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ALLOYS USED IN METALALLOYS USED IN METAL
CERAMICSCERAMICS
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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ContentsContents
 Basic Materials used in dentistryBasic Materials used in dentistry
 Metals and their propertiesMetals ...
Basic Materials used in DentistryBasic Materials used in Dentistry
 ClassificationClassification
CERAMICS
METALS
POLYMER
...
MetalsMetals
 A crystalline material that consists ofA crystalline material that consists of
positively charged ions in a...
AlloysAlloys
 A material that exhibits metallic propertiesA material that exhibits metallic properties
and is composed of...
Inter metallic CompoundsInter metallic Compounds
 A chemical compound whose componentsA chemical compound whose component...
PolymersPolymers
 A material that is made up of repeatingA material that is made up of repeating
units, orunits, or mers....
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MetalsMetals
 A crystalline material that consists of positivelyA crystalline material that consists of positively
charge...
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Characteristic Properties Of MetalsCharacteristic Properties Of Metals
 Metals are usuallyMetals are usually
 HardHard
...
OccurrenceOccurrence
 Metals occur either on pure elements or inMetals occur either on pure elements or in
compounds with...
Classification Of MetalsClassification Of Metals
 Pure Metal or Mixture of Metals – AlloysPure Metal or Mixture of Metals...
Noble MetalNoble Metal
 Noble Metal is one whose compounds areNoble Metal is one whose compounds are
decomposable by heat...
Base MetalsBase Metals
 Base metal is one whose compounds withBase metal is one whose compounds with
oxygen are not decom...
Cast MetalCast Metal
Cast metal is any metal that is melted andCast metal is any metal that is melted and
poured into a mo...
Wrought MetalWrought Metal
Wrought metal is a cast metal, which has beenWrought metal is a cast metal, which has been
work...
Another Classification Of MetalsAnother Classification Of Metals
 Light Metal – e.g., Al.Light Metal – e.g., Al.
 Heavy ...
Microscopic Structure Of MetalsMicroscopic Structure Of Metals
 Most metals have crystalline structure in solidMost metal...
Metallic BondMetallic Bond
 Primary BondsPrimary Bonds
1.1. Ionic BondsIonic Bonds
2.2. Covalent BondsCovalent Bonds
3.3....
Fabrication (Shaping) Methods OfFabrication (Shaping) Methods Of
MetalsMetals
 Casting – is the best and popular method.C...
Fabrication (Shaping) Methods OfFabrication (Shaping) Methods Of
Metals (Contd.)Metals (Contd.)
 Extrusion - The process ...
Solidification Of Pure MetalSolidification Of Pure Metal
 Pure metal has a melting point-known as FusionPure metal has a ...
Solidification Of Pure Metal (Contd.)Solidification Of Pure Metal (Contd.)
 MechanismMechanism
When the solid metal chang...
Mechanism of CrystallizationMechanism of Crystallization
 A pure metal may crystallize in a tree-branchA pure metal may c...
Mechanism of CrystallizationMechanism of Crystallization
(contd.)(contd.)
 A pure metal crystallizes from nuclei in a pat...
Mechanism of CrystallizationMechanism of Crystallization
(contd.)(contd.)
 Most noble metal casting alloys solidify with ...
Mechanism of CrystallizationMechanism of Crystallization
(contd.)(contd.)
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Importance of grain boundaryImportance of grain boundary
 During permanent deformation of ductile dentalDuring permanent ...
Control Of Grain SizeControl Of Grain Size
 More nuclei in a given area results in smallerMore nuclei in a given area res...
Importance of grain sizeImportance of grain size
 For noble metal casting alloys the yield strengthFor noble metal castin...
Crystal Space LatticeCrystal Space Lattice
 The formed crystals in a metal are arranged in aThe formed crystals in a meta...
Crystal Space LatticeCrystal Space Lattice
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Lattice Imperfections Or DefectsLattice Imperfections Or Defects
 During crystal growth they do not meet inDuring crystal...
Edge Dislocation Slip PlaneEdge Dislocation Slip Plane
 The line defects in a lattice can be made to slipThe line defects...
Edge Dislocation Slip PlaneEdge Dislocation Slip Plane
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Edge Dislocation Slip PlaneEdge Dislocation Slip Plane
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Edge Dislocation and Slip PlaneEdge Dislocation and Slip Plane
(Contd.)(Contd.)
 The strength and ductility of the metal ...
Edge Dislocation and Slip PlaneEdge Dislocation and Slip Plane
(Contd.)(Contd.)
 If this is done at room temperature with...
Cooling Pattern of Liquid MetalCooling Pattern of Liquid Metal
During SolidificationDuring Solidification
 Liquidus tempe...
Cooling Pattern of Liquid MetalCooling Pattern of Liquid Metal
During SolidificationDuring Solidification
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Working On MetalsWorking On Metals
 Deformation of Metal – Cold WorkDeformation of Metal – Cold Work
–– Hot WorkHot Work
...
Working On Metals (Contd.)Working On Metals (Contd.)
 Cold Work – when a metal is worked uponCold Work – when a metal is ...
Working On Metals (Contd.)Working On Metals (Contd.)
 Cold working results inCold working results in
• Increased surface ...
Working On Metals (Contd.)Working On Metals (Contd.)
 Annealing – heat treatment of metal or glass toAnnealing – heat tre...
RecoveryRecovery
 During recovery, cold work properties begin toDuring recovery, cold work properties begin to
disappear....
RecrystallizationRecrystallization
 The temperature at which the Old grainsThe temperature at which the Old grains
disapp...
Grain GrowthGrain Growth
 Grain growth stops when a coarse grainGrain growth stops when a coarse grain
structure is reach...
AnnealingAnnealing
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Fracture Of MetalFracture Of Metal
 If cold work is continued then the metalIf cold work is continued then the metal
even...
ALLOYSALLOYS
 Combination of two or more metals which areCombination of two or more metals which are
generally mutually s...
Methods of AlloyingMethods of Alloying
 By melting together the base metal (main) andBy melting together the base metal (...
Objectives of AlloyingObjectives of Alloying
1.1. To increase hardness and strength.To increase hardness and strength.
2.2...
Objectives of Alloying (Contd.)Objectives of Alloying (Contd.)
5.5. To make casting or working on the metal easy.To make c...
Types of AlloysTypes of Alloys
 Ferrous alloys - in which iron is the base metalFerrous alloys - in which iron is the bas...
Types of Alloys (Contd.)Types of Alloys (Contd.)
 Die-casting alloys-zinc containing aluminum andDie-casting alloys-zinc ...
Classification Of AlloysClassification Of Alloys
 On the basis of number of metalsOn the basis of number of metals presen...
Classification Of Alloys (Contd.)Classification Of Alloys (Contd.)
 On the basis of miscibility (solubility) of atomsOn t...
Solid SolutionSolid Solution
 Complete solubility.Complete solubility.
 These are the alloys in which the ingredient met...
Solid SolutionSolid Solution
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Solid Solution (Contd.)Solid Solution (Contd.)
 Some examples of Solid solutions are,Some examples of Solid solutions are...
Solid Solution (Contd.)Solid Solution (Contd.)
 The solid-solution alloys may be;The solid-solution alloys may be;
1.1. S...
Solid Solution (Contd.)Solid Solution (Contd.)
a.a. ORDERED ARRANGEMENTORDERED ARRANGEMENT
 This produces an ordered spac...
Solid Solution (Contd.)Solid Solution (Contd.)
 DISORDERED ARRANGEMENTDISORDERED ARRANGEMENT
This produces disordered spa...
DISORDERED ARRANGEMENTDISORDERED ARRANGEMENT
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Solid Solution (Contd.)Solid Solution (Contd.)
 INTERSTITIAL SOLID SOLUTION ALLOYINTERSTITIAL SOLID SOLUTION ALLOY
The a...
Conditions Favoring Solid-SolubilityConditions Favoring Solid-Solubility
 Atom size - if the atom sizes of the mixing met...
Properties Of Solid-solution Type OfProperties Of Solid-solution Type Of
AlloysAlloys
 Strong and hard.Strong and hard.
...
Eutectic AlloysEutectic Alloys
 Complete in-solubility in solid state.Complete in-solubility in solid state.
 The ingred...
Eutectic AlloysEutectic Alloys
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Eutectic Alloys (Contd.)Eutectic Alloys (Contd.)
 In this type of alloy, there is one particularIn this type of alloy, th...
Eutectic Alloys (Contd.)Eutectic Alloys (Contd.)
 These alloys are called eutectic because theThese alloys are called eut...
Eutectic Alloys (Contd.)Eutectic Alloys (Contd.)
 Properties – BrittleProperties – Brittle
Less strongLess strong
Less re...
Inter metallic CompoundsInter metallic Compounds
 Inter metallic compounds are those when theInter metallic compounds are...
Inter metallic Compounds (Contd.)Inter metallic Compounds (Contd.)
 Very hard and brittle.Very hard and brittle.
 Proper...
Peritectic AlloysPeritectic Alloys
 E.g. Platinum-Silver in casting alloyE.g. Platinum-Silver in casting alloy
 Limited ...
Heat TreatmentHeat Treatment
 Heat treatment (not melting) of metals in theHeat treatment (not melting) of metals in the
...
Heat Treatment (Contd.)Heat Treatment (Contd.)
 Important criteria in this process are:Important criteria in this process...
Purpose of Heat TreatmentPurpose of Heat Treatment
 Shaping and working on the appliance in theShaping and working on the...
Clinical significance of heatClinical significance of heat
treatmenttreatment
 Type I and II gold alloys usually do not h...
Types of Heat TreatmentTypes of Heat Treatment
 Softening Heat treatmentSoftening Heat treatment
 Hardening Heat treatme...
Softening heat treatment
 Also known as ANNEALING. This is done forAlso known as ANNEALING. This is done for
structures w...
Softening heat treatment(Contd.)
 Result of this is reduction in strength, hardnessResult of this is reduction in strengt...
Hardening heat treatment
 This is done for cast removable partialThis is done for cast removable partial
dentures, saddle...
