds water to produce a slurry, which is built up in layers on a die material to form the contours ofthe restoration. The powders are available in various shades and translucencies, and are supplied with characterizing stains and glazes.


TYPES :• Alumina – Reinforced porcelain (Aluminous

Porcelain) · Hi-Ceram (vident), · Vitadur – N core (vident)

• Magnesia – Reinforced porcelain (magnesia core ceramics)

• Leucite Reinforced (Non-pressed) · Optec HSP (jeneric/pentron)· Optec VP (jeneric/pentron)· Fortress (Mirage int)(Rosenblum and Alan Schulman. A review of all ceramic restorations JADA

March 1997)

• Low fusing ceramics Hydrothermal Low- fusing ceramic • Eg: Duceram LFC (Ducera)• Finesse (Ceramco inc).• Zirconia reinforced Ceramics• Eg .Mirage II (Myron int, Kansas).

• Alumina based ceramic

McLean and Hughes (1965) -Alumina-reinforced porcelain core material for the fabrication of ceramic crowns.

Objective

• Improve aesthetics by a replacement of the thicker metal coping with a thin platinum foil, thus allowing more room for porcelain

• The first aluminous core porcelains contained 40% to 50% alumina by weight.

John W.

McLean,September 1967, JADA

MASTER MODEL WITH DIE PLATINUM FOIL ADAPTED TO DIE

PLATINUM FOIL ADAPTED TO DIE FINISHED

CORES

DENTIN CERAMIC ADDITIONS

UNSINTERED CROWNS

FINISHED CROWNS ON DIES POST CEMENTATION

• Bonding aluminous porcelain to platinum foil copings by use of tin oxide coatings on platinum foil.

• Bonded foil – Acts as an inner skin on the fit surface

-- Reduces subsurface porosity and formation of micro cracks in the porcelain

-- Increasing the fracture resistance of crowns and bridges.

• The clinical performance of these crowns has been excellent for anterior teeth, but approximately 15% of these crowns fractured within 7 years after they were cemented to molar teeth with a glass ionomer cement

Disadvantages of Aluminous porcelain

• Poor esthetics ( Used as a core only).• Extensive reduction, dentin preparation.• Bonding is limited.

• Porcelain used for veneering in PFM cant be used with aluminous core porcelain:

• CTE Alumina core: 8x 10-6/0C • Hence requires similar low expansion veneer porcelain.

• CTE Veneering porcelain for PFM: 13 x 10-6/0C• Extensive cracking results upon bonding these materials

owing to thermal stresses.

Leucite reinforced feldspathic porcelain Optec HSP (jeneric / Pentron )

Optec HSP is a feldspathic porcelain with 45% volume tetragonal leucite

The greater leucite content of optec HSP porcelain compared with conventional feldspathic porcelain for metal ceramic leads to higher modulus of rupture and compressive strength.


ADVANTAGES

Good transluency compared to alumina crowns

Moderate flexural strength (146 Mpa) higher than conventional feldspathic porcelain

DISADVANTAGES

Marginal in accuracy caused by marginal porcelain sintering shrinkage

Potential to fracture in posterior teeth

Increased leucite content may cause relatively higher in vitro wear of opposing teeth

USES

Employed for Inlays, Onlays, Crowns for low stress areas and Veneers

Magnesia based core porcelains

Magnesia core porcelains was developed as an experimental material in 1985 (O'Brien, 1985).

Magnesia was used as the basis of high expansion core material because co efficient of thermal expansion of magnesia is 13.5 X 10 -6/°c.

• The core material is made by reacting magnesia with a silica glass within the 1100-1150°C temperature range.

• This treatment leads to the formation of Forsterite (Mg2Si04) in various amounts, depending on the holding time. The proposed strengthening mechanism is the precipitation of fine forsterite crystals (O'Brien et al, 1993)

The difference is explained on the basis that, magnesia has face centered cubic structure , whereas alumina has hexagonal close packed structure .

Strengthening is achieved by dispersion strengthening by the magnesia crystals in vitreous matrix and also by crystallization within the matrix .

• Its high thermal expansion coefficient closely matches that of body and incisal porcelains designed for bonding to metal (13.5 x 10"6/°C).

• The flexural strength of unglazed magnesia core ceramic is twice as high (131 MPa) as that of conventional feldspathic porcelain (65 MPa).

• The magnesia core material can be significantly strengthened by glazing, thereby placing the surface under residual compressive stresses that have to be overcome before fracture can occur .

(Wagner et al, 1992).

ZIRCONIA BASED CERAMICS

MIRAGE ƖƖ (MYRON INTERNATIONAL ,KANSAS CITY)

Conventional feldspathic porcelains where tetragonal Zirconia fibres have been .

Zirconia undergoes a crystallographic transformation from monoclinic to tetragonal at 1173°C.

Partial stabilization can be obtained by using various oxides such as CaO, MgO, Y2O3, and CeO, which allows the high-temperature tetragonal phase to be retained at room temperature

MECHANISM OF STRENGTHENING

Zirconia undergoes a crystallographic transformation from tetragonal to monoclinic at 1150° C. The translation of partially stabilized tetragonal zirconia into stable monoclinic form can also occur under stress. The result of this transformation is that there is slight particle volume increase resulting in compressive stress that is established on the crack surface ,there by inhibiting its growth .

