Metal Free Ceramics / orthodontic courses by Indian dental academy

METAL FREE CERAMICS INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

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INTRODUCTION

• Of all materials used in dentistry to restore the natural dentition, ceramics have by far the best optical properties to mimic tooth structure in appearance translucency, light transmission and biocompactibility give dental ceramics highly desirable esthetic properties.

All ceramic inlays,onlays,veneers and crowns are some of the most esthetically pleasing prosthodontic restoration. Because there is no metal to block light transmission, they resemble natural tooth structure better in terms of color and translucency than any other restorative option.

DEFINITION

• ACCORDING TO GPT 1999: • CERAMIC IS DEFINED AS:• Compound of one or more metal with a

nonmetallic element, usually oxygen.They are formed of chemical and biochemical stable substances that are strong, hard,brittle and inert non conductors of thermal and electrical energy.

PORCELAIN

• Is defined as a ceramic material formed of infusible elements joined by lower fusing material.

• Most dental porcelain are glasses and used in fabrication of teeth for dentures, pontics, metal ceramic restoration ,crowns and other restoration.

COURTESY:ANUSAVICE

• CERAMIC is a compound of metallic and nonmetallic elements.

• Metals:Aluminium, Calcium, Lithium, Magnesium, Potassium, Sodium, Tin, Titanium,Zirconium.

• Nonmetals:Silicon, Boron, Fluoride, Oxygen.

• They may be used as a single structural component .e.g:CAD CAM inlay

• Or as one of the several layers.e.g: Fabrication of ceramic based prosthesis.

• ALL PORCELAIN AND GLASS- CERAMICS ARE CERAMIC ,BUT NOT ALL CERAMICS ARE PORCELAINS OR GLASS CERAMICS.

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CONTINUED….• They are formulated to provide one or more of the

following properties:• 1.CASTABILITY 6.COLOR• 2.MOLDABILITY 7.MACHINABILITY• 3.INJECTABILITY 8.ABRASION RESISTANCE• 4.TRANSLUCENCY 9.STRENGTH • 5.OPACITY 10.TOUGHNESS•

HISTORY OF DENTAL CERAMICS

• Dental technology existed in ETRURIA as early as 700 BC and during Roman 1st century BC but remained undeveloped until 18th century.

• Material used for artificial teeth in 18th century is• 1.Human Teeth.• 2.Animal teeth carved to the size &shape• of human teeth. 3.Ivory.• 4.Mineral or porcelain teeth.

Continued…

• DISADVANTAGE:• 1.Human teeth-costly& scarce• 2.Animal teeth-unstable

towards the corrosive agents in saliva• 3.ivory&bone- contains pores &

are easily stained.

Continued…

Mineral teeth or porcelain dentures greatly accelerated as an end to the usage of human and animal teeth.

Feldspathic dental porcelain were adapted from European triaxial white ware formulations( clay- quartz- feldspar).

Continued…

• After decades of effort, Europeans mastered the manufacture of transluenct porcelain, comparable to the porcelain of chinese by 1720.

The use of feldspar to replace lime & high firing temperature are the both critical developments.

Continued…

• 1723,Enameling of denture metal bases was described by PIERRE FAUCHARD in LE CHIRURGIEN DENTISLE. He was credited with recognizing the potential of porcelain enamels and initiating research with porcelain to imitate color of teeth & gingival tissues.

Continued…

• 1774, a parsian apothecary ALEXIS DUCHATEAU with assistance of parisian dentist NICHOLAS DUBOIS DE CHEMANT continually improved porcelain formulations.

In England DUDOIS DE CHEMANT procured supplies from collobration with JOSIAH WEDGWOOD.

Continued…

• 1808, GIUSEPPANGELO FONZI of paris introduced individually formed porcelain teeth that contained embedded platium pins known as TERRO-METALLIC IN- CORRUPTIBLES and their esthetic &mechanical versatility provided major advance in prosthetic dentistry.

Continued…

• Improvement in transluency&color of dental porcelains were realised through developments that ranged from formulations of ELIAS WILDMAN in 1838 to vaccum firing in 1949

Continued…

• Glass inlays(not porcelain)were introduced by HERBST in 1882 with crushed glass frit fired molds made of plaster&asbestos.