Hardening heat treatment(Contd.)
 The result of this is increase in strength,The result of this is increase in strength,
...
Solution Heat Treatment Or
Solution-Hardening
 When the alloy is heat soaked, any precipitationsWhen the alloy is heat so...
Age Hardening
 After solution heat treatment, the alloy is onceAfter solution heat treatment, the alloy is once
again hea...
Clinical significance of heatClinical significance of heat
treatments in metal ceramic alloystreatments in metal ceramic a...
Clinical significance of heatClinical significance of heat
treatments in metal ceramic alloystreatments in metal ceramic a...
Different Metals Used In DentistryDifferent Metals Used In Dentistry
Gold (Au)Gold (Au)
 noble metalnoble metal
 provide...
PalladiumPalladium
 Palladium, a member of the platinum group, is a noblePalladium, a member of the platinum group, is a ...
PlatinumPlatinum
 Platinum is a member of the platinum groupPlatinum is a member of the platinum group
and is a noble met...
IridiumIridium
 Iridium is a member of the platinum groupIridium is a member of the platinum group
and is a noble metal.a...
Ruthenium (Ru)Ruthenium (Ru)
 Ruthenium is a member of the palladiumRuthenium is a member of the palladium
group and is a...
SilverSilver
 Although silver is a precious element, it is notAlthough silver is a precious element, it is not
universall...
Silver (Contd)Silver (Contd)

Silver possesses a high affinity for oxygenSilver possesses a high affinity for oxygen
abso...
AluminiumAluminium
 Aluminum is added to lower the melting range ofAluminum is added to lower the melting range of
nickel...
BerylliumBeryllium
 Like aluminum, beryllium lowers the meltingLike aluminum, beryllium lowers the melting
range of nicke...
BoronBoron
 Boron is a deoxidizer.Boron is a deoxidizer.
 For nickel-based alloys, it is a hardening agent andFor nickel...
Chromium (Cr)Chromium (Cr)
 Chromium is a solid solution hardeningChromium is a solid solution hardening
agent that contr...
CobaltCobalt (Co)(Co)
 Cobalt is an alternative to the nickel-basedCobalt is an alternative to the nickel-based
alloys, b...
Copper (Cu)Copper (Cu)
 Copper serves as a hardening and strengtheningCopper serves as a hardening and strengthening
agen...
GalliumGallium (Ga)(Ga)
 Gallium is added to silver-free porcelainGallium is added to silver-free porcelain
alloys to com...
IndiumIndium
 Serves many functions in gold-based metalServes many functions in gold-based metal
ceramic alloys.ceramic a...
Iron (Fe)Iron (Fe)
 Iron is added to some gold-based porcelainIron is added to some gold-based porcelain
systems for hard...
Manganese (Mn)Manganese (Mn)
 Manganese is an oxide scavenger and aManganese is an oxide scavenger and a
hardening agent ...
Molybdenum (Mo)Molybdenum (Mo)
 Molybdenum improves corrosion resistance,Molybdenum improves corrosion resistance,
influe...
Nickel (Ni)Nickel (Ni)
 Nickel has been selected as a base for porcelainNickel has been selected as a base for porcelain
...
Tin (Sn)Tin (Sn)
 Tin is a hardening agent that acts to lowerTin is a hardening agent that acts to lower
the melting rang...
Titanium (Ti)Titanium (Ti)
 Like aluminum and beryllium, titanium isLike aluminum and beryllium, titanium is
added to low...
Zinc (Zn)Zinc (Zn)
 Zinc helps lower the melting range of anZinc helps lower the melting range of an
alloy and acts as a ...
Need For Dental casting alloysNeed For Dental casting alloys
 The Major factors areThe Major factors are
 Economy – To p...
Historical Perspective On DentalHistorical Perspective On Dental
Casting AlloysCasting Alloys
 The history of dental cast...
Historical Perspective On DentalHistorical Perspective On Dental
Casting Alloys (contd)Casting Alloys (contd)
 Taggarts p...
Historical Perspective On DentalHistorical Perspective On Dental
Casting Alloys (contd)Casting Alloys (contd)
 Because pu...
Historical Perspective On DentalHistorical Perspective On Dental
Casting Alloys (contd)Casting Alloys (contd)
 At that ti...
Historical Perspective On DentalHistorical Perspective On Dental
Casting Alloys (contd)Casting Alloys (contd)
 The base m...
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Desirable Properties Of CastingDesirable Properties Of Casting
Alloys: The metals must exhibitAlloys: The metals must exhi...
Desirable Properties Of CastingDesirable Properties Of Casting
Alloys: The metals must exhibitAlloys: The metals must exhi...
Alloys type by function - 1932Alloys type by function - 1932
Type I gold alloysType I gold alloys Soft (VHN 50 TO 90)Soft ...
Alloy type by functionAlloy type by function
 Type I ;- small inlays easily burnished andType I ;- small inlays easily bu...
Classification Of Alloys By ADA 1984Classification Of Alloys By ADA 1984
Alloy TypeAlloy Type Total Noble contentTotal Nob...
Alloy classification based on color orAlloy classification based on color or
compositioncomposition
According to their col...
Alloy classification based on color orAlloy classification based on color or
composition (Cond..)composition (Cond..)
 Lo...
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Metal Ceramic RestorationMetal Ceramic Restoration
 By Definition – Partial crown, full crown orBy Definition – Partial c...
History of metal ceramic alloysHistory of metal ceramic alloys
 1789 - The first porcelain tooth material was1789 - The f...
History of metal ceramic alloysHistory of metal ceramic alloys
 1808- Fonzi, an Italian dentist, invented a "terrometalli...
History of metal ceramic alloysHistory of metal ceramic alloys
 1903 - Dr. Charles Land introduced one of the1903 - Dr. C...
History of metal ceramic alloysHistory of metal ceramic alloys
 1962 - Weinstein et al , responsible for the patents of19...
Requirements for metal ceramicRequirements for metal ceramic
alloysalloys
 The chief objection for the use of dental porc...
Metal – ceramic bondingMetal – ceramic bonding
 Factors controlling metal ceramic adhesionFactors controlling metal ceram...
Chemical bondingChemical bonding
 The original metal ceramic alloy containing 88%The original metal ceramic alloy contain...
Chemical bondingChemical bonding
 The addition of 1% base metals to goldThe addition of 1% base metals to gold
palladium ...
Mechanical interlockingMechanical interlocking
 Roughness or generally the topography ofRoughness or generally the topogr...
Mechanical interlockingMechanical interlocking
 Roughness can reduce adhesion if ceramicRoughness can reduce adhesion if ...
Thermal compatibilityThermal compatibility
 Refers to the ability of a metal and its veneeringRefers to the ability of a ...
Thermal compatibilityThermal compatibility
 If the porcelain has much larger coefficientIf the porcelain has much larger ...
Thermal compatibilityThermal compatibility
 Porcelains have coefficient of thermal expansionPorcelains have coefficient o...
Sag resistanceSag resistance
 Coefficient of thermal expansion tends toCoefficient of thermal expansion tends to
have a r...
Selection of Metal Ceramic AlloysSelection of Metal Ceramic Alloys
Physical properties includes..Physical properties inclu...
ColorColor
 The most important obvious property of anThe most important obvious property of an
alloy – Coloralloy – Color...
Noble Metal ContentNoble Metal Content
Indirectly denotes…..Indirectly denotes…..
 Corrosion resistance of the alloysCorr...
HardnessHardness
 Definition - Resistance of material to plasticDefinition - Resistance of material to plastic
deformatio...
Yield StrengthYield Strength
 The stress at which a test specimen exhibitsThe stress at which a test specimen exhibits
a ...
ElongationElongation
 Maximum amount of plastic strain a tensileMaximum amount of plastic strain a tensile
test specimen ...
Fusion TemperatureFusion Temperature
 Temperature at which the metal solidifiesTemperature at which the metal solidifies
...
Chemical PropertiesChemical Properties
 Tarnish and corrosion resistanceTarnish and corrosion resistance
 Tarnish is a t...
Corrosion resistanceCorrosion resistance
 Corrosion is the physical dissolution of a materialCorrosion is the physical di...
Lab workability and Casting AccuracyLab workability and Casting Accuracy
 To provide clinically acceptable castings byTo ...
Bio CompatibilityBio Compatibility
Base metal alloys – Nickel (Ni) and Beryllium (Be)Base metal alloys – Nickel (Ni) and B...
CompositionComposition
 Key factor since components of alloyKey factor since components of alloy
influences color of porc...
Economic considerationsEconomic considerations
 Cost of metals is major concern for the useCost of metals is major concer...
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High Gold AlloysHigh Gold Alloys
 PFM introduced to dental profession withPFM introduced to dental profession with
introd...
High gold alloysHigh gold alloys
 Gold content varies from 78% -87% by weight and nobleGold content varies from 78% -87% ...
Gold,Platinum,Palladium AlloysGold,Platinum,Palladium Alloys
 Composition ;-Composition ;-
 Gold: 75%-88%Gold: 75%-88%
...
Gold,Platinum,PalladiumGold,Platinum,Palladium
Alloys(Contd)Alloys(Contd)
AdvantagesAdvantages
 Excellent castabilityExce...
Gold,Platinum,Palladium AlloysGold,Platinum,Palladium Alloys
(Contd)(Contd)
 Disadvantages;-Disadvantages;-
 High costHi...
Gold Palladium Silver AlloysGold Palladium Silver Alloys
Introduced in 1970 as will ceram wIntroduced in 1970 as will cera...
Gold Palladium Silver AlloysGold Palladium Silver Alloys
(Contd..)(Contd..)
AdvantagesAdvantages
 Less expensive than Au-...
Gold Palladium Silver AlloysGold Palladium Silver Alloys
(Contd..)(Contd..)
DisadvantagesDisadvantages
 High silver conte...
Gold-Palladium-Silver (low silverGold-Palladium-Silver (low silver
group)group)
CompositionComposition
 Gold – 52% - 77%G...
