RECENT ADVANCES IN DENTAL CERAMICS

CONTENTSIntroductionHistory Glass infiltrated aluminaInceramsProcera all ceramPressable ceramicsMachinable ceramicsCAD CAM

INTRODUCTIONThough conventional ceramics provide esthetically pleasing retorations they have many drawbacks which limit their use.With more and more studies coming in the field of ceramics and with the advent of digital technology newer and better products are flooding the market these days.The chinese clay of olden days have become the unavoidable product in esthetic dentistry...

* reinforced ceramic core systems metal-ceramicsresin-bonded ceramics

HISTORYSince the stone age ceramics have been important for humans.

1789-de_chemant & Duchateau.1822-baking process.1825-commercial production by Stockton.1903-Dr.Charles Land-first ceramic crown1962-Patents by weinstien and wenstein.1965-Mclean & Hughes

CLASSIFICATIONUSECOMPOSITIONPROCESSING METHODFIRING TEMP.MICRO STRUCTURETRANSLUCENCYABRASIVENESSOPAQUETRANSLUCENTTRANSPARENTGLASS

CRYTALLINE

CRYSTAL -GLASSLOW FUSING

MEDIUM

HIGH FUSING

SINTERING

PARTIAL SINT

GLASS INFIL.

CAD-CAM

COPY MILLINGPURE ALUMINA

P.ZIRCONIA

P.SILICA GLASS

LEUCITE.G.CER

LITHIA BASED

ANT.POST.CROWNSVENEERSP&C

WHY DO WE NEED ADVANCED PRODUCTS ???

One of the most serious drawbacks with the early dental porcelains were their lack of strength and toughness, which seriously limited their use. In order to overcome these problems, there are two possible solution. One solution is to provide the dental porcelain with support from a stronger substructure. The other option is to produce ceramics, which are stronger and tougher.

Metal free ceramic systemsAll ceramic systems can provide better esthetics.Wide range of tranlucency opacities are availableSoft tissue healthNo over contouring

Glass infiltrated aluminaIn-ceram aluminaSupplied as one of the three core ceramics.1)in-ceram spinell2)in-ceram alumina3)in-ceram zirconia

In - ceramA slurry of material is slip cast on porous refractory die and heated in a furnace to produce a partially sineterd coping.This coping is infiltrated with glass at temp1100*c -4hrs

In-ceram aluminaIndication-anterior and posterior crowns and anterior 3-unit FPDs.Flexuarl strength-500mPaThe final ICA core consists of 70wt% alumina and 30wt%sodiumlnathanum glass.

Advantages Moderately high flexural strength and fracture resistance.A metal free structureAn ability to be used succesfully with conventional luting cements

Drawbacks Marginal seal is not as good as procera-all ceram or IPS Empress.High degree of opacityInability to be etchedTechnique sensitive

In ceram spinnelIndications-anterior single unit creowna,inlays,onlays & veneers.It is the most translucent among the three .It was introduced as an aletrnative to ICA

Improved translucency.....better esthetics.

single anteriorsanterior bridgessingle posteriorsposterior bridges InlaysonlaysveneersIn-Ceram SpinellXXXXIn-Ceram AluminaXXX In-Ceram ZirconiaXX

In ceram zirconiaIndication-posterior crownsNot recommended in anteriors due to the high degree of opacityBut has good modulous of elasticity and fracture toghness.Though it has better strength its use is limited to posteriors due to its greater opacity.

Castable and machinable ceramicsWhen used in posteriors ceramic crowns are succeptible to fracture.Critical flaw...??

First commercially available castable ceramic-dicor,developed by corning glass works.Dicor is a castable glass.Indicated for onlays,facial veneers,full crown restorations.technique......ceramming

Procera all ceram Composed of densely sintered high purity Aluminium oxide core+all ceram veneering porcelain.Contains 99% alumina.It is one of the hardest among the ceramics.

Indications-anterior & posterior crowns,veneers,onlays...Procera scanner is used.It is developed through CAD-CAM processing.

CAD-CAM ceramicsComputer aided designing and computer aided milling.The internal surface of inlays or crowns is ground with diamond discs according to the scanned image of the praparation

ADVANTAGESNo wear of the opposing toothStrengthFracture resistanceLow translucensy

Lava zirconiaThey are zirconia based products.First the milled prosthesis is removed from the milling unit.The zirconia frame work is placed in the cercon furnace and fire at 1350*C for 6 hours.

The purest tetragonal zirconia has got the greatest fracture toughness and flexural strength.Contra indicated in patients with bruxism.Only minimal occlusal reduction of 2mm needed.

Finesse all ceramicIt is a new product patended to dentsply.Indications-crowns anterior&posterior Veneers Inlays onlays

Finesse All-Ceramic achieve an ideal bond without the need to create a wash layerThus saving time and enhancing the strength of the restoration.It is a leucite reinforced ceramic glass material.Flexural strength- 125mPa

"Pressing" - lost wax injection moldingAt 930C, for 20 minInherently fluorescent Ideal transparency range from (clear) to (opaceous)

PRESSABLE CERAMICSIntroduces by MAC CULLOCH IN 1968Here,the glass is formed into the devised shape.Then it is subjected to partial devitrification.a presssure moulding technique is followed.

IPS empress-is a glass ceramic avialable as ingots,Which can be heated and pressed until the ingots flows into a mold.It contains higher concentration of leucite crystals that increase the resistance to crack propagation.It can be tained ,glazed or built up by layering technique.

No metal componentTranslucent ceramic coreModerately high flexural strengthExcellent fitExcellent estheticsADVANTAGES

Disadvantages Potential to fracture(in posterior)Requires a resin cement to micromechanically bond to the tooth structure.

Y - TZP...??

Yttrium tetragonal zirconia polycrystalOne the latest advacements in the field of all ceramic restorations.Phase transformation from monoclonal to tetragonal on firing.Adding zerconia stablizes the core during this phase transformation.

Also the presence of water causes crack propagation and stress corrosion reactions.But Y-TZP substructures are independent of this phenomena.In vitro studies show a flexural strength of 900-1200mPa.

Hydroxy apatite based ceramicsCera pearl,developed by Kyocera co. in CA.Here the main ceystalline phase is oxy apatite which can be tranformed to hydroxy apatite on hydration.Commonly used in implants...for better flexural strength and bonding.

Shade Dimensions of colorMetamerism & FlouresenceHue

Chroma

Value

Conclusion Advances in the field of ceramics gives hand full of newer products for the dentist.Which will surely enhance the esthetic and strength characters.A carefull selection of these products are essential for successful outcome.

Bibliography Text book of dental materials-Anusavice.Dental technitian news letter-2009 marchText book of ceramics fabrication-Naylor.Recent advances in ceramics-Dr.Jennifer,ohio,USA

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