Continued…

• In 1885 LOGAN resolved the retention problem encountered between porcelain crowns&post that were commonly made of wood by fusing the porcelain to platinum post-RICHMOND CROWN.

• These crowns represent the first innovative use of metal ceramic system

Continued…

• In 1886, combining burnished platinum foil as a sub structure with the high controlled heat of a gas furnance,LAND introduced first fused feldspathic porcelain inlays&crowns.

• All porcelain crown system despite of its esthetic advantages failed to gain widespread development until alumina was used as reinforcing paste.

Continued…

• A noteworthy development occurred in 1950 with addition of leucite to porcelain formulation that elevated the coefficient of thermal expansion to allow fusion to certain gold alloys to form complete crowns and FPD.

• Refinements in metal ceramic systems dominated dental ceramic research during the 35years that resulted in improved alloys,porcelain metal bonding and porcelain.

Continued…

• In 1965 McLEAN&HUGHES developed a PJC with a inner core of aluminous porcelain containing 40% to 50% alumina crystals to block the propagation of cracks.

• The inner core is layered with conventional porcelain resulting in a restoration approx twice as strong as traditional PJC.But the structure is still insufficient for anything but anterior crowns.

Continued…

• Fracture resistance of the aluminous PJC was improved by a technique in which the platinum matrix is left in completed restoration.

• The platinum foil decreased the amount of light transmitted which diminishes somewhat esthetic advantage of all ceramic.

Continued…

• The introduction of a “shrink-free”all ceramic crown system(cerestore,coors biomedical)& castable glass ceramic crown system(dicor,dentsply) in 1980s provided additional flexibility for achieving esthetic results.

• Advanced ceramic systems introduced with innovative processing methods stimulated renewed interest in all ceramic prosthesis.

DEFINITION

• ACCORDING TO GPT 1999, • ALL CERAMIC is defined as ceramic

restoration that restores a clinical crown without a supporting metal substructure.

COURTESY:ANUSAVICE

• PJC: • One of the first types of all ceramic

crown made from a low strength aluminous core porcelain & veneering porcelain(with matching thermal contraction coefficient) without the use of a supporting metal substrate except in some instances for a thin platinum foil.

• CJC:• An all ceramic crown without a supporting

metal substrate that is made from a ceramic with a substantial crystal content(>50 vol%)from which its higher strength and/or toughness is derived.These crowns are distinguished from PJC that are made with low strength core material,usually aluminous porcelain or feldspathic porcelain.

DISADVANTAGES OF METAL CERAMICS

• Metal margin exposure • To achieve better esthetics,the facial margin

of an anterior restoration is often placed subgingivally which increases the potential for periodontal diseases.

• Risk of over contouring-metal 0.5mm and the rest is ceramic material.

• Because of glass like nature of veneering material they are subjected to brittle fracture.

• Metal bases affect the esthetics of porcelain by decreasing the light transmission through the restoration and by creating metal ion discoloration.

• Fit of long span bridges may be affected by the creep of the metal during successive bakes of porcelain.

• Porcelain made in metal ceramic technique are more liable to devitrify which can produce cloudiness.

• Some patients have allergic reaction or other sensitives to metal.

• These drawbacks have prompted the development of new all ceramic system that do not require metal,yet have high strength and precission fit of cerametal system.

STRENGTH

• Strength is greatly influenced by presence of surface flaws acting as stress initiators&causing widening&propagation of micro cracks through material from the surface.Therefore dental porcelain is much weaker in tension than in compressive and is prone to brittle fracture.

• Strength is influenced by static fatigue which is generally caused by a stress dependent chemical reaction between water vapour &surface flaw in the restoration.This causes flaw to grow to critical dimension,allowing spontaneous crack propagation, resulting in a fracture with comparatively little occlusal loading particularly over long periods.