Gold-Palladium-Silver (low silverGold-Palladium-Silver (low silver
group)group)
 AdvantagesAdvantages
 Less expensive th...
Gold-Palladium-Silver (low silverGold-Palladium-Silver (low silver
group)group)
 DisadvantagesDisadvantages
 High costHi...
Gold-Palladium alloysGold-Palladium alloys
CompositionComposition
 Gold – 44% -55%Gold – 44% -55%
 Palladium – 35% - 45%...
Gold-Palladium alloysGold-Palladium alloys
AdvantagesAdvantages
 Excellent castabilityExcellent castability
 Good bond s...
Gold-Palladium alloysGold-Palladium alloys
DisadvantagesDisadvantages
 High costHigh cost
 Not thermally compatible with...
Palladium-Silver alloysPalladium-Silver alloys
CompositionComposition
 Palladium – 55% - 60%Palladium – 55% - 60%
 Silve...
Palladium-Silver alloys (contd)Palladium-Silver alloys (contd)
AdvantagesAdvantages
 Good castability (whenGood castabili...
Palladium-Silver alloys (contd)Palladium-Silver alloys (contd)
DisadvantagesDisadvantages
 High coefficient of thermalHig...
Palladium-cobalt alloysPalladium-cobalt alloys
CompositionComposition
 Palladium: 78%-88%Palladium: 78%-88%
 Cobalt: 4%-...
Palladium-cobalt alloysPalladium-cobalt alloys
AdvantagesAdvantages
 Low costLow cost
 Reportedly good sag resistanceRep...
Palladium-cobalt alloysPalladium-cobalt alloys
DisadvantagesDisadvantages
 More compatible with higher expansionMore comp...
High Palladium-Silver-Gold alloysHigh Palladium-Silver-Gold alloys
CompositionComposition
 Palladium: 75%-86%Palladium: 7...
High Palladium-Silver-Gold alloysHigh Palladium-Silver-Gold alloys
 AdvantagesAdvantages
 Low costLow cost
 Low density...
High Palladium-Silver-Gold alloysHigh Palladium-Silver-Gold alloys
DisadvantagesDisadvantages
 A relatively new alloy gro...
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
Alloys used in metal ceramic/ cosmetic dentistry training
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Transcript of "Alloys used in metal ceramic/ cosmetic dentistry training"

  1. 1. ALLOYS USED IN METALALLOYS USED IN METAL CERAMICSCERAMICS INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. ContentsContents  Basic Materials used in dentistryBasic Materials used in dentistry  Metals and their propertiesMetals and their properties  Alloys and their propertiesAlloys and their properties  Metal ceramic alloysMetal ceramic alloys www.indiandentalacademy.com
  3. 3. Basic Materials used in DentistryBasic Materials used in Dentistry  ClassificationClassification CERAMICS METALS POLYMER INORGANIC SALT CRYSTALLINE CERAMICS GLASSES ALLOYS INTERMETTALIC COMPOUNDS RIGID POLYMERS WAXES ELASTOMERS www.indiandentalacademy.com
  4. 4. MetalsMetals  A crystalline material that consists ofA crystalline material that consists of positively charged ions in an ordered, closelypositively charged ions in an ordered, closely packed arrangement and bonded with apacked arrangement and bonded with a cloud of b-ee electrons. This type of bond,cloud of b-ee electrons. This type of bond, called acalled a metallic bond,metallic bond, is responsible foris responsible for many of the properties of metals-electricalmany of the properties of metals-electrical and ther­mal conductivity, metallic luster,and ther­mal conductivity, metallic luster, and (usually) high strengthand (usually) high strength www.indiandentalacademy.com
  5. 5. AlloysAlloys  A material that exhibits metallic propertiesA material that exhibits metallic properties and is composed of one or more elements-atand is composed of one or more elements-at least one of which is a metal. For example,least one of which is a metal. For example, steel is an alloy of iron and carbon, brass issteel is an alloy of iron and carbon, brass is an alloy of copper and zinc, and bronze is anan alloy of copper and zinc, and bronze is an alloy of copper and tin.alloy of copper and tin. www.indiandentalacademy.com
  6. 6. Inter metallic CompoundsInter metallic Compounds  A chemical compound whose componentsA chemical compound whose components are metals. The gamma phase of amalgam,are metals. The gamma phase of amalgam, Ag3Sn, is an example of an inter metallicAg3Sn, is an example of an inter metallic compound.compound. www.indiandentalacademy.com
  7. 7. PolymersPolymers  A material that is made up of repeatingA material that is made up of repeating units, orunits, or mers.mers. Most polymers are based on aMost polymers are based on a carbon (-C-C-C-C-) backbone in thecarbon (-C-C-C-C-) backbone in the polymer chain, al­though a silicone (-O-Si-polymer chain, al­though a silicone (-O-Si- O-Si-O-) backbone is im­portant in manyO-Si-O-) backbone is im­portant in many polymerspolymers www.indiandentalacademy.com
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  9. 9. MetalsMetals  A crystalline material that consists of positivelyA crystalline material that consists of positively charged ions in an ordered, closely packedcharged ions in an ordered, closely packed arrange­ment and bonded with a cloud of b-eearrange­ment and bonded with a cloud of b-ee electrons. This type of bond, called aelectrons. This type of bond, called a metallicmetallic bond,bond, is responsible for many of the properties ofis responsible for many of the properties of metals-electrical and ther­mal conductivity,metals-electrical and ther­mal conductivity, metallic luster, and (usually) high strengthmetallic luster, and (usually) high strength www.indiandentalacademy.com
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  11. 11. Characteristic Properties Of MetalsCharacteristic Properties Of Metals  Metals are usuallyMetals are usually  HardHard  LustrousLustrous  DenseDense  Good conductors of heat and electricityGood conductors of heat and electricity  OpaqueOpaque  Malleable and ductileMalleable and ductile  They give electro positive ions in solutionThey give electro positive ions in solution www.indiandentalacademy.com
  12. 12. OccurrenceOccurrence  Metals occur either on pure elements or inMetals occur either on pure elements or in compounds with other elements .compounds with other elements . Example; Gold(Au)Example; Gold(Au) Silver(Ag)Silver(Ag) Copper Obtained as CuCopper Obtained as Cu22S, CuSS, CuS Iron Obtained as FeIron Obtained as Fe22OO33 Pure Elements Compounds www.indiandentalacademy.com
  13. 13. Classification Of MetalsClassification Of Metals  Pure Metal or Mixture of Metals – AlloysPure Metal or Mixture of Metals – Alloys  Base Metal or Noble MetalBase Metal or Noble Metal  Cast metal or wrought metalCast metal or wrought metal www.indiandentalacademy.com
  14. 14. Noble MetalNoble Metal  Noble Metal is one whose compounds areNoble Metal is one whose compounds are decomposable by heat alone at a temperaturedecomposable by heat alone at a temperature not exceeding that of redness.not exceeding that of redness.  They are corrosion and oxidation resistantThey are corrosion and oxidation resistant because of inertness and chemical resistance.because of inertness and chemical resistance.  8 Noble metals used in dentistry are Au, Pt, Pd,8 Noble metals used in dentistry are Au, Pt, Pd, Ir, Os, Rh, Ru, Ag.Ir, Os, Rh, Ru, Ag. www.indiandentalacademy.com
  15. 15. Base MetalsBase Metals  Base metal is one whose compounds withBase metal is one whose compounds with oxygen are not decomposed by heat alone,oxygen are not decomposed by heat alone, retaining oxygen at high temperature.retaining oxygen at high temperature.  A metal, which is easily oxidized when heated inA metal, which is easily oxidized when heated in air, is a base metal.air, is a base metal.  Examples: Ni, Cr, Co, Fe, Al, Sn, Pb, etcExamples: Ni, Cr, Co, Fe, Al, Sn, Pb, etc www.indiandentalacademy.com
  16. 16. Cast MetalCast Metal Cast metal is any metal that is melted andCast metal is any metal that is melted and poured into a mould.poured into a mould. www.indiandentalacademy.com
  17. 17. Wrought MetalWrought Metal Wrought metal is a cast metal, which has beenWrought metal is a cast metal, which has been worked upon, in cold condition – i.e, withoutworked upon, in cold condition – i.e, without heating.heating. www.indiandentalacademy.com
  18. 18. Another Classification Of MetalsAnother Classification Of Metals  Light Metal – e.g., Al.Light Metal – e.g., Al.  Heavy Metal – e.g., Fe.Heavy Metal – e.g., Fe.  High Melting Metal – e.g., Co, Cr.High Melting Metal – e.g., Co, Cr.  Low Melting Metal – e.g., Sn.Low Melting Metal – e.g., Sn.  High Ductile and Malleable metal – e.g., Au.High Ductile and Malleable metal – e.g., Au. www.indiandentalacademy.com
  19. 19. Microscopic Structure Of MetalsMicroscopic Structure Of Metals  Most metals have crystalline structure in solidMost metals have crystalline structure in solid state which are held together by metallic bonds.state which are held together by metallic bonds.  Metals also exist in liquid state eg, Hg, in whichMetals also exist in liquid state eg, Hg, in which crystalline alignment is lost and the atoms movecrystalline alignment is lost and the atoms move freely in mass of liquid metal.freely in mass of liquid metal. www.indiandentalacademy.com
  20. 20. Metallic BondMetallic Bond  Primary BondsPrimary Bonds 1.1. Ionic BondsIonic Bonds 2.2. Covalent BondsCovalent Bonds 3.3. Metallic BondsMetallic Bonds  Secondary BondsSecondary Bonds Vander walls bondsVander walls bonds www.indiandentalacademy.com
  21. 21. Fabrication (Shaping) Methods OfFabrication (Shaping) Methods Of MetalsMetals  Casting – is the best and popular method.Casting – is the best and popular method.  Working on the metal – either in cold or hotWorking on the metal – either in cold or hot condition (i.e, with or without heating). Thiscondition (i.e, with or without heating). This involves pressing, rolling or forging. The metalinvolves pressing, rolling or forging. The metal subjected to the above process are called assubjected to the above process are called as wrought metals.wrought metals. www.indiandentalacademy.com
  22. 22. Fabrication (Shaping) Methods OfFabrication (Shaping) Methods Of Metals (Contd.)Metals (Contd.)  Extrusion - The process in which the metal isExtrusion - The process in which the metal is forced through a die to form a metal tubing.forced through a die to form a metal tubing.  Powder Metallurgy – involves pressingPowder Metallurgy – involves pressing powdered metals into a mould of desired shapepowdered metals into a mould of desired shape and heating it to a high temperature to cause aand heating it to a high temperature to cause a solid mass.solid mass. www.indiandentalacademy.com