HYDROTHERMAL CERAMICS

• The hydrothermal ceramic systems are basically low fusing porcelains containing hydroxyl groups in the glass matrix.

• The hydroxyl ion is added to the porcelain structure through exposure to water or water vapours.

• The hydroxyl addition which Bertschetein and Stepanov termed as “a plasticized layer” supposedly increases chemical resistance; generates “smoother” surface profile, and possesses the unique capacity of “healing” surface flaws through the ion exchange process.

Hydrothermal ceramics can be formulated as two types :

A single phase porcelain

• Eg: Duceram LFC® (Degussa Dental, South Plainfield, NJ)

A leucite containing two phase material

• Eg.: Duceragold® (Degussa Dental, South Plainfield, NJ)

• Self healing effect of hydroxyl surface layer : Conventional porcelains contain surface microflaws or develop them after exposure in the oral environment. These flaw can increase over a time period, resulting in surface dicolourations and reduction in flexural strength. In hydrothermal ceramics an ionic exchange occurs between alkali and hydroxyl groups at the surface layer. This ionic exchange is suggestive of an effect of “healing” surface flaws, thereby contributing to an increase in strength.

• Duceram LFC: is a low fusing hydrothermal ceramic composed of an amorphous glass containing hydroxyl (-OH) ions.

• It was developed in mid 1980’s based on the ideas and studies on industrial porcelain ceramic from the early 1960’s and was first introduced to the market in 1989 for use in all ceramic prostheses, ceramic / metal-ceramic inlay and partial crowns.

• Fabrication of a Duceram ceramic restoration: Two layers of ceramics are to be applied. The base layer - Duceram MC ( Duceram Metal Ceramic ); a Luecite containing porcelain, followed by the veneer - Duceram LFC (Duceram Low Fusing Ceramic); a low fusing hydrothermal ceramic.

• Method: Duceram MC is condensed on a refractory die using conventional powder slurry technique and sintered at 930oC. Over this base layer, Duceram LFC is condensed and sintered at 660o C. Being highly polishable they do not require glazing.

CASTABLE CERAMICS• DICOR (Dentsply Int.)

• CERA PEARL (Kyocera)

• Glass ceramic are composite materials of glassy matrix and a crystal phase .

• A glass -ceramic is material that is formed into the desired shape as a glass, then subjected to a heat treatment to induce partial devitrification (ie loss of glassy structure by crystallization of the glass).

• The crystalline particles, needles, or plates formed during this process serve to interrupt the propagation of cracks in the material when an intraoral force is applied, thereby causing increased strength and toughness.

• The use of glass-ceramics in dentistry was first proposed by MacCulloch in 1968

• The first commercially available castable ceramic material for dental use, Dicor, was developed by Corning Glass Works and marketed by Dentsply International.

Arvind Shenoy, Journal of Conservative Dentistry | Oct-Dec 2010

• Dicor system composed of SiO2; K2O. MgO, and MgF2. Small amounts of Al2.O3 and ZrO2 are added for durability and a fluorescing agent is added for esthetics.

• Dicor contain Tetra silicic fluor mica Crystals

• Lost wax casting technique is used , similar to that employed for metals.

• Uses centrifugal casting machine.

• Glass subjected to heat treatment (1075 degree c for 10 hrs) that causes microscopic plate like crystals of crystalline material to grow with in the glass matrix

• Crystallization-65%, crystal is Tetra silicic fluor mica Crystals.

• This heat treatment (which involves crystal nucleation and crystal growth process) is known as “ceramming”.

• The crystals function in 2 ways:

1) They create a relatively opaque material out of initially transparent crown,

2) They significantly increase the fracture resistance and strength of ceramic. These crystals are also less abrasive to opposing tooth structure than the leucite crystals found in traditional feldspathic porcelains

• Dicor is a glass, it is capable of producing a “Chameleon Effect” i.e. part of the colour of the restoration is picked up from the adjacent teeth as well as from the cement used for luting the restoration.

• The transparent crystals scatter the incoming light and also its color, 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

Chameleon Effect

Frank Spear, JADA, Vol. 139 September 2008

WAX PATTERN

SPRUCING

INVESTING(PO4)

BURNOUT

Centrifugal casting 13500 C 4mins

Divesting25micron , 40psi

Cast glass coping Ceramming

CERAMMING CERAMMING OVEN

CRYSTALLIZED GLASS COPING

• Ceramming done from 650-1075°c for 1½ hrs and sustained for 6hrs in order to form tetra silicic flouromica crystals

• This procedure leads to controlled crystallization by internal nucleation and crystal growth of microscopic plates like mica crystals within the glass matrix.

• Advantages -

• Ease of fabrication

• Improved aesthetics

• Moderately high flexural strength

• Low thermal expansion equal to that of tooth structure

• Minimal abrasiveness to tooth

• Biocompatibility

• Less bacterial counts

Disadvantages

Its limited use in low-stress areas

Its inability to be coloured internally.

Hydroxyapatite based castable glass ceramics: cerepearl

Cerapearl was developed by Sumiya Hobo and Kyocera Bioceram group of Kyoto city ,Japan

The main crystalline phase is oxylapatite ,transformable into hydroxyapatite when exposed to moisture.