CLASSIFICATION OF DENTAL CERAMICS

• COURTESY:ANUSAVICE• Dental ceramics are classified according to • 1.Types• 2.Uses • 3.Processing methods• 4.By substructure material

1.Feldspathic porcelain 2.Leucite reinforced porcelain3.Aluminous porcelain4.Alumina5.Glass infiltrated alumina 6.Glass infiltrated spinel7.Glass ceramic

• Denture teeth • Metal ceramics• Veneers• Inlays• Crowns • Anterior bridges

PROCESSING METHODS

• 1.Sintering• 2.Casting• 3.Machining

SUBSTRUCTURE MATERIAL

• 1.Cast metal • 2.Swaged metal• 3.Glass ceramic• 4.CAD CAM porcelain• 5.Sintered ceramic core

COURTESY:SHILLINGBURG

• According to firing temperature:• High fusing:-1,290-1,370 C(2,350-

2,500F)• Medium fusing:-1,090-1,260 C(2,000-

2,300F)• Low fusing :-870-1,065C(1,600-

1,980F)s

HIGH FUSING PORCELAIN

• Is used for manufacture of porcelain teeth,also for some extent for PJC.

• Composition:• FELDSPAR-70% to 90%-matrix• QUARTZ-11% to 18 %-refractory

skeleton.• KAOLIN-1% to 10%-acts as a binder when

porcelain is ‘green’ or unfired.

LOW AND MEDIUM FUSING PORCELAIN

• Manufactured by a process called fritting.• Raw constituents of porcelain are

fused,quenched&ground back to an extremely fine powder.

INTEREST FOR ALL CERAMIC CROWNS

• It has more potential for more esthetic anterior restoration.

• In PFM,alloys structure produces opaque appearance and metal margin are often visible.

• Selection of alloys for PFM is confusing issue.

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• High gold content alloys are relatively expensive.

• Risk of metal allergy, bond failure,porcelain discoloration

GENERAL CLASSIFICATION

• Powder slurry/sintered porcelain.• Castable ceramics.• Pressable ceramics.• Infiltrated glass ceramic.• Machinable ceramic.

POWDER SLURRY PORCELAINS

• Products are supplied as powder to which ceramist adds distilled water to produce a slurry,which is build up in layers on a die material to form the contours of restoration.The powder is available in different shades and translucencies and are supplied with characterstics stains and glazes.

EXAMPLES

• OPTEC H.S.P(JENERIC/PENTRON)• DUCERAM L.F.C(DUCERA INC)• VITA HI-CERAM(VITA ZAHNFABRIK)

OPTEC H.S.P(HIGH STRENGTH PORCELAIN)

• Leucite reinforced feldspathic porcelain• The manufacturer disperses the leucite

crystals in a glassy matrix by controlling their nucleation and crystal growth during the initial production of porcelain powder.

• The leucite crystals added to the glass base are 10microns in size and its concentration is 50 to 60 wt%.

Body and incisal porcelain are pigmented to provide desired shade&translucency.

• Greater strength so no core required.• Leucite and glass matrix fused at 1020

deg C.

ADVANTAGES

• 1. Lack of metal or opaque substructure.• 2.Good transluency.• 3.Moderate flexural strength.• 4.No special laboratory equipment needed.•

• 5.Two and a half times stronger than conventional porcelains.

• 6.It transmits,reflects&refracts light in the same manner as natural teeth ideal for laminate veneers.

DISADVANTAGES

• Porcelain margin inaccuracies caused by porcelain sintering shrinkage.

• Potential to fracture in posterior teeth.• Increased leucite content leads to in vitro

wear of opposing teeth.

DUCERAM L.F.C

• Composition: amorphous glass containing hydroxyl ions.

• Manufacturer claims that this noncrystalline structure has greater density,higher flexural strength,greater fracture resistance and lower hardness than feldspathic porcelain.

• High flexural strength results from an ion exchange mechanism of hydroxyl ions which is said to also promote a healing of surface micro cracks.

• Decreased hardness is due to absence of leucite crystals.

PROPERTIES

• Flexural strength-110 Mpa• Hardness close to natural teeth due to

absence of leucite.• Opalescence of natural teeth can be

reproduced.• Fluorescence is very close to natural teeth.

ADVANTAGES

• Excellent marginal adaptation.• No special equipment required.• Allow modification by repeated firing.• Abrasion rate close to that of natural teeth.• Good esthetic results.

INDICATION

• Ceramic inlays.• Veneers.• Full contour crowns.

CONTRA INDICATION

• Masking grossly discolored teeth.• When aiming for high fracture resistance.

VITA HICERAM

• MATERIAL:• Higher content of aluminium

oxide/aluminium oxide reinforced.• It consists of 50% of aluminium crystals in a

matrix of low fusing glass of matching thermal expansion.

• Aluminous core porcelain are twice stronger than regular porcelain.