  23. 23. Solidification Of Pure MetalSolidification Of Pure Metal  Pure metal has a melting point-known as FusionPure metal has a melting point-known as Fusion Temperature, and has specific heat.Temperature, and has specific heat.  To melt a crystalline substance (metal) someTo melt a crystalline substance (metal) some what more heat energy is required to convert itwhat more heat energy is required to convert it from solid to liquid.from solid to liquid.  This extra heat is stored away within the atomsThis extra heat is stored away within the atoms in the form of latent heat of fusion.in the form of latent heat of fusion. www.indiandentalacademy.com
  24. 24. Solidification Of Pure Metal (Contd.)Solidification Of Pure Metal (Contd.)  MechanismMechanism When the solid metal changes into liquid, itsWhen the solid metal changes into liquid, its crystalline pattern disappears, and the atoms arecrystalline pattern disappears, and the atoms are randomly distributed in the mass of liquid andrandomly distributed in the mass of liquid and they have more energy and are therefore movethey have more energy and are therefore move about freely.about freely.  In the reverse process of changing into solid,In the reverse process of changing into solid, temperature of the melt goes gradually (cooling);temperature of the melt goes gradually (cooling); atoms make an attempt to reform the crystallineatoms make an attempt to reform the crystalline arrangement.arrangement. www.indiandentalacademy.com
  25. 25. Mechanism of CrystallizationMechanism of Crystallization  A pure metal may crystallize in a tree-branchA pure metal may crystallize in a tree-branch pattern to form what is called a NUCLEUSpattern to form what is called a NUCLEUS  The initial nuclei are small in size and few inThe initial nuclei are small in size and few in number known as EMBRYO, which do notnumber known as EMBRYO, which do not stabilize in the melt and soon disappear.stabilize in the melt and soon disappear.  As the temperature of the metal gradually goesAs the temperature of the metal gradually goes down, a stable NUCLEUS is formed.down, a stable NUCLEUS is formed. www.indiandentalacademy.com
  26. 26. Mechanism of CrystallizationMechanism of Crystallization (contd.)(contd.)  A pure metal crystallizes from nuclei in a patternA pure metal crystallizes from nuclei in a pattern that often resembles the branches of a treethat often resembles the branches of a tree yielding crystals that are called dendritesyielding crystals that are called dendrites  Dental base metal casting alloys solidify with aDental base metal casting alloys solidify with a dendritic microstructuredendritic microstructure  The inter dendritic regions serves as sites forThe inter dendritic regions serves as sites for crack propagationcrack propagation www.indiandentalacademy.com
  27. 27. Mechanism of CrystallizationMechanism of Crystallization (contd.)(contd.)  Most noble metal casting alloys solidify with anMost noble metal casting alloys solidify with an equiaxed polycrystalline microstructureequiaxed polycrystalline microstructure  The metal is therefore made of thousands ofThe metal is therefore made of thousands of tiny crystals, such a metal is called polycrystallinetiny crystals, such a metal is called polycrystalline and each crystal in the structure is called aand each crystal in the structure is called a GRAIN.GRAIN. www.indiandentalacademy.com
  28. 28. Mechanism of CrystallizationMechanism of Crystallization (contd.)(contd.) www.indiandentalacademy.com
  29. 29. Importance of grain boundaryImportance of grain boundary  During permanent deformation of ductile dentalDuring permanent deformation of ductile dental alloys the dislocations cannot cross from onealloys the dislocations cannot cross from one grain to an adjacent grain and they willgrain to an adjacent grain and they will subsequently pile up at the grain boundaries.subsequently pile up at the grain boundaries. Hence further deformation in these regionsHence further deformation in these regions require greater stress.require greater stress.  Low melting phases precipitates and porosity areLow melting phases precipitates and porosity are typically found at grain boundaries of dentaltypically found at grain boundaries of dental casting alloys.casting alloys. www.indiandentalacademy.com
  30. 30. Control Of Grain SizeControl Of Grain Size  More nuclei in a given area results in smallerMore nuclei in a given area results in smaller grain size.grain size.  Rate of Crystallization – is faster than the rate ofRate of Crystallization – is faster than the rate of nuclei formation there will be larger grains.nuclei formation there will be larger grains.  Rate of Cooling –Rate of Cooling – Rapid cooling – Smaller grain sizeRapid cooling – Smaller grain size Slow cooling – Larger grain sizeSlow cooling – Larger grain size www.indiandentalacademy.com
  31. 31. Importance of grain sizeImportance of grain size  For noble metal casting alloys the yield strengthFor noble metal casting alloys the yield strength vary inversely with the square root of grain sizevary inversely with the square root of grain size  Compositional uniformity and corrosionCompositional uniformity and corrosion resistance of a cast dental alloy will be superiorresistance of a cast dental alloy will be superior for a fine grain sizefor a fine grain size www.indiandentalacademy.com
  32. 32. Crystal Space LatticeCrystal Space Lattice  The formed crystals in a metal are arranged in aThe formed crystals in a metal are arranged in a orderly pattern – layer by layer in regular stacks.orderly pattern – layer by layer in regular stacks.  The crystals of a metal is in the form of a spaceThe crystals of a metal is in the form of a space lattice.lattice.  The type of space lattice varies from metal toThe type of space lattice varies from metal to metal.metal. www.indiandentalacademy.com
  33. 33. Crystal Space LatticeCrystal Space Lattice www.indiandentalacademy.com
  34. 34. www.indiandentalacademy.com
  35. 35. Lattice Imperfections Or DefectsLattice Imperfections Or Defects  During crystal growth they do not meet inDuring crystal growth they do not meet in regular fashion lattice by lattice plane, they growregular fashion lattice by lattice plane, they grow randomly and meet irregularly resulting inrandomly and meet irregularly resulting in imperfection or defects.imperfection or defects.  These defects may be POINT DEFECTS orThese defects may be POINT DEFECTS or LINE DEFECTS.LINE DEFECTS.  The line defects are also DISLOCATIONS.The line defects are also DISLOCATIONS. www.indiandentalacademy.com
  36. 36. Edge Dislocation Slip PlaneEdge Dislocation Slip Plane  The line defects in a lattice can be made to slipThe line defects in a lattice can be made to slip by stress until finally the dislocation reaches theby stress until finally the dislocation reaches the edge of the metal and disappears. This is knownedge of the metal and disappears. This is known as EDGE DISLOCATION.as EDGE DISLOCATION.  The plane along which the dislocation moves isThe plane along which the dislocation moves is the slip lane.the slip lane. www.indiandentalacademy.com
  37. 37. Edge Dislocation Slip PlaneEdge Dislocation Slip Plane www.indiandentalacademy.com
  38. 38. Edge Dislocation Slip PlaneEdge Dislocation Slip Plane www.indiandentalacademy.com
  39. 39. Edge Dislocation and Slip PlaneEdge Dislocation and Slip Plane (Contd.)(Contd.)  The strength and ductility of the metal dependsThe strength and ductility of the metal depends to a large extent on the ease with whichto a large extent on the ease with which dislocations are able to movedislocations are able to move  If the dislocation impedes each other’sIf the dislocation impedes each other’s movement and metal becomes harder suchmovement and metal becomes harder such hardening is called WORK HARDENING orhardening is called WORK HARDENING or STRAIN HARDENING.STRAIN HARDENING. www.indiandentalacademy.com
  40. 40. Edge Dislocation and Slip PlaneEdge Dislocation and Slip Plane (Contd.)(Contd.)  If this is done at room temperature withoutIf this is done at room temperature without heating the metal it is called COLD WORKINGheating the metal it is called COLD WORKING and the finished metal is called WROUGHTand the finished metal is called WROUGHT METAL.METAL. www.indiandentalacademy.com
  41. 41. Cooling Pattern of Liquid MetalCooling Pattern of Liquid Metal During SolidificationDuring Solidification  Liquidus temperature – the temperature atLiquidus temperature – the temperature at which a metal in liquid state undergoes firstwhich a metal in liquid state undergoes first solidification.solidification.  Solidus temperature – the temperature at whichSolidus temperature – the temperature at which the last liquid of the metal solidifies.the last liquid of the metal solidifies. www.indiandentalacademy.com
  42. 42. Cooling Pattern of Liquid MetalCooling Pattern of Liquid Metal During SolidificationDuring Solidification www.indiandentalacademy.com
  43. 43. www.indiandentalacademy.com
  44. 44. Working On MetalsWorking On Metals  Deformation of Metal – Cold WorkDeformation of Metal – Cold Work –– Hot WorkHot Work –– ElasticElastic – Permanent– Permanent • AnnealingAnnealing • Fracture of the metalFracture of the metal www.indiandentalacademy.com
  45. 45. Working On Metals (Contd.)Working On Metals (Contd.)  Cold Work – when a metal is worked uponCold Work – when a metal is worked upon without heating.without heating.  Hot Work – when a metal is worked uponHot Work – when a metal is worked upon without heating.without heating.  Working on metal involves rolling, bending,Working on metal involves rolling, bending, pulling, pressing, hammering, etc in order topulling, pressing, hammering, etc in order to give a certain shape to a metal.give a certain shape to a metal.  At the end of such a work the metal becomesAt the end of such a work the metal becomes wrought.wrought. www.indiandentalacademy.com
  46. 46. Working On Metals (Contd.)Working On Metals (Contd.)  Cold working results inCold working results in • Increased surface hardness, strength andIncreased surface hardness, strength and proportional limit.proportional limit. • Decreased ductility, resistance to corrosion andDecreased ductility, resistance to corrosion and distorted grain structure.distorted grain structure. www.indiandentalacademy.com
  47. 47. Working On Metals (Contd.)Working On Metals (Contd.)  Annealing – heat treatment of metal or glass toAnnealing – heat treatment of metal or glass to eliminate the undesirable effects of straineliminate the undesirable effects of strain hardening and return the metal to its originalhardening and return the metal to its original condition without changing its shape.condition without changing its shape.  It involves three steps,It involves three steps, 1.1. RecoveryRecovery 2.2. RecrystallizationRecrystallization 3.3. Grain growthGrain growth www.indiandentalacademy.com