It melts at 1460ºC and flows like a melting glass

The cast material has an amorphous microstructure and when reheated at 870ºC forms a crystalline hydroxyapatite .


Because of its crystalline constituent similar to natural enamel ,its biocompatible

Crystals of enamel have a regular arrangement wheras crystals of cerapearl have an irregular arrangement

Hence has a same crystal component as enamel but has a superior mechanical strength.

Cerapearl is very white in comparison with natural tooth enamel and requires application of external stain

Cerestain by bioceram is designed for this purpose

PRESSABLE GLASS CERAMIC

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

Are of 2 types

• Shrink-free Ceramics Leucite-reinforced Glass ceramics

Cerestore IPS Empress

AI-Ceram Optec Pressable Ceramic (OPC)


CERESTORE Non-Shrink Alumina Ceramic

Is a shrink-free ceramic with crystallized Magnesium Alumina Spinel fabricated by the injection molded technique to form a dispersion strengthened core.

Composition Of Shrink Free Ceramic

Unfired Composition Fired Composition (Core)

A12O3 (Corundum) 60%MgAl2O4 (Spinel) 22%BaMg2A13(Barium Osomilite) 10%

Al2O3 (small particles) 43%Al2O3 (large particle) 17%MgO 9%Glass frit 13%Kaolin Clay 4%Silicon resin (Binder) 12%Calcium Stearate 1%

• On firing a combination of chemical and crystalline transformation produces Magnesium aluminate spinel, which occupies a greater volume than the original mixed oxides (raw ingredients), and thus compensates for the conventional firing shrinkage of ceramic.

• Chemical transformation: During firing from 160°C to 800°C, the silicone resin (binder) converts from SiO to SiO2 which in turn combines with alumina to form aluminosilicate.

• Crystalline transformation: The primary inorganic reaction involves MgO, Al2O3 and the glass frit. The aluminosilicate formed

ALUMINA + MAGNESIA MAGNESIUM ALUMINATE SPINEL

(Al2O3) (MgO) (MgAl2O4)

Fabrication:

• By Transfer Molding process which is identical to injection molding of acrylic resin denture bases. Copings are formed by transfer-molding the ceramic directly onto non-shrinking heat stable epoxy master dies

• The wax pattern on the epoxy die is sprued, invested and burned out.

• The flask is placed on a heating element (oven) and removed after it reaches the molding temperature.


• Shrink-free ceramic material supplied as dense pellets is heated until the silicone resin binder is flowable (160°C) and then transferred by pressure (under a plunger) directly on the master die. The silicone resin binder is thermoplastic and thermosetting, hence after injection into the mold and around the master die, it automatically sets.

• The flask is quenched and the ceramic coping is fired in a micro-processor controlled furnace (1300°C) to achieve zero-shrinkage.

• The sintered coping is replaced on the die and veneered with conventional aluminous porcelain.

IPS Empress

This technique was first described by Wohlwend & Scharer; and marketed by Ivoclar (Vivadent Schaan, Liechtensein).

• Is a pre-cerammed, pre-coloured leucite reinforced glass-ceramic formed from the leucite system (SiO2-AI2O3-K20) by controlled surface crystallization, subsequent process stages and heat treatment

• The partially pre-cerammed product of leucite-reinforced ceramic powder available in different shades is pressed into ingots and sintered. The ingots are heated in the pressing furnace until molten and then injected into the investment mold.


• Following the burn out procedure, the ring along with the investment is placed In a specialized mould that has an alumina plunger

• The ceramic ingot is placed under the plunger .

• The entire assembly is heated to 1150°C and the plunger presses the molten ceramic into the mould

The cylinder is then pressed under vacuum into the mould and held under pressure to allow complete and accurate fill of the investment cavity

The crown is formed in dentin shades

Enamel layering is added in Empress furnace for necessary translucency

and staining .

Ips empress ii

FRANK et al 1998 ,EDELHOFF et al 1999, POSPEICH et al 1999

Indicated in all ceramic bridges ,anterior and posterior crowns

It is similar except that the core contains Lithia disilicate crystals in a glass matrix and veneering ceramics contains apatite crystals

The lithium disilicate has an unusual microstructure in that it contains very small inter locking crystals that are very randomly oriented

This is ideal from point of view of strength because the needle like crystals cause cracks to deflect, blanch or blunt thus propagation of cracks through this material is arrested by lithium disilicate crystals ,providing substantial increase in flexural strength.

A second crystalline phase containing of a lithium ortho phosphate ( li3po4) of a much lower volume is also present

The high strength creates the possibility of not only creating anterior and posterior crowns but also posterior bridges .

PROPERTY

• Core ceramic • Veneering ceramic• Processing

temperature

IPS Empress

• Glass ceramic with 35% volume of leucite crystals

• Also contains leucite crystals in glass matrix

• 1180° C

IPS EmpressII

• Glass ceramic with 70% volume of lithium di silicate crystals Li3po4 in much lower concentration

• Contains apatite crystals which causes light scattering similar to tooth stucture

• 920°C

In Empress I the leucite core ceramic is identical to the veneering ceramic so a mismatch in co efficient of thermal expansion does not arise. However for Empress II co efficient of thermal expansion is greater ,hence a compatible layering ceramic had to be developed. This new layering is an apatite glass ceramic

The apatite crystals influence the translucency ,brittleness and light scattering ability of layering ceramics. The material has improved density and handling characteristics


Empress esthetic

Lee cup et al

A newer leucite reinforced glass ceramic with a broader ingot shade range ,greater homogeniety ,greater density ,greater flexural strength

When used with traditional staining techniques it provides better esthetics

When coupled with IPS Empress Esthetic veneering materials and Empress esthetic wash pastes, provides life like translucency of the restoration .