MERITS

• Highly accurate margins.• Higher melting points and greater stability.• For both anterior and posterior crown

veneers.

CASTABLE CERAMICS

• These products are supplied as solid ceramic ingots which are used for fabrication of restorations using lost wax and centrifugal casting technique.The restoration is either covered by conventional feldspathic porcelain or is stained to obtain proper shading and characterisation of final restoration.

• EXAMPLE:• Dicor(corning glass,Dentsply)-

micaceous glass ceramic.• Dicor plus-Dicor coping with compatible

veneering porcelain.• Cerapearl(Bioceram,Kyocera)-

Hydroxyapatite is a main crystalline phase.

• Dicor castable glass ceramic is one of the pyoceram ceramics manufactured by STOOKEY of the corning glassware in 1978.

• Dicor is the first commercially available castable ceramic material for dental use.

• Present system was introduced by PETER ADAIR and DAVID GROSSMAN in 1984.

• It is a composite materials of a glassy matrix phase and a crystal phase

COMPOSITION

• SiO2-45%-70%w/w• K2O-20%w/w• MgO-3%-13%w/w• MgF2-4%-9%• Fluoride acts as a nucleating agent which aids

the growth of crystalline phase leading to growth of 0.5-2 microns small tetrasilicic crystals and it improves fluidity of molten glass.

• Al2O3 and ZrO2-minor amounts-incorporated for durability and fluorescing agent for esthetics.

MATERIAL

• Dicor restoration is made by investing a wax pattern and casting by last wax process.

• Cast crown is a clear glass that must be heat treated to form a crystalline phase composed of tetrasilicic fluoromica(K2Mg5SiO8O20F4) which provides fracture resistance and strength(Hoekstra 1986).

• Crystallisation procedure takes place during heating the reinvested crown for 6hrs at 1070 C – causes the growth of microscopic plate like crystals of crysyalline material(mica)in the glass matrix.

• This crystal nucleation and crystal growth is known as ceramming.

• It forms 45 vol %-glass matrix, 55 vol %-tetrasilica fluoro mica crystals.s

• This causes mica to form a “STRONG HOUSE OF CARDS”structure which makes fracture propagation especially equally difficult in all direction.

• It is highly transluescent.

CREATION OF CAST GLASS CERAMIC RESTORATION

• Full anatomic wax up.

• Casting to a glassy state.

• Ceramming to a crystalline glass ceramic.

• Applying external colorants.

SURFACE REACTION

• Between investment material&glass leads to an exchange of ions between the two as a result of high temperature&long reaction time.

• Glass releases potassium ions(k ions)&takes up a calcium ions . It loses fl ions from its surface.

• This leads to a composition at the glass surface that is different from internal composition of the glasses.

• The outer skin layer on dicor ceramic contains needle like crystals of the silicate enstatite(MgSiO3) oriented perpendicular to the surface –ceram layer and is the site of considerable residual porosity.

• This weakend surface layer reduces the significantly the overall strength of the material.

• Characterisation of crown is achieved by surface glaze.

PROPERTIES

• 1.Strength:-Crystalline structure of this material lessens the likelihood of crack propagation because the lattice structure is able to absorb compressive forces.

• 2.Abrasiveness:-The hardness coefficient& wear characteristic is as same as enamel.

• Cast ceramic-362KHN• Enamel-343 KHN

• 3.Light absorptive refraction:-• Glass ceramics refracts 75% of

entity light because of its organised crystalline structure which a refractive index similar to that of enamel which guides the light deep into the ceram.

• It absorbs light from other teeth& filling material creating a “Chameleon effect”.

• Cast glass ceramic are radiolucent & allow radiographic examination of marginal integrity,extreme thickness of bases & podt & cores.

• 4.Compactibility:-• It exhibition less surface plaque

accumulation than enamel , cementum & any other restoration material.

• fluoride content inhibition bacterial colonisation.

• 5.Marginal adaptation:-• More consisten in terms of fit than

gold crowns(Malament&Grossman 1992).• Thermal expansion of cast glass ceramic is

close to that of natural enamel.This causes similar expansion & contraction during normal temperature fluctuation,thus maintaining a good marginal seal.

• 6.Thermal conductivity:-• Low thermal conductivity.

ADVANTAGES

• 1.Last wax-Casting fabrication procedure/technique allow to easy morphology control.