  48. 48. RecoveryRecovery  During recovery, cold work properties begin toDuring recovery, cold work properties begin to disappear.disappear. www.indiandentalacademy.com
  49. 49. RecrystallizationRecrystallization  The temperature at which the Old grainsThe temperature at which the Old grains disappear completely and are replaced by newdisappear completely and are replaced by new set of strain free grains is called recrystallization .set of strain free grains is called recrystallization .  The metal gets back its original soft and ductileThe metal gets back its original soft and ductile nature.nature. www.indiandentalacademy.com
  50. 50. Grain GrowthGrain Growth  Grain growth stops when a coarse grainGrain growth stops when a coarse grain structure is reached.structure is reached. www.indiandentalacademy.com
  51. 51. AnnealingAnnealing www.indiandentalacademy.com
  52. 52. Fracture Of MetalFracture Of Metal  If cold work is continued then the metalIf cold work is continued then the metal eventually fractures.eventually fractures.  This may be ,This may be ,  Trans granular – through the crystals and occursTrans granular – through the crystals and occurs at room temperature.at room temperature.  Inter granular – in-between the crystals andInter granular – in-between the crystals and occurs at elevated temperatures.occurs at elevated temperatures. www.indiandentalacademy.com
  53. 53. ALLOYSALLOYS  Combination of two or more metals which areCombination of two or more metals which are generally mutually soluble in the liquidgenerally mutually soluble in the liquid condition.condition.  A metallic material formed by the intimateA metallic material formed by the intimate blending of 2 or more metals some times a non-blending of 2 or more metals some times a non- metal be added.metal be added.  A substance composed of 2or more elements atA substance composed of 2or more elements at least one of which is a metal.least one of which is a metal. www.indiandentalacademy.com
  54. 54. Methods of AlloyingMethods of Alloying  By melting together the base metal (main) andBy melting together the base metal (main) and the alloying element, mixing them thoroughly,the alloying element, mixing them thoroughly, and allowing the mixture to cool and solidify.and allowing the mixture to cool and solidify. This is a common method.This is a common method.  Sintering or by powder metallurgy. Metals areSintering or by powder metallurgy. Metals are powdered, mixed and pressed to the desiredpowdered, mixed and pressed to the desired shape and then heated but not melted till theshape and then heated but not melted till the powders unite to form a solid mass.powders unite to form a solid mass. www.indiandentalacademy.com
  55. 55. Objectives of AlloyingObjectives of Alloying 1.1. To increase hardness and strength.To increase hardness and strength. 2.2. To lower the melting point.To lower the melting point. 3.3. To increase fluidity of liquid metal.To increase fluidity of liquid metal. 4.4. To increase resistance to tarnish and corrosion.To increase resistance to tarnish and corrosion. www.indiandentalacademy.com
  56. 56. Objectives of Alloying (Contd.)Objectives of Alloying (Contd.) 5.5. To make casting or working on the metal easy.To make casting or working on the metal easy. 6.6. To change the microscopic structure of theTo change the microscopic structure of the metal.metal. 7.7. To change the color of the metal.To change the color of the metal. 8.8. To provide special electrical and magneticTo provide special electrical and magnetic properties.properties. www.indiandentalacademy.com
  57. 57. Types of AlloysTypes of Alloys  Ferrous alloys - in which iron is the base metalFerrous alloys - in which iron is the base metal and its alloy is stainless steel.and its alloy is stainless steel.  Gold and silver alloys - with added copper toGold and silver alloys - with added copper to increase hardness, e.g. jewellery gold.increase hardness, e.g. jewellery gold.  Fusible alloys - which have low meltingFusible alloys - which have low melting temperature. Lead is the main metal, e.g. solder,temperature. Lead is the main metal, e.g. solder, valves of pressure cooker.valves of pressure cooker. www.indiandentalacademy.com
  58. 58. Types of Alloys (Contd.)Types of Alloys (Contd.)  Die-casting alloys-zinc containing aluminum andDie-casting alloys-zinc containing aluminum and magnesium - e.g. car spare parts, door handles.magnesium - e.g. car spare parts, door handles.  Babbit metal (named after Mr. Isaac Babbit ofBabbit metal (named after Mr. Isaac Babbit of Boston)-tin or lead based alloys-e.g. bearings.Boston)-tin or lead based alloys-e.g. bearings.  Nickel alloys - to make coins "Monel".Nickel alloys - to make coins "Monel". www.indiandentalacademy.com
  59. 59. Classification Of AlloysClassification Of Alloys  On the basis of number of metalsOn the basis of number of metals present in anpresent in an alloy.alloy.  Binary - alloy of two constituents.Binary - alloy of two constituents.  Ternary - alloy of three constituents.Ternary - alloy of three constituents.  Quaternary - alloy of four constituents.Quaternary - alloy of four constituents.  Quinary - alloy of five constituents.Quinary - alloy of five constituents. www.indiandentalacademy.com
  60. 60. Classification Of Alloys (Contd.)Classification Of Alloys (Contd.)  On the basis of miscibility (solubility) of atomsOn the basis of miscibility (solubility) of atoms of the ingredient metals after solidification i.e, inof the ingredient metals after solidification i.e, in the solid state. The four possibilities are,the solid state. The four possibilities are, Solid solutionSolid solution Eutectic mixtureEutectic mixture Inter metallic compoundInter metallic compound Peritectic alloyPeritectic alloy www.indiandentalacademy.com
  61. 61. Solid SolutionSolid Solution  Complete solubility.Complete solubility.  These are the alloys in which the ingredient metals areThese are the alloys in which the ingredient metals are soluble in each other both in liquid state as well as insoluble in each other both in liquid state as well as in solid state, e.g. gold and copper alloy.solid state, e.g. gold and copper alloy.  These are the alloys in which alloying atoms areThese are the alloys in which alloying atoms are distributed throughout the crystals without causing adistributed throughout the crystals without causing a fundamental change in the shape of the parent spacefundamental change in the shape of the parent space lattice, and also the microscopic structure islattice, and also the microscopic structure is homogeneous and resembles that of pure metal.homogeneous and resembles that of pure metal. www.indiandentalacademy.com
  62. 62. Solid SolutionSolid Solution www.indiandentalacademy.com
  63. 63. Solid Solution (Contd.)Solid Solution (Contd.)  Some examples of Solid solutions are,Some examples of Solid solutions are,  Au-Ag alloyAu-Ag alloy  Au-Cu alloyAu-Cu alloy  Au-Pt alloyAu-Pt alloy  Au-Pa alloyAu-Pa alloy  Ag-Pd alloy, etc.Ag-Pd alloy, etc.  Solid solution alloys consist of single phase only and areSolid solution alloys consist of single phase only and are chemically homogenous.chemically homogenous. www.indiandentalacademy.com
  64. 64. Solid Solution (Contd.)Solid Solution (Contd.)  The solid-solution alloys may be;The solid-solution alloys may be; 1.1. SUBSTITUTIONAL SOLID SOLUTIONSUBSTITUTIONAL SOLID SOLUTION ALLOYALLOY - the- the atoms of one metal replaces theatoms of one metal replaces the atoms of parent metal in the space lattice andatoms of parent metal in the space lattice and occupies that place. Such a substitutional solidoccupies that place. Such a substitutional solid solution alloy can have TWO TYPES of latticesolution alloy can have TWO TYPES of lattice arrangement.arrangement. www.indiandentalacademy.com
  65. 65. Solid Solution (Contd.)Solid Solution (Contd.) a.a. ORDERED ARRANGEMENTORDERED ARRANGEMENT  This produces an ordered space lattice.This produces an ordered space lattice.  In this arrangement two types of metal atomsIn this arrangement two types of metal atoms occupy very specific or ordered (as if) positionsoccupy very specific or ordered (as if) positions within the crystal, resulting in specificwithin the crystal, resulting in specific properties.properties.  This produces a super lattice within the solidThis produces a super lattice within the solid solution, which may distort the original lattice.solution, which may distort the original lattice. This type of change occurs with gold copperThis type of change occurs with gold copper alloys during heat treatments.alloys during heat treatments. www.indiandentalacademy.com
  66. 66. Solid Solution (Contd.)Solid Solution (Contd.)  DISORDERED ARRANGEMENTDISORDERED ARRANGEMENT This produces disordered space lattice if theThis produces disordered space lattice if the atoms of both the metals are randomlyatoms of both the metals are randomly distributed in the space lattice.distributed in the space lattice. www.indiandentalacademy.com
  67. 67. DISORDERED ARRANGEMENTDISORDERED ARRANGEMENT www.indiandentalacademy.com
  68. 68. Solid Solution (Contd.)Solid Solution (Contd.)  INTERSTITIAL SOLID SOLUTION ALLOYINTERSTITIAL SOLID SOLUTION ALLOY The atoms of one metal do not replace theThe atoms of one metal do not replace the parent atom in a space lattice, insteadparent atom in a space lattice, instead occupy a space existing in between theoccupy a space existing in between the atoms of the parent metalatoms of the parent metal.. This can only happen if the atom of theThis can only happen if the atom of the alloying element is sufficiently small to fitalloying element is sufficiently small to fit into the spaces between the atoms of theinto the spaces between the atoms of the parent metal.parent metal. www.indiandentalacademy.com
  69. 69. Conditions Favoring Solid-SolubilityConditions Favoring Solid-Solubility  Atom size - if the atom sizes of the mixing metalAtom size - if the atom sizes of the mixing metal are same, it will produce solid solution type ofare same, it will produce solid solution type of alloy.alloy.  Valency - metals of the same valency willValency - metals of the same valency will produce solid-solution alloy.produce solid-solution alloy.  Space-lattice type - if same, preferably if faceSpace-lattice type - if same, preferably if face centered will favour solid solubility.centered will favour solid solubility.  Chemical affinity - must be less to produceChemical affinity - must be less to produce solid-solution alloy.solid-solution alloy. www.indiandentalacademy.com