Features

Broader ingot shade range

Greater homogeneity

Greater density

Greater flexural strength

Chameleon effect

Natural translucency and fluorescence

Excellent press results

IPS e . Max

The new all ceramic system (lithium disilicate) from ivoclar vivadent ,which is marketed under the brand name IPS e .max for the press and CAD CAM technology.

COMPOSITION• quartz, lithium dioxide,

• phosphor oxide, alumina,

• potassium oxide other components

• 70% needle like crystals embedded in glass matrix approximately 3-6 µm in length.

PROPERTIES of lithium disilicate (LS2)

1. Highly aesthetic

2. Highly thermal shock resistant glass ceramic due to the low thermal expansion.

3. High strength material that can be cemented or bonded.

4. Offers a unique solution with its ability to offer a full contour restoration fabricated from one high-strength ceramic, thereby eliminating the challenge of managing 2 dissimilar materials.

GLASS INFILTRATED CERAMICS

Slip Cast Ceramics(glass Infiltrated Ceramics)

INCERAM FAMILY

Inceram alumina

Inceram spinel

Inceram zirconia

Inceram sprint


• Developed by a French scientist and dentist Dr. Michael Sadoun (1980) A Slip is a suspension of fine insoluble particles in a liquid

• The In-Ceram Crown (Vident) process involves three basic steps :

• Making an intensely dense core by slip casting of fine grained alumina particles and sintering.

• The sintered alumina core is infiltrated with molten glass to yield a ceramic coping of high density and strength.

• The infiltrated core is veneered with feldspathic porcelain and fired

In ceram Alumina Slip casting :

• A special ultrasonic device (In-Ceram Vitasonic II), Liquid (water), fine grained (1-5um) alumina powder and an additive are combined and stirred under ultrasonic agitation to give a homogenous mass

• The slip is painted on a special plaster model made of porous refractory matrix (In-Ceram Special Plaster) needed to compensate for the sintering shrinkage of the slip.

• As the liquid from the slip cast is absorbed into the die by capillary action, additional layers are added (0.5 to 0.7mm thick).

• Framework is shaped roughly before the first firing.

• The alumina layer is allowed to dry (30 mins),

• Sintering (10 hour firing cycle of upto 1120 0C) in a special furnace (In-Ceramat) to produce an organized microstructure. The coping is fragile and porous in nature.

Glass - infiltration

• A specially formulated low-fusing glass-infiltrate (lanthanum glass) powder is mixed with distilled water.

• The frameworks are set on a platinum-gold foil and the glass-water slurry is applied over the external surface of the porous substructure.

• The infiltration firing is performed for 4 to 6 hours at 11000 C (in the In-Ceramat furnace).The glass infiltrate melts at 800°C


• At 1100°C the molten glass diffuses through the interstitial spaces of the porous alumina core by capillary action and encapsulates the fine grain alumina particles.

• This infiltration firing increases the strength of the core to about 20 times its original strength.

• The plaster (gypsum die) shrinks during sintering so the glass-infiltrated coping can be easily removed from the die


DUPLICATION

IN-CERAM REFRACTORY DIES IN-CERAM APPLICATION

WORKING MODEL

AL2O3 SLIP {10 HRS 1120 0C- 2HRS}

VITA INCERAMAT

SHRINKAGE OF DIES GLASS INFILTRATION 4HRS 11000C

APPLICATION OF BODY AND INCISAL

PORCELAIN

POSTOPERATIVE VEIW OF IN-CERAM CROWNS

FINISHED IN-CERAM COPINGS

FINISHED CROWNS

PREOPERATIVE VEIW

• PROPERTIES

• STRENGTH :

The densely packed crystalline particles (70% alumina)

Limit crack propagation and prevent fracture.

Studies have shown that though the compressive strength of In-Ceram lies between that of IPS Empress Pressable glass-ceramic and metal-ceramic restorations, its fracture resistance did not differ significantly from the metal-ceramic restorations. (Giordono et al,1995)

• COLOR :

The final color of the In-Ceram restorations is generally influenced by the color of the alumina core, which tends to be opaque.

In spinell variety, the core is more transparent

• USES:

• Single anterior & posterior crowns

• Anterior 3-unit FPD's

ADVANTAGES• Optimum aesthetics and excellent biocompatibility.

• Withstands high functional stress due to excellent physical values

• No thermal irritations on account of low thermal conductivity

• Offers the possibility of non-adhesive seating

• Radiolucent

• High degree of acceptance among the patients

INDICATIONS-

- Single crowns

- 3 unit anterior bridges

Contraindications:-

• Insufficient hard tooth substance available

• Inadequate preparation results

• Bruxism

In ceram spinell• Magnesium spinell (MgAl2O4) as the major crystalline phase

with traces of alpha-alumina, which improves the translucency of the final restoration.