• 2.Fit of restoration is excellent.• 3.wearing of opposing occlusion is predicted to

less than that of conventional porcelain.• 3.Fluctural strength is greater than conventional.

• 4.Marginal porcelain opening is less when compared to McCrown.

• Dicor-30-60mm• Metal Ceramic Crown-62-65mm• 5.Glazed proximal surface are very smooth

&resistent to plaque accumulation• 6.Good esthetics & transluency.

DISADVANTAGES

• 1.Special equipment & cost.• 2.The process is technique sensitive.• 3.When colorant in surface stain, any grinding on

the restoration leads to anesthetic opaque white areas.

• 4.High failures rate in posterior region of mouth.• 5.Greater bulk in some cases decreases the

chameleon effect &esthetic results.

INDICATION

• 1.Anterior porcelain J C.• 2.Inlays , onlays ,3/4 crown.• 3.Partial veneers

CONTRA INDICATION

• 1.Clinical crown length in short-it would compromise resistance & retention of the preparation.

• 2.FPD.

DICOR PLUS CERAMIC

• Because of esthetic limitation-venering cutback Dicor coping feldaspathic porcelain was developed with intrifuging name”Willi’s Glass”.

• It provided perspective to recent introduction of Dicor plus ceramic(Dentsply international).

• It is a compactible veneering porcelain for fabricating “Willi’s Glass crowns”.

CERAPEARL(KYOCERA)

• It is CaOP2O5MgOSiO2 glass ceramic or calcium phosphate glass similar to hydroxyapatite of the enamel.

Composition

• CaOP2O5-aid in glass formalisation.It is the main ingredient to form hydroxyapatite crystals.

• MgOCaO-covers viscosity• SiO2 with P2O5-forms matrix

Properties

• 1.It melts at 1460 C & casted which has an amorphous microstructure and is reheated at 870 C for 1 hr-crystalline oxyapatite.

• 2.It is unstable & when exposed to moisture forms crystalline hydroxyapatite.

• 3.It is similar to enamel providing superior mechanical strength.

INFILTRATED GLASS CERAMIC

• These are glass infiltrated core ceramics.This involves slipcasting technique for making core and the contours of the restoration are obtained by individual layering & staining technique.

• Example: Inceram (vita zahnfabrik)• Alumina • Ziremia• Spinell

INCERAM ALUMINA

• Inceram was evolved by research by Dr.Mickael Sadoun in 1985 using alumina as core material & was manufactured & marketed by Vita Zahnfabrik,Germany.

• Inceram belongs to a class of materials known as interpenetrating phase composites.

• They contain atleast 2 phases that are interwined or extend continously from internal to external surface.

• They posess improved mechanical & physical properties compared with individual components.

• Have improved sterngth & fracture resistance because a crack must pass through alternate layers of both components.

Material

• A suspension of finely grounded material-alumina(slip) is mixed to a thin,creamy,consistency,is brushed onto the die in a method slipcasting.

• Water is removed via the capillary action of porous gypsum which packs the particles into a rigid network.Initial grain size –3microns.

• It is fired at a temperature rise of approx 20 C /min to 1120 C for 2 hrs.

• This causes approx of particles with minimal compaction and minimal shrinkage(minimal sintering) of alumina forming a porous network.

• It has chalky consistency and still easy to process.

• Lathanum alumino silicate La(Al2O3 SiO2) glass is used to infiltrate the pores by capillary action at high temperature.

• Veneered with compactabile feldspathic porcelain.

Properties

• Flexural strength:-600 Mpa.• Infused alumina core is 2.5 times stronger

than glass ceramic and feldspathic porcelain.

• Posess greater compressive strength than IPS empress but less than metal ceramic restorations.

• Fracture toughness-4.7 Mpa.

Advantages

• Lack of metal substructure.• Very high flexural strength.• Excellent fit.

Disadvantages

• Opacity of core.• Unsuitable for conventional acid etching.• Need for specialised equipment.

INCERAM ZIRCONIA

• PRINCIPLE:• Strengthening is achieved by

incorporating a crystalline material that is capable of undergoing a change in crystal structure when placed under stresess & provides higher strength.

• Material incorporated is 33% zirconia(partially stabilized zirconia).

• 1.To improve flexural strength,fracture toughness and fatigue resistance.