  70. 70. Properties Of Solid-solution Type OfProperties Of Solid-solution Type Of AlloysAlloys  Strong and hard.Strong and hard.  High proportional limit.High proportional limit.  High tensile strength.High tensile strength.  More ductility and malleability.More ductility and malleability.  Have a melting range instead of point.Have a melting range instead of point.  Can be burnished and worked easily.Can be burnished and worked easily.  High resistance to tarnish and corrosion.High resistance to tarnish and corrosion. www.indiandentalacademy.com
  71. 71. Eutectic AlloysEutectic Alloys  Complete in-solubility in solid state.Complete in-solubility in solid state.  The ingredient metals are soluble in each otherThe ingredient metals are soluble in each other in liquid state, but separate out (precipitate) asin liquid state, but separate out (precipitate) as different layers in solid state.different layers in solid state.  Example, silver and copper alloy.Example, silver and copper alloy. www.indiandentalacademy.com
  72. 72. Eutectic AlloysEutectic Alloys www.indiandentalacademy.com
  73. 73. Eutectic Alloys (Contd.)Eutectic Alloys (Contd.)  In this type of alloy, there is one particularIn this type of alloy, there is one particular composition at which it behaves similar to purecomposition at which it behaves similar to pure metal-that is; it solidifies at a constantmetal-that is; it solidifies at a constant temperature (or a melting point) instead of atemperature (or a melting point) instead of a range.range.  Alloys with a composition less than that ofAlloys with a composition less than that of eutectic are hypoeutectic and alloys with aeutectic are hypoeutectic and alloys with a composition more than eutectic are calledcomposition more than eutectic are called hypereutectichypereutectic www.indiandentalacademy.com
  74. 74. Eutectic Alloys (Contd.)Eutectic Alloys (Contd.)  These alloys are called eutectic because theThese alloys are called eutectic because the temperature at which this occurs is lower thantemperature at which this occurs is lower than the fusion temperature of either constituentthe fusion temperature of either constituent metals.metals.  Example, Ag-72 per cent and Cu-28 per centExample, Ag-72 per cent and Cu-28 per cent www.indiandentalacademy.com
  75. 75. Eutectic Alloys (Contd.)Eutectic Alloys (Contd.)  Properties – BrittleProperties – Brittle Less strongLess strong Less resistance to corrosionLess resistance to corrosion www.indiandentalacademy.com
  76. 76. Inter metallic CompoundsInter metallic Compounds  Inter metallic compounds are those when theInter metallic compounds are those when the metals are soluble in the liquid state but unitemetals are soluble in the liquid state but unite and form a chemical compound on solidifying.and form a chemical compound on solidifying.  They are called inter metallic compoundsThey are called inter metallic compounds because the alloy is formed by a chemicalbecause the alloy is formed by a chemical reaction between a metal and metal.reaction between a metal and metal. www.indiandentalacademy.com
  77. 77. Inter metallic Compounds (Contd.)Inter metallic Compounds (Contd.)  Very hard and brittle.Very hard and brittle.  Properties do not resemble the properties ofProperties do not resemble the properties of their parent metals.their parent metals. www.indiandentalacademy.com
  78. 78. Peritectic AlloysPeritectic Alloys  E.g. Platinum-Silver in casting alloyE.g. Platinum-Silver in casting alloy  Limited solid solubility of 2 metals can result inLimited solid solubility of 2 metals can result in transformation referred as Peritectictransformation referred as Peritectic  More BrittleMore Brittle  Reduced corrosion resistanceReduced corrosion resistance www.indiandentalacademy.com
  79. 79. Heat TreatmentHeat Treatment  Heat treatment (not melting) of metals in theHeat treatment (not melting) of metals in the solid state is called SOLID STATEsolid state is called SOLID STATE REACTIONS.REACTIONS.  This is a method to cause diffusion of atoms ofThis is a method to cause diffusion of atoms of the alloy by heating a solid metal to a certainthe alloy by heating a solid metal to a certain temperature and for certain period of time.temperature and for certain period of time.  This will result in. the changes in theThis will result in. the changes in the microscopic structure and physical properties.microscopic structure and physical properties. www.indiandentalacademy.com
  80. 80. Heat Treatment (Contd.)Heat Treatment (Contd.)  Important criteria in this process are:Important criteria in this process are: 1.1. Composition of alloyComposition of alloy 2.2. Temperature to which it is heatedTemperature to which it is heated 3.3. Time of heatingTime of heating 4.4. Method of cooling - cooling slowly inMethod of cooling - cooling slowly in the air or quenching rapidly in coldthe air or quenching rapidly in cold water.water. www.indiandentalacademy.com
  81. 81. Purpose of Heat TreatmentPurpose of Heat Treatment  Shaping and working on the appliance in theShaping and working on the appliance in the laboratory is made easy when the alloy is soft.laboratory is made easy when the alloy is soft. This is the first stage and is called softening heatThis is the first stage and is called softening heat treatment.treatment.  To harden the alloy for oral use, so that it willTo harden the alloy for oral use, so that it will withstand oral stresses. The alloy is again heatedwithstand oral stresses. The alloy is again heated and this time it is called hardening heatand this time it is called hardening heat treatment.treatment. www.indiandentalacademy.com
  82. 82. Clinical significance of heatClinical significance of heat treatmenttreatment  Type I and II gold alloys usually do not hardenType I and II gold alloys usually do not harden or they harden to a lesser degree than do theor they harden to a lesser degree than do the types III and IV gold alloys.types III and IV gold alloys.  The mechanism of hardening is the result ofThe mechanism of hardening is the result of several different solid state transformationsseveral different solid state transformations  The type III and IV gold alloys that can beThe type III and IV gold alloys that can be hardened or strengthened from quenching, canhardened or strengthened from quenching, can also be softened by heat treatments.also be softened by heat treatments. www.indiandentalacademy.com
  83. 83. Types of Heat TreatmentTypes of Heat Treatment  Softening Heat treatmentSoftening Heat treatment  Hardening Heat treatmentHardening Heat treatment  Solution Heat treatmentSolution Heat treatment  Age HardeningAge Hardening www.indiandentalacademy.com
  84. 84. Softening heat treatment  Also known as ANNEALING. This is done forAlso known as ANNEALING. This is done for structures which are cold worked.structures which are cold worked.  TechniqueTechnique -- alloyalloy is placed in an electric furnaceis placed in an electric furnace at a temperature of 700°C for 10 minutes andat a temperature of 700°C for 10 minutes and then rapidly cooled (quenched).then rapidly cooled (quenched). www.indiandentalacademy.com
  85. 85. Softening heat treatment(Contd.)  Result of this is reduction in strength, hardnessResult of this is reduction in strength, hardness and pro­portional limit but increase in ductility.and pro­portional limit but increase in ductility. In other words the metal becomes soft. This isIn other words the metal becomes soft. This is also known as HOMOGENIZATIONalso known as HOMOGENIZATION TREATMENT.TREATMENT. www.indiandentalacademy.com
  86. 86. Hardening heat treatment  This is done for cast removable partialThis is done for cast removable partial dentures, saddles, bridges, but not fordentures, saddles, bridges, but not for Inlays.Inlays.  TechniqueTechnique -- The appliance (alloy) is heatThe appliance (alloy) is heat soaked at a temperature between 200-soaked at a temperature between 200- 450°C for 15-30 minutes and then rapidly450°C for 15-30 minutes and then rapidly cooled by quenching.cooled by quenching. www.indiandentalacademy.com
  87. 87. Hardening heat treatment(Contd.)  The result of this is increase in strength,The result of this is increase in strength, hardness and proportional limit but reduction inhardness and proportional limit but reduction in ductility.ductility.  Also known as ORDER HARDENINGAlso known as ORDER HARDENING oror PRECIPITATION HARDENINGPRECIPITATION HARDENING.. www.indiandentalacademy.com
  88. 88. Solution Heat Treatment Or Solution-Hardening  When the alloy is heat soaked, any precipitationsWhen the alloy is heat soaked, any precipitations formed during earlier heat treatment, will nowformed during earlier heat treatment, will now once again become soluble in the solvent metal.once again become soluble in the solvent metal.  Technique is same as softening heat treatment.Technique is same as softening heat treatment. www.indiandentalacademy.com
  89. 89. Age Hardening  After solution heat treatment, the alloy is onceAfter solution heat treatment, the alloy is once again heated to bring about further precipitationagain heated to bring about further precipitation and this time it shows in the metallography as aand this time it shows in the metallography as a fine dispersed phase.fine dispersed phase.  This also causes hardening of the alloy and isThis also causes hardening of the alloy and is known as age hardening because the alloy willknown as age hardening because the alloy will maintain its quality for many years.maintain its quality for many years. www.indiandentalacademy.com
  90. 90. Clinical significance of heatClinical significance of heat treatments in metal ceramic alloystreatments in metal ceramic alloys  Type I very high noble metal alloys with 96% toType I very high noble metal alloys with 96% to 98% noble alloys contains iron which is added as98% noble alloys contains iron which is added as a strengthening element.a strengthening element.  Iron reacts with platinum to form FePt3Iron reacts with platinum to form FePt3 precipitates, which strengthens the alloys.precipitates, which strengthens the alloys.  The optimum heat treatment is 30 minutes ;atThe optimum heat treatment is 30 minutes ;at 550o c which results in a 30% to 50% increase550o c which results in a 30% to 50% increase in the tensile strength.in the tensile strength. www.indiandentalacademy.com
  91. 91. Clinical significance of heatClinical significance of heat treatments in metal ceramic alloystreatments in metal ceramic alloys  In type III high noble metal alloys withIn type III high noble metal alloys with moderate silver alloys there is decrease in goldmoderate silver alloys there is decrease in gold which is made up by an increase in the palladiumwhich is made up by an increase in the palladium concentration to 26% to 31% plus an increase inconcentration to 26% to 31% plus an increase in the silver to 14% to 16%.the silver to 14% to 16%.  Neither of these alloys contain iron or platinumNeither of these alloys contain iron or platinum and both are strengthened mainly by a solidand both are strengthened mainly by a solid solution – hardening mechanism.solution – hardening mechanism. www.indiandentalacademy.com