• Final core material – Glass infiltrated magnesium spinell

Advantages

• Spinell has extended uses(Inlay / Onlay, ceramic core material and even Veneers.)

Disadvantage

• 25% reduction in strength

• Incapable of being etched by hydrofluoric acid.

In ceram zirconia• Contains tetragonal zirconia and alumina as the major

crystalline phase.

• Final core material – 30%wt Zirconia + 70%wt Alumina

• Advantage

• High flexural strength ( 1.4 times the stability as the ln-Ceram Alumina)

• Excellent Marginal Accuracy

• Biocompatibility.

• Disadvantage :

• Poor esthetics due to increased opacity.

350 MPa 500 MPa 700 MPa

In-ceram Alumina In-ceram Spinell

In-ceram Zirconia

Flexural strength

In ceram sprint

ʺ The time saving system ʺ

Vita In ceram sprint provides rapid production of alumina crown copings .

The furnace firing time has been dramatically reduced compared with conventional firing methods

MACHINABLE CERAMICS

MACHINING SYSTEM

CAD-CAM(DIGITAL) COPYING SYSTEMS

(ANALOGOUS)

DIRECT

•Cerec 1

•Cerec 2

INDIRECT

•Automill

•Denti CAD

COPY MILLING EROSION

1.MANUAL 1.SONOEROSION Celay DFE Erosonic

2.AUTOMATIC 2.SPARK EROSION Ceramatic DFE Procera

CAD-CAM Ceramics

• 　 In dentistry, the major developments of dental CAD/CAM systems occurred in the 1980s. There were three pioneers in particular who contributed to the development of the current dental CAD/CAMsystems.

• Dr. Duret contributed in the field of dental CAD/CAM development.

• Dr. Moermann, the developer of the CEREC® system3.

• Dr. Andersson, the developer of the Procera. Dental material journal 2009,28,44-45

• Uses digital information about the tooth preparation or a pattern of the restoration to provide a computer-aided design (CAD) on the video monitor for inspection and modification.

• The image is the reference for designing a restoration on the video monitor.

• Once the 3-D image for the restoration design is accepted, the computer translates the image into a set of instructions to guide a milling tool (computer-assisted manufacturing [CAM]) in cutting the restoration from a block of material.

Advantages

• Negligible porosity levels in the CAD-CAM core ceramics.

• Freedom from making an impression.

• Reduced assistant time associated with impression procedures

• Need for only a single patient appointment (with the Cerec system), and good patient acceptance.

Disadvantages

• Need for costly equipment.

• The lack of computer-controlled processing support for occlusal adjustment

• The technique sensitive nature of surface imaging required for the prepared teeth.

Dental material journal 2009,28,44-45

BASIC WORKING PRINCIPLE OF CAD CAM SYSTEM

COMPUTER AIDED DESIGN & COMPUTER AIDED MANUFACTURING

CAD/ CAM Systems exhibit three computer linked functional components

• 1. Computerized surface digitization

• 2. Computer - aided design

• 3. Computer - assisted manufacturing

Gary Davidowitz The Use of CAD/CAM in Dentistry,Dental Clinics, Vol. 55, Issue 3, p559–570

STEP 1 - OBTAINING AN OPTICAL IMPRESSION

• Data from the patient i.e. tooth and soft tissue, or master cast or impression is captured electronically with the aid of -

1.INTRAORAL SPECIALIZED CAMERA OR

2.LASER SYSTEM OR

3.MINIATURE CONTACT DIGITIZER OR

4.SAPPHIRE PROBE

Gary Davidowitz The Use of CAD/CAM in Dentistry,Dental Clinics, Vol. 55, Issue 3, p559–570

STEP 2 – RESTORATION DESIGN

• Data thus acquired is now analyzed using CAD software provides a 3 – Dimensional image of future restoration

• A 3 – Dimensional image of future restoration is produced which is analyzed in all planes to avoid any variations with original structure.

• Using the CAD software an Occlussal Analysis is made, any undercuts are marked and digital image is sent to clinician for correction

STEP 3 - RESTORATION PRODUCTION

• Restoration is then produced by

1. Machining with computer controlled milling machines

2. Electric discharge machining

THE CEREC SYSTEM

• CEREC concept was given in 1980 by W. Moermann and M. Brandestini and developed by Siemens.

• The term was selected for the CAD/ CAM machine from the words “CEramic REConstruction”

• CEREC I was restricted to Inlays, Onlays and Veneers

CEREC - I

Dental CAD/CAM systems: A 20-year success story. E. Dianne Rekow . J Am Dent Assoc 2006;137;5S-6S

• STEP I – POWDER APPLICATION

• Optical Characteristics of Enamel and Dentin prevent cavity preparations from being three dimensionally scanned.

• A layer of CEREC powder is applied to make the tooth surface opaque and non – reflective.

• Powder is inert and removed with a simple air – water spray

• A green powder( TiO2 )wet can spray was introduced to produce even deposition of powder.

STEP II – OBTAINING THE OPTICAL IMPRESSION

• A small hand held video camera with a 1 cm wide lens is placed close to the occlusal surface

• Thus, image is digitized and the vertical dimension ( depth of cavity ) is measured by shift in incident and reflected light i.e. deeper parts show more shift

• STEP III – ANALYSIS OF IMAGE

A “reverse mouse” is used and the cursor is first placed on gingival margin against buccal wall and moved along all internal line angles.