• 2.The energy required for transformation of PSZ is taken from energy that allows the crack to propagate.

Properties

• Flexural strength is 700MPa• Greater strength-can be used for posterior

bridges.• Moderate transluency.• Biocompactible and good tissue response.• Fracture toughness is 6.8MPa.• Refractive index of PSZ > than surrounding

glass matrix.

INCERAM SPINELL

• A second generation material based on inceram technique.

• A primary difference is a change in composition to produce a more translucent core.

• Porous core is fabricated from magnesium –alumina after sintering.It has special crystalline structure referred to as ‘SPINEL’[magnesium aluminate,MgAl2O4].

• Originally magnesium oxide and aluminium oxide were mixed in a ratio of 1:1 and transformed to spinel at temp above 1600 C.

• Porous spinel is secondarily infused with glass which produces a more translucent substructure upon which vitadur alpha is placed to form final restoration.

Properties

• Weaker but more translucent than the alumina core-recommended for esthetically challenging single unit anterior restoration.

• Flexural strength=350 Mpa.• Fracture toughness=2.7 Mpa• Acid resistant,chemical stability,low

electrical conductivity,high transluency and biocompactible.

MACHINABLE CERAMICS• These products are supplied as ingots in various shades &

are milled into desired form.These machine restorations can be stained & glazed to obtain desired characterisation.

• They are 2 types:-• 1.CADCAM-Computer aided designing computer aided

milling.• Example: CEREC(sirconia)• Ivoclar proCAD(Ivoclar)• Dicor MGC(Dentsply) • 2.Copy milling:Celay(michrono technologies)

CADCAM CERAMIC

• A machinable ceramic material formulated for the production of inlays and crowns through the use of a computer aided design,computer aided machining process.

• Eg:Cerec,cerec2,cerec3,cerec scan,cerec inlab,procera.

History

• Development of CADCAM systems for the dental profession began in

• 1970s with Duret in France,Altschuler in USA, Mormann and Brandestini in Switzerland.

• Rekow-1987• William-1987• Rekow et al-1992-93• Rice & Mecholsky-1997

Objectives

• To eliminate traditional impressional methods.

• To design, with aid of the computer, the future restoration is accordance with the preparation, the function and natural anatomy.

• To produce the restoration chairside.

• To machine the restoration by rotating device,sono or electro-erosion,laser etc..

• To improve restoration qualities-mechanical resistance,marginal fit,surface qualities and esthetics.

Advantages

• Negligible porosity in CADCAM core ceramics.

• Freedom from making impression.• Need for only single appointment.• Good patient acceptance.

• Need for costly equipments.• Lack of computer controlled processing

support for occlusal adjustment.• Technique sensitive.

Types of CADCAM

• Direct : Fully integrated CADCAM devices for chairside restorative approach.

• CADCAM stations are located at the dental office.

• Indirect method: It consists of several modules with at least distinctive CAD&CAM stations.

• The impression(optical) is taken in the dental office where the CAD operation is carried out.Data are transmitted to central CAM station for restoration manufacturing.

• Optical impression is taken in the dental office, collected information is then transmitted to a central station where CAD&CAM modules operate.

• Because of overall dimension and cost of the CADCAM machines, they are usually not located in a dental office,but more likely in a different treatment places converge.

• eg:Duret system• procera[Nobel biocare]• cicero system[elephant industries]• president DCS system[DCS dental].

DIRECT CADCAM System

• CEREC system has been marketed for several years with the improved CEREC2 introduced in mid-1990’s and upgraded to CEREC3 in 2000.

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

MATERIALS USED

• Vita Mark II [Vident]:contains sanidine[KALSi3O8] as a major crystalline phase with a glassy matrix.

• Dicor MGC:is a mica based machinable glass ceramic that contain 70 vol% of crystalline phase.

• The unique “HOUSE OF CARDS”microstructure found in Dicor MGC is due to interlocking of the small platelet shaped mica crystals with an average size of 1-2 microns.

• It leads to multiple crack deflection and ensures a greater strength than leucite containing ceramics.

• ProCad[ivoclar]: is a leucite containing ceramic.

• Vita Inceram Blocks [Vita Zahnfabrik]:• SPINEL blanks: Spinel are used for to

obtain an esthetically appealing, translucent ceramic structures.