  92. 92. Different Metals Used In DentistryDifferent Metals Used In Dentistry Gold (Au)Gold (Au)  noble metalnoble metal  provides a high level of corrosion and tarnish resistanceprovides a high level of corrosion and tarnish resistance  increases an alloy's melting range slightly.increases an alloy's melting range slightly.  improves workability, burnish ability, and raises the densityimproves workability, burnish ability, and raises the density  imparts a very pleasing yellow color to an alloy (if presentimparts a very pleasing yellow color to an alloy (if present in sufficient quantity).in sufficient quantity).  Unfortunately, that yellow color is readily offset by theUnfortunately, that yellow color is readily offset by the addition of "white" metals, such as palladium and silver.addition of "white" metals, such as palladium and silver. www.indiandentalacademy.com
  93. 93. PalladiumPalladium  Palladium, a member of the platinum group, is a noblePalladium, a member of the platinum group, is a noble metalmetal  Palladium is added to increase the strength, hardness (withPalladium is added to increase the strength, hardness (with copper), corrosion and tarnish resistance of gold-basedcopper), corrosion and tarnish resistance of gold-based alloys.alloys.  Palladium elevates an alloy's melting range and improvePalladium elevates an alloy's melting range and improve its sag resistance.its sag resistance.  Has a very strong whitening effect, so an alloy with 90%Has a very strong whitening effect, so an alloy with 90% gold and only 10% palladium will appear platinum-colored.gold and only 10% palladium will appear platinum-colored.  Palladium possesses a high affinity for hydrogen, oxygen,Palladium possesses a high affinity for hydrogen, oxygen, and carbon.and carbon.  It lowers the den­sity of the gold-based alloys slightly butIt lowers the den­sity of the gold-based alloys slightly but has little similar effect on silver-based metals.has little similar effect on silver-based metals. www.indiandentalacademy.com
  94. 94. PlatinumPlatinum  Platinum is a member of the platinum groupPlatinum is a member of the platinum group and is a noble metaland is a noble metal  Platinum increases the strength, meltingPlatinum increases the strength, melting range, and hardness of gold-based alloysrange, and hardness of gold-based alloys while improving their corrosion, tarnish, andwhile improving their corrosion, tarnish, and sag resistance.sag resistance.  It whitens an alloy and increases the densityIt whitens an alloy and increases the density of non gold-based metals because of its highof non gold-based metals because of its high density.density. www.indiandentalacademy.com
  95. 95. IridiumIridium  Iridium is a member of the platinum groupIridium is a member of the platinum group and is a noble metal.and is a noble metal.  serves as a grain refiner for gold- andserves as a grain refiner for gold- and palladium-based alloys to improve thepalladium-based alloys to improve the mechanical properties as well as the tarnishmechanical properties as well as the tarnish resistance.resistance. www.indiandentalacademy.com
  96. 96. Ruthenium (Ru)Ruthenium (Ru)  Ruthenium is a member of the palladiumRuthenium is a member of the palladium group and is a noble metal.group and is a noble metal.  Ruthenium acts as a grain refiner for gold-Ruthenium acts as a grain refiner for gold- and palladium- based alloys to improve theirand palladium- based alloys to improve their mechanical properties and tarnish resistancemechanical properties and tarnish resistance (like iridium).(like iridium). www.indiandentalacademy.com
  97. 97. SilverSilver  Although silver is a precious element, it is notAlthough silver is a precious element, it is not universally regarded as noble in the oral cavity .universally regarded as noble in the oral cavity .  Silver lowers the melting range, improves fluidity,Silver lowers the melting range, improves fluidity, and helps to control the coefficient of thermaland helps to control the coefficient of thermal expansion in gold- and palladium-based alloysexpansion in gold- and palladium-based alloys  Silver-containing porcelain alloys have beenSilver-containing porcelain alloys have been known to induce discolor­ation (yellow, brown, orknown to induce discolor­ation (yellow, brown, or green) with some porcelains.green) with some porcelains. www.indiandentalacademy.com
  98. 98. Silver (Contd)Silver (Contd)  Silver possesses a high affinity for oxygenSilver possesses a high affinity for oxygen absorption, which can lead to castingabsorption, which can lead to casting porosity and/or gassing.porosity and/or gassing.  However, small amounts of zinc or indiumHowever, small amounts of zinc or indium added to gold- and silver-based alloys helpadded to gold- and silver-based alloys help to control silver's absorption of oxygen.to control silver's absorption of oxygen.  Silver will also corrode and tarnish in theSilver will also corrode and tarnish in the presence of sulfur.presence of sulfur. www.indiandentalacademy.com
  99. 99. AluminiumAluminium  Aluminum is added to lower the melting range ofAluminum is added to lower the melting range of nickel-based alloys.nickel-based alloys.  Aluminum is a hardening agent and influencesAluminum is a hardening agent and influences oxide formation.oxide formation.  With the cobalt - chromium alloys used for metalWith the cobalt - chromium alloys used for metal ceramic restorations, aluminum is one of theceramic restorations, aluminum is one of the elements that is "etched" from the alloy's surfaceelements that is "etched" from the alloy's surface to create micromechanical reten­tion for resin-to create micromechanical reten­tion for resin- bonded retainers (Maryland Bridges).bonded retainers (Maryland Bridges). www.indiandentalacademy.com
  100. 100. BerylliumBeryllium  Like aluminum, beryllium lowers the meltingLike aluminum, beryllium lowers the melting range of nickel-based alloys, improves castability,range of nickel-based alloys, improves castability, improves polishability, is a hardener, and helps toimproves polishability, is a hardener, and helps to control oxide formation.control oxide formation.  The etching of nickel-chromium-beryllium alloysThe etching of nickel-chromium-beryllium alloys removes a Ni-Be phase to create the microremoves a Ni-Be phase to create the micro retention so important to the etched metal resin-retention so important to the etched metal resin- bonded retainer.bonded retainer.  potential health risks to both technicians andpotential health risks to both technicians and patients associ­ated with beryllium-containingpatients associ­ated with beryllium-containing alloys .alloys . www.indiandentalacademy.com
  101. 101. BoronBoron  Boron is a deoxidizer.Boron is a deoxidizer.  For nickel-based alloys, it is a hardening agent andFor nickel-based alloys, it is a hardening agent and an element that reduces the surface tension of thean element that reduces the surface tension of the molten alloy to improve castability.molten alloy to improve castability.  The nickel-chromium beryllium-free alloys thatThe nickel-chromium beryllium-free alloys that contain boron will pool on melting, as opposed tocontain boron will pool on melting, as opposed to the Ni-Cr-Be alloys that do not pool.the Ni-Cr-Be alloys that do not pool.  Boron also acts to reduce ductility and to increaseBoron also acts to reduce ductility and to increase hardness.hardness. www.indiandentalacademy.com
  102. 102. Chromium (Cr)Chromium (Cr)  Chromium is a solid solution hardeningChromium is a solid solution hardening agent that contributes to corrosionagent that contributes to corrosion resistance by its passivating nature in nickel-resistance by its passivating nature in nickel- and cobalt-based alloys.and cobalt-based alloys. www.indiandentalacademy.com
  103. 103. CobaltCobalt (Co)(Co)  Cobalt is an alternative to the nickel-basedCobalt is an alternative to the nickel-based alloys, but the cobalt-based metals are morealloys, but the cobalt-based metals are more difficult to process.difficult to process.  Cobalt is included in some high-palladiumCobalt is included in some high-palladium alloys to increase the alloy's coefficient ofalloys to increase the alloy's coefficient of thermal expansion and to act as athermal expansion and to act as a strengthener .strengthener . www.indiandentalacademy.com
  104. 104. Copper (Cu)Copper (Cu)  Copper serves as a hardening and strengtheningCopper serves as a hardening and strengthening agentagent  Lower the melting range of an alloy, and interactsLower the melting range of an alloy, and interacts with platinum, palladium, silver, and gold towith platinum, palladium, silver, and gold to provide a heat-treating capability in gold, silver,provide a heat-treating capability in gold, silver, and palladium-based alloys.and palladium-based alloys.  Copper helps to form an oxide for porcelainCopper helps to form an oxide for porcelain bonding, lowers the density slightly, and canbonding, lowers the density slightly, and can enhance passivity in the high palladium-copperenhance passivity in the high palladium-copper alloys.alloys. www.indiandentalacademy.com
  105. 105. GalliumGallium (Ga)(Ga)  Gallium is added to silver-free porcelainGallium is added to silver-free porcelain alloys to compensate for the decreasedalloys to compensate for the decreased coefficient of thermal expansion created bycoefficient of thermal expansion created by the removal of silver.the removal of silver.  Concerns over silver's potential to discolorConcerns over silver's potential to discolor dental porcelain have greatly limited its usedental porcelain have greatly limited its use in systems other than palladium-silverin systems other than palladium-silver www.indiandentalacademy.com
  106. 106. IndiumIndium  Serves many functions in gold-based metalServes many functions in gold-based metal ceramic alloys.ceramic alloys.  It is a less volatile oxide-scavenging agent (toIt is a less volatile oxide-scavenging agent (to protect molten alloy);protect molten alloy);  lowers the alloy's melting range and density;lowers the alloy's melting range and density; improves fluidity;improves fluidity;  Has a strengthening effect. Indium is added to nonHas a strengthening effect. Indium is added to non gold­based alloy systems to form an oxide layer forgold­based alloy systems to form an oxide layer for porce­lain bonding.porce­lain bonding.  Alloys with a high silver content (eg, palladium-Alloys with a high silver content (eg, palladium- silver) rely on indium to enhance tarnishsilver) rely on indium to enhance tarnish resistance.resistance. www.indiandentalacademy.com