• Two main types of ceramic are used

1. Conventional Porcelain containing quartz in a feldspathic porcelain block VITA and CERAMCO

2. Porcelain without Quartz DICOR

Porcelain block is mounted on a metal stub which is then loaded on milling unit.

Entire milling operation takes 4 – 6 minutes.

Milling is done by means of a diamond covered disk in conjunction with high velocity air – water spray.

STEP IV – MILLING OF THE CERAMIC RESTORATION

DIAMOND COATED MILLING DISC

MILLING IN PROGRESS – Synchronous movement

of grinding wheel and bur

• The image further shows the percentage of milling process that is completed

• A continuous read out also comes showing the efficiency of diamond wheel and probable need for replacement

Stages representing Milling of the Restoration from The block

ADVANTAGES 1. Natural Esthetics

2. Optimal Cutting and Quality of Material ensure an accurate restoration

3. Glazing is not required

4. Minimal abrasion of hard tissues as restorations are fabricated meeting occlusal demands

5. High stability during various occlusal excursive movements

6 High patient acceptance as restoration can be provided to patient chair side

7. Cost of Porcelain used is equal to Composite resin as minimal material is used.

8. Conventional Impression steps and preparation of models avoided thus laboratory processing time is reduced.

DISADVANTAGES

1. Complicated Software

2. Limited Color identification range

3. Costly investment

4. Very bulky and requires expertise to master the functioning.

Clinical shortcoming of Cerec 1 system:

• Although the CEREC system generated all internal and external aspects of the restoration, the occlusal anatomy had to be developed by the clinician using a flame-shaped, fine-particle diamond instrument and conventional porcelain polishing procedures were required to finalize the restoration.

• Inaccuracy of fit or large interfacial gaps.

• Clinical fracture related to insufficient depth of preparation.

• Relatively poor esthetics due to the uniform colour and lack of characterization in the materials used.

Developed by Moermann and Brandestini

Introduced in September 1994, and is the result of constant further development via different generations of Cerec units to eliminate the previous limitations.

The major changes include :

Enlargement of the grinding unit from 3 axis to 6 axis.

Upgrading of the software with more sophisticated

Cerec 2 system

• Data representation in the image memory and processing increased by 8 times

• Magnification factor increased from x8 to x12 for improved accuracy during measurements.

• Monitor can be swiveled and tilted, thus facilitating visual control of the video image.

Other technical innovations of Cerec 2 compared to Cerec 1:

• The improved Cerec 2 camera : new design, easy to handle, a detachable cover (asepsis), reduction in the pixel

CEREC 3D

• CEREC 3D is an acronym for Chairside Economical Restoration of Esthetic Ceramics

• Introduced in January, 2000 and after one year of Clinical use and studies it was introduced in 2001

• Cerec 3D uses CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) 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.

• The whole process takes about one hour.

Computer monitor

Function switches

Base containing pump unit and water supply

Storage drawers

Optical impression

Tracker ball

Milling unit

• Dr. Stefan Eidenbenz, University of Zurich, developed this 8 axis milling machine called CELAY in 1990.

• It has two main features:

1. A Hand Operated contacting probe that traces the external contours of an acrylic or wax inlay, fabricated in mouth.

2. A milling arm, follows the probe by means of a pantographic arm, with 8 degrees of freedom, thus cuts the copy of a “Pro Inlay (wax or acrylic pattern)” from a porcelain block.

• CELAY employs no computer; a direct copy milled restoration is obtained.

THE CELAY SYSTEM

• There are four main steps in this procedure:• Fabrication of a PRO – INLAY• Copy Milling• Insertion• Finishing.

The Scanning deviceScanning a wax pattern

The Milling devicecuts a porcelain

block

WAX Pattern for Crown

Coarse diamond points used for initial processing of porcelain

FINISHING OF PORCELAIN COPING WITH 64 MICRONS DIAMOND POINT

FINISHED CROWNS

Cercon

• The Cercon Zirconia system (Dentsply Ceramco, Burlington, NJ) consists of the following procedures for production of zirconia-based prostheses.

PROCERA ALL CERAM SYSTEM(Nobel Biocare)• PROCERA system was introduced in 1986.

• Initially it was used to fabricate crowns and FPDs by combining a Titanium substructure with a low fusing veneering porcelain.

• Later in 1993 it was used to produce All ceramic crowns.

• The crown is composed of a densely sintered, high purity aluminium oxide coping that is combined with a low fusing veneering porcelain.

PROCEDURE

• Procera® Piccolo• enables single

tooth scanning for crowns, laminates and abutments.

Procera® Forte scan crowns,

laminates and abutments as well as bridges.

• Sapphire ball forms the tip of the scanner.

• Extremely light pressure of approx 20g maintains the probe in contact with the die

• Within 3 mins , more than 50,000 data points are gathered , defining the three dimensional shape of the die .

• Next step in designing is to establish the thickness of the coping to be fabricated.

• Relief space for the luting agent is automatically established by computer algorithm .

• Sintering shrinkage of 20% is taken into account , so enlarge model of the preparation is made with the help of the CAD-CAM technique .