• ALUMINA blanks:this has the advantage of the synthetic corundum that is prepared from bauxite in electric melting furnance.

• ZIRCONIA blanks: this combines the fracture toughness of the metastable tetragonal zirconium oxide referred to an ceramic steel.

LIMITATION IN CEREC

• The cerec system was acceptable with regard to the longetivity of adhesively bonded restoration , but the amount of manual correction to make material fit was too high.

• Poor marginal fit of restoration.

• Diamond disc was only tool for cutting.Hence it was important to incorporate an additional diamond cutting instrument.

• Lack of sophistication in machining of occlusal surface.

• Dentist’s required intensive training for CAD.So it was important to achieve easy and user friendly software for CAD.

CEREC 2:Improvisations in cerec 2

• Improvisations were made in CEREC2 such as

• 1.CAD module was implemented with a second form milling tool(a cylindrical,diamond bur) which provides six milling axes instead of three.

• 2.It has enchanced control software.

• 3.New camera provides more data with greater accuracy with a resolution from 25-50 microns.

• 4.It is capable of processing much more complicated restoration form & roughly developing occlusal surface.

• 5.Marginal adaptation of CEREC2 is improved.

CEREC3

• Software still easy & user friendly which uses window as operating systems.

• Precise restoration.• External & internal measuring.• Rapid production.• Imaging unit & milling unit can be linked

via various means.• Supported with online helps & design.

Advantages

• Time saving-one or two appointments required.• Time taken for making optical impression is 5 sec.• Wear hardness similar to enamel.• Less fracture due to the usage of single

homogenous block with negligible porosity.• Excellent polish & improved esthetics.• Good occlusal morphology.• Good patient acceptance.

INDIRECT CADCAM

• Eg: Cerec scan,cerec inlab,procera system.• CEREC SCAN:• Inclusive of both scaning &

milling device with laptop imaging device.• •

• CEREC INLAB:• Consists of a compact milling

unit with a in built scanner.It produces more precision restoration.Software runs as WINDOW 98.

• Procerra system:• Introduced by Dr.Matts

Anderson from Nobel Biocare.• Involves an industrial

CAD/CAM process.

Materials used

• Involves(densely sintered high purity inmdustrial aluminum oxide) core combined with a (low fusing veneering porcelain) fabricated by the pressed powder technique.

Technique Specification

• Computer aided designed copings of 0.2mm thickness is made from dense sintered industrial aluminium oxide with is translucent & tooth colored.

• Final morphology constructed with aluminium ceramic with matched thermal expansion.

Advantages

• Good clinical perfomance. • Good marginal adaptation.• Metal free & precision fit.• Reduced opposing wear.• Natural translucency & biocompactibility.• Enhanced esthetic & strength

Indication

• All single crown anterior & posterior for modified implant copings for direct cementation.

• Where minimum crown thickness only possible & light transmission through to the gingiva for good esthetics is critical.

• In situation where good moisture control is difficult & adhesive luting technique is contraindicated.

Copy milling

• A process of machining a structure using a device that traces the surface of a master metal, ceramic or polymer pattern & 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.

• Eg:Celay

CELAY Systems(Mikrona technologies)

• Developed by Dr.Stefan I.Eidenbenz at the university of Zurich in 1994.

• It is a precision copy milling machine that uses similar types of ceramic materials,but is not computer driven.

Technique Specification

• Based on a mechanical device that is used to trace the surface of a prefabricated pattern of the designed restoration made from a blue resin based composite which is produced either directly on die made from impression.

• Replica is mounted on one side of celay system(scanning side)and a ceramic block is mounted on the milling side.

• Uses sequential milling procedure proceeding from course to fine milling bur.

• Restoration are milled in 15-20min with internal & occlusal surfaces fully formed.

Materials Used

• Vitablocks similar to CEREC vitablocks.• Inceram alumina blocks are used to fabricate

single and multiple unit.• Inceram cores for production of all ceramic

crowns & bridges.• Inceram porous alumina is milled with the celay

system & subsequently infused with glass before application of the overlying porcelain

ADVANTAGES

• Marginal accuracy seem to be good, a little better than the cerec system.

• Good patient acceptance.• Less adjustment work.

HOT PRESSED, INJECTION MOULDED CERAMIC

• They are supplied as ingots.• These products are melted at high

temperature and injected into a moulded using lost wax process.

• They can be made into full contours or used as a substrate for conventional feldspathic porcelain buildup or layering technique.

• Example:• IPS Empress I,II [Ivoclar vivadent[• OPC• Alceram[ cerestore, innotek dental

corporation].

IPS EMPRESS

• Leucite reinforced glass ceramic material [40%-50%]

• Leucite crystals increase the strength and fracture resistance of the feldspathic glass matrix.

COMPOSITION• SiO3-59%-63%• K2O-10%-14%• Al2O3-17%-21%• CeO3-0.1%• Na3O-3.5%-6.5%• BaO-0-1.5%• B2O3-0.1%• CaO-0.5%-2.8%• TiO3-0.05%• PIGMENT-0.5-1%

TECHNIQUE

• Restoration is first waxed up and invested using the lost wax process.

• Ingots are softened before being pressed into a mould under pressure of 0.4MPa at 1150 C.

• Pressure maintained for 20 min during which time the tetragonal leucite crystals are dispersed throughout the restoration, giving a 40% concentration by volume.

Advantages

• Lack of metal or opaque ceramic core• Moderate flexural strength [similar to that

of Optec HSP]• Excellent fit and esthetics.• Increased durability and wear

compactibility• High transluency and natural esthetics.

Disadvantages

• Potential for fracture in posterior region.• Need for special laboratory equipment.

PROPERTIES

• Bending \fatigue strength:200MPa.• Marginal gap width:50 microns.• Flexural strength:220MPa.• Marginal integrity:<50 microns.

INDICATION

• Inlays\onlays• Veneers.• Full coverage crowns.

IPS EMPRESS 2

• Principle:• increasing the strength of the

material without compromising its transluency.

• High strength of IPS Empress2 replaces older IPS Empress.

MATERIAL

• Schwieger et al developed a highly crystalline [>60%] microstructure of densely arranged lithium disilicate crystals of size 0.5-5 microns were uniformly bonded in a glassy matrix.

• It is composed of homogenously shaped elongated lithium disilicate crystals arranged in a interlocking structure.

• This hinders crack propogation to elevate fracture toughness and flexural strength.

• In addition to lithium disilicate ,lithium ortho phosphate occurs as a secondary crystal phase measuring 0.1-0.3 microns which are comparatively small.

COMPOSITION

• SiO3-57-80%• Al2O3-0-5%• La2O3-0.1-6%• MgO-0-5%• ZnO-0-8%• K2O –0-13%• Li2O3-11-19%• P2O3-0-11%• Pigment-0-8%m

Layering ceramic

• Sintered glass ceramics.• Supplied in powder form-

dentin ,incisal,transparent.• Their crystalline phase consist of

fluoroapatite.

COMPOSITION

• SiO3 -45-70%• Al2O3 -5-22%• P2O3 -0.5-6.5%• K2O -3-9%• Na2O -4-13%• CaO -0-11%• F -0.1-2.5%• PIGMENT-0.3%

Indication

• Anterior and posterior crowns and bridges.

ALCERAM• MATERIAL:• Aluminium oxide and magnesium oxide- react

to form magnesium aluminate spinel (MgAl2O4).• Magnesium aluminate spinel occupies a greater volume

than the combination of magnesium oxide and aluminium oxide, the resultant volume increase compensate for the firing shrinkage (starling et al).

• Non shrink ceramics.

COMPOSITION

• Al2O3 -43.29%• Al2O3 -17.32%• BaO-SiO2-Al2O3 GLASS FRIT -12.99%• (58%BaO,42%SiO2,5%Al2O3) • MgO -8.66%• Edger plastic kaolin -3.90%• Calcium stearate -0.86%• Accrawax -0.86%• Silicone resin -12.12%

• Calcium stearate and accrawax- binder and lubricant.

• Barium glass frit and silicon resin –forms glass phase.

• On temperature over 1300 C the magnesium and some alumina combine to form spinel.

• Crystal content of ceramic-70%-95% by body wt.

• Cerestore coping is placed on the master die and a suitable aluminous veneer porcelain is used to complete the crown

PROPERTIES

• Density-2.80g\cc• Flexural strength-125MPa• Compressive strength-450MPa• Low coefficiet of thermal expansion-

below8*10-6 C.

Thank you

For more details please visit www.indiandentalacademy.com

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