• High purity aluminum oxide powder is compacted against the enlarged die

• The outer surface is milled and the coping is sintered to full density .

• Then veneering porcelain is added

Lava all ceramic system

Consists of a non contact optical scan system , a pc with monitor and the LAVA CAD Windows based software which displays the model as three dimensional object.

LAVA Milling unit

This computer controlled precision milling unit can mill out 21 copings or bridge frameworks without supervision or manual intervention

LAVA therm

Bridges and crown frameworks undergo sintering and exact dimensions ,density and final strength in the high temperature LAVA therm furnace

Lava™ Plus

• Based on a unique 3M™ ESPE™ shading technology

• This unique technology used in the lava™ premium dyeing liquids also helps to preserve translucency after shading, without compromising strength.

Lava™ Ultimate

• A resin nano ceramic-a new class of CAD/CAM material with unique functionality having an elastic modulus that is comparable to dentin

Features of the YTZP blanks :

They are pre sintered

The shade of the core material can also be stained resulting in the ability to control the shading of the restoration.

The core is translucent in comparison with other zirconia based ceramic core systems .

Other systems

Sopha ( designed by DURET )

DentiCAD(BEGO ,Germany and DentiCAD ,USA)

DCS-PRESIDENT

Introduced in 1990 by DCS production Switzerland

DC Zirkon blocks (Y-TZP) blocks from which crown and core copings are milled are fully sintered

However it is said that the white colored, opaque core material may limit the esthetic quality of the restoration .

Procedure

A conventional wax model is digitized with preciscan laser scanner

The precimill machining center mills the substructure from from fully sintered DC Zircon Blank .

CERAMIC INSERTS

• Eg: Cirona

• Pressed leucite inlay

• Etched with HF and silanised, with a shelf-life of over five years, before being sealed into a sterile blister pack

Indications

• Class I, II (conventional and tunnel design), III, and IV cavities

• Closure of endodontic access cavitiesB J Millar Primary Dental Care: Journal of the Faculty of General Dental Practitioners (UK) 1999, 6 (2): 59-62

• Size-matched cerana burs

• The cavity is refined using one of three conical burs

• Size- and shaped-matched conical inlay is cemented using a conventional restorative resin material

• The final restoration consists of a leucite inlay surrounded by a small amount of composite resin.

• The exposed resin, has a higher filler loading than that of a luting cement

B J Millar Primary Dental Care: Journal of the Faculty of General Dental Practitioners (UK) 1999, 6 (2): 59-62

Restoration of a Class II cavity

http://www.nature.com/bdj/journal/v201/n8/fig_tab/4814159a_F2.html

http://www.nature.com/bdj/journal/v201/n8/fig_tab/4814159a_F2.html

DOUBLE INLAY• Hannig and schmeise

• Proximal boxes extending into dentine are restored with a conventionally cemented metal base and then covered with a porcelain inlay having margins confined to enamel

• Indications

• Proximal cavities in deeply damaged molars and premolars with margins extending into the root dentin

• Advantages

• Cast restoration at the critical cervico proximal cavity margins

• The esthetic and stabilizing properties of the adhesively bonded restoration technique in visible areasDailey B1 The double-inlay technique: a new concept and improvement in design, J Prosthet Dent.2001 Jun;85(6):624-7

Natural inlays

• 'Recycling' of extracted teeth for the production of dental restorations.

• Using the celay milling machine

• Two pairs of matching sound extracted permanent molar teeth were used

• The molars were matched for mesio-distal size of the tooth crown and the convexity of the proximal surfaces

• One tooth of each pair was assigned to be the 'donor' tooth, the other tooth being the 'host‘.

• Mo inlay preparations were made in the host teethMoscovich H, Creugers NH The novel use of extracted teeth as a dental restorative material, J Dent.1998 Jan;26(1):21-4.

Spark Erosion

• It refers to 'Electrical Discharge Machining' (EDM.

• It may be defined as a metal removal process using a series of sparks to erode material from a work piece in a liquid medium under carefully controlled conditions.

• The liquid medium usually, is a light oil called the ‘dielectric fluid’. It functions as an insulator, a conductor and a coolant and flushes away the particles of metal generated by the sparks.

Sono erosion• Based on ultrasonic methods.

• First, metallic negative moulds (so-called sonotrodes) are produced of the desired restoration, both from the occlusal as well as from the basal direction.

• Both sonotrodes fitting exactly together in the equational plane of the intended restoration are guided onto a ceramic blank after connecting to an ultrasonic generator, under slight pressure.

• The ceramic blank is surrounded by an abrasive suspension of hard particles, such as boron carbide, which are accelerated by ultrasonics, and thus erode the restoration out of the ceramic blank

PANAVIA SA CEMENT

• KURARAY CO,LTD, Japan

• is a self-adhesive; self-etch; fluoride-releasing dual-cure resin cement available in both automix and handmix version.

• Cementation of crowns, bridges, inlays and onlays made of conventional porcelain, ceramic, hybrid ceramics, composite resin or metal Cementation of metal cores, resin cores, metal posts or glass-fiber posts

Invisible Onlay• A modification of the traditional onlay preparation to minimize

gold display on the occlusal buccal of upper bicuspids and molar.

• lingual cusp needs to have adequate strength to resist the occlusal forces

• Helps prevent cusp fracture and relief sensitivity when tiny fractures are present.

Review of literature

Pröbster L, Int J Prosthodont 1993 May-Jun;6(3):259-63.

• This paper reports on 76 consecutively placed In-Ceram restorations (61 complete-coverage crowns and 15 fixed partial dentures)

• During the 35-month observation period no crown failures occurred, a five-unit fixed partial denture fractured, and another fixed partial denture was removed because of periodontal complications.

• Thus, In-Ceram complete-coverage ceramic crowns are apparently indicated for anterior and posterior teeth. A larger number of subjects must be studied to assess the indication for all-ceramic fixed partial dentures

Haselton DR, Diaz-Arnold AM, Hillis SLJ Prosthet Dent 2000 Apr;83(4):396-401• Forty-one patients (16 men, 25 women; mean age 47.3

years, range 18 to 77 years) were examined with a total of 80 In-Ceram all-ceramic crowns fabricated at the University of Iowa College of Dentistry from 1994 to 1997.

• The percentage distribution for crowns included: 67% anterior single crowns, 26% posterior single crowns, 6% anterior implant crowns, and 1% posterior implant crowns

• The estimated 4-year success rates : 83.5% (65.7%-94.6%) for marginal integrity, 95.8% (82.9%-99.8%) for shade match, and 95.5% (81.6%-99.7%) for secondary caries, 100% (88%-100%) for wear, and 100% (88%-100%) for cracks.

Odén A, Andersson M, Krystek-Ondracek I, Magnusson D, J Prosthet Dent. 1998 Oct;80(4):450-6.

• Evaluated the clinical performance of 100 Procera AllCeram crowns after 5 years in service.

• One hundred Procera AllCeram crowns were fabricated for 58 patients (20 men and 38 women). Patients were treated by 4 general dental practitioners.

• Of the 97 crowns remaining in the study after 5 years, only 3 crowns had experienced a fracture through the veneering porcelain and the aluminum oxide coping material. Two additional crowns were replaced as a result of fractures of only the veneering porcelain. One crown was replaced as a result of recurrent caries

Kussell A. Giordano et al ( JPD 1995:73;411-418)

• In their study determined the flexural strength of In-Ceram system components and compared the core material with conventional feldspathic ceramics and with Dicor all-ceramic restorative material.

1. The flexural strength of In-Ceram ceramic core (236.15 ± 21.94 MPa) material was more tha twice that of polished Dicor ceramic (107.78±8.45 MPa) and feld-spathic porcelain(69.74 ± 5.47 MPa).

2. Glass infusion of alumina elevated the flexural strength of InCeram alumina matrix from 18 MPa to 236Mpa.

CONCLUSION

Each system has its own merits, but may also have shortcomings. Combinations of materials and techniques are beginning to emerge which aim to exploit the best features of each.

It is no exaggeration to state that the last century saw a revolution in dental esthetics and is expected to continue, which will be influential in determining the range of ceramic products made available

QUESTIONS

1. ANSWER IN DETAIL: [100 MARKS]

CERAMICS IN RESTORATIVE DENTISTRY (RGUHS MAY 2010, MAY 2007)

SHORT ESSAY 2. CAD CAM (NITTE APRIL 2013, RGUHS MAY 2010)3. ALL CERAMIC SYSTEMS IN RESTORATIVE DENTISTRY4. ALUMINOUS PORCELAIN (RGUHS NOV2011)5. CERAMIC INSERTS(APRIL 2008)

References Phillips science of dental material --- Anusavice, XI edition Restorative dental material—Craig,Powers XI edition Art and science of dental ceramic---John Mclean. Applied dental materials – Mc Cabe John F Rosenblum MA, Schulman A. A review of all ceramic restorations J

Am Dent Assoc. 1997;128:297–307 Dental ceramics current thinking and trends –Kelly JR, Dent clin

of N America 2004;48:513-518 Symposium on Ceramics –O’Brien WJ- Dent Clin of N America

1985;29(4) 621 Dental Clinics of North America; 51(2007) 713-727; Recent

Advances in Materials for All-Ceramic Restorations Denry IL.Recent advances in ceramics for dentistry.Crit.Rev Oral

Bio Med.1996;7(2)134-143 J Prosthet Dent 2007;98:389-404; Current ceramic materials and

systems with clinical recommendations: A systematic review Cast glass ceramics. Dent Clin North Am. 1985 ; 29(4): 725-39. A comparative study of the strength of aluminous porcelain and all-

ceramic crowns. J Prosthetic Dent 1989; 61: 297-304 Dental Materials 2008;24; 299-307 : State of the art of zirconia for

dental applications. Scotti R, Catapano S, D‘Elia A. A clinical evaluation of In-Ceram

crowns. Int J Prosthodont. 1995;8:320–3 Strength of Magnesia-core crowns with different body porcelains.

Int J Prosthodontics 1993- 6: 60-64• Dental CAD/CAM systems: A 20-year success story. E. Dianne

Rekow . J Am Dent Assoc 2006;137;5S-6S • Materials for Chair side CAD/ CAM produced restorations. Giordano

R. JADA 2006; 1337; 14S-21S

METAL FREE CERAMICS- AN UPDATE

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