  107. 107. Iron (Fe)Iron (Fe)  Iron is added to some gold-based porcelainIron is added to some gold-based porcelain systems for hardening and oxide production.systems for hardening and oxide production.  Iron is included in a few base metal alloys asIron is included in a few base metal alloys as well.well. www.indiandentalacademy.com
  108. 108. Manganese (Mn)Manganese (Mn)  Manganese is an oxide scavenger and aManganese is an oxide scavenger and a hardening agent in nickel- and cobalt-basedhardening agent in nickel- and cobalt-based alloys.alloys. www.indiandentalacademy.com
  109. 109. Molybdenum (Mo)Molybdenum (Mo)  Molybdenum improves corrosion resistance,Molybdenum improves corrosion resistance, influences oxide production, and is helpfulinfluences oxide production, and is helpful in adjusting the coefficient of thermalin adjusting the coefficient of thermal expansion of nickel-based alloys.expansion of nickel-based alloys. www.indiandentalacademy.com
  110. 110. Nickel (Ni)Nickel (Ni)  Nickel has been selected as a base for porcelainNickel has been selected as a base for porcelain alloys because its coefficient of thermal expansionalloys because its coefficient of thermal expansion approximates that of gold and it providesapproximates that of gold and it provides resistance to corrosion.resistance to corrosion.  Unfortunately, nickel is a sensitizer and a knownUnfortunately, nickel is a sensitizer and a known carcinogen.carcinogen.  Estimates of nickel sensitivity among women inEstimates of nickel sensitivity among women in the United States range from 9% to 31.9% and fromthe United States range from 9% to 31.9% and from 0.8% to 20.7% among men .0.8% to 20.7% among men . www.indiandentalacademy.com
  111. 111. Tin (Sn)Tin (Sn)  Tin is a hardening agent that acts to lowerTin is a hardening agent that acts to lower the melting range of an alloy.the melting range of an alloy.  It also assists in oxide production forIt also assists in oxide production for porcelain bonding in gold- and palladium-porcelain bonding in gold- and palladium- based alloys.based alloys.  Tin is one of the key trace elements forTin is one of the key trace elements for oxidation of the palladium-silver alloys.oxidation of the palladium-silver alloys. www.indiandentalacademy.com
  112. 112. Titanium (Ti)Titanium (Ti)  Like aluminum and beryllium, titanium isLike aluminum and beryllium, titanium is added to lower the melting range andadded to lower the melting range and improve castability.improve castability.  Titanium also acts as a hardener andTitanium also acts as a hardener and influences oxide formation at highinfluences oxide formation at high temperatures.temperatures. www.indiandentalacademy.com
  113. 113. Zinc (Zn)Zinc (Zn)  Zinc helps lower the melting range of anZinc helps lower the melting range of an alloy and acts as a deoxidizer or scavengeralloy and acts as a deoxidizer or scavenger to combine with other oxides.to combine with other oxides.  Zinc improves the castability of an alloy andZinc improves the castability of an alloy and contributes to hardness when combinedcontributes to hardness when combined with palladium.with palladium. www.indiandentalacademy.com
  114. 114. Need For Dental casting alloysNeed For Dental casting alloys  The Major factors areThe Major factors are  Economy – To perform the same functionEconomy – To perform the same function but at the lower costbut at the lower cost  Performance – To perform better in ease ofPerformance – To perform better in ease of processing, improved handing characters,processing, improved handing characters, and increased fracture resistanceand increased fracture resistance  Esthetics –To provide more esthetic resultsEsthetics –To provide more esthetic results such as increased translucencysuch as increased translucency www.indiandentalacademy.com
  115. 115. Historical Perspective On DentalHistorical Perspective On Dental Casting AlloysCasting Alloys  The history of dental casting alloys has beenThe history of dental casting alloys has been influenced by three major factors.influenced by three major factors.  1. The technological changes of dental1. The technological changes of dental prosthesisprosthesis  2. Metallurgical advancement2. Metallurgical advancement  3. Price changes of noble metals since 1968.3. Price changes of noble metals since 1968. www.indiandentalacademy.com
  116. 116. Historical Perspective On DentalHistorical Perspective On Dental Casting Alloys (contd)Casting Alloys (contd)  Taggarts presentation to the New YorkTaggarts presentation to the New York odontological group in 1907 on the fabrication ofodontological group in 1907 on the fabrication of cast inlay restorations often has beencast inlay restorations often has been acknowledged as the first reported application ofacknowledged as the first reported application of the lost wax technique in dentistry.the lost wax technique in dentistry.  The inlay technique described by Taggarat was anThe inlay technique described by Taggarat was an instant‘ success. It soon led to the casting ofinstant‘ success. It soon led to the casting of complex inlays such as on lays, crowns, fixedcomplex inlays such as on lays, crowns, fixed partial dentures and removable partial denturepartial dentures and removable partial denture frame works.frame works. www.indiandentalacademy.com
  117. 117. Historical Perspective On DentalHistorical Perspective On Dental Casting Alloys (contd)Casting Alloys (contd)  Because pure gold did not have the physicalBecause pure gold did not have the physical properties required for these dental restorationsproperties required for these dental restorations alloys were quickly adopted. These gold werealloys were quickly adopted. These gold were further strengthened with Cu, Ag, or Pt.further strengthened with Cu, Ag, or Pt.  1932, the dental materials group at the national1932, the dental materials group at the national Bureau of standards surveyed the alloys being usedBureau of standards surveyed the alloys being used and roughly classified them as Type I, Type II,and roughly classified them as Type I, Type II, Type III & Type IV.Type III & Type IV. www.indiandentalacademy.com
  118. 118. Historical Perspective On DentalHistorical Perspective On Dental Casting Alloys (contd)Casting Alloys (contd)  At that time some tarnish tests indicatedAt that time some tarnish tests indicated that alloys with a gold content lower thanthat alloys with a gold content lower than 65% to 75% tarnished too readily for dental65% to 75% tarnished too readily for dental useuse  By 1948, the composition of dental nobleBy 1948, the composition of dental noble metal alloys for cast metal restorations hasmetal alloys for cast metal restorations has become rather diverse with thesebecome rather diverse with these formulations, the tarnishing tendency of theformulations, the tarnishing tendency of the original alloys apparently had disappeared.original alloys apparently had disappeared. www.indiandentalacademy.com
  119. 119. Historical Perspective On DentalHistorical Perspective On Dental Casting Alloys (contd)Casting Alloys (contd)  The base metal removable partial denture wereThe base metal removable partial denture were introduced in1930's.introduced in1930's.  In late 1950's a breakthrough occurred in dentalIn late 1950's a breakthrough occurred in dental technology that was to influence significantly thetechnology that was to influence significantly the fabrication of dental restorations. This was thefabrication of dental restorations. This was the successful veneering of metal substrate with dentalsuccessful veneering of metal substrate with dental porcelain.porcelain.  In 1978 the price of gold was climbing so rapidlyIn 1978 the price of gold was climbing so rapidly that attention focused on the noble metal alloys tothat attention focused on the noble metal alloys to reduce the precious metal content get retain thereduce the precious metal content get retain the advantage of noble metal for dental use.advantage of noble metal for dental use. www.indiandentalacademy.com
  120. 120. www.indiandentalacademy.com
  121. 121. Desirable Properties Of CastingDesirable Properties Of Casting Alloys: The metals must exhibitAlloys: The metals must exhibit  11. Bio compatibility. Bio compatibility  2. Ease of melting & casting2. Ease of melting & casting  3. Ease of brazing and soldering & polishing3. Ease of brazing and soldering & polishing  4. Little solidification shrinkage.4. Little solidification shrinkage.  5. Minimal reactivity with mould material.5. Minimal reactivity with mould material.  6. Good wear resistance.6. Good wear resistance. www.indiandentalacademy.com
  122. 122. Desirable Properties Of CastingDesirable Properties Of Casting Alloys: The metals must exhibitAlloys: The metals must exhibit  7. High strength7. High strength  8. Sag resistance8. Sag resistance  9. Tarnish & corrosion resistance.9. Tarnish & corrosion resistance.  10.Alergenic components in casting alloys10.Alergenic components in casting alloys  11.Economic considerations11.Economic considerations  12. Lab cost12. Lab cost www.indiandentalacademy.com
  123. 123. Alloys type by function - 1932Alloys type by function - 1932 Type I gold alloysType I gold alloys Soft (VHN 50 TO 90)Soft (VHN 50 TO 90) Type II gold alloysType II gold alloys Medium (90 TO 120)Medium (90 TO 120) Type III gold alloysType III gold alloys Hard (120 TO 150)Hard (120 TO 150) Type IV gold alloysType IV gold alloys Extra Hard (more than 150)Extra Hard (more than 150) www.indiandentalacademy.com
  124. 124. Alloy type by functionAlloy type by function  Type I ;- small inlays easily burnished andType I ;- small inlays easily burnished and subject to very slight stresssubject to very slight stress  Type II;- inlays subject to moderate stressType II;- inlays subject to moderate stress thick three quarter crowns, abutmentsthick three quarter crowns, abutments pontics and full crownspontics and full crowns  Type III;- short span fixed partial denturesType III;- short span fixed partial dentures  Type IV;- long span fixed partial denturesType IV;- long span fixed partial dentures www.indiandentalacademy.com
  125. 125. Classification Of Alloys By ADA 1984Classification Of Alloys By ADA 1984 Alloy TypeAlloy Type Total Noble contentTotal Noble content High noble metalHigh noble metal >=40 wt% of Au and 60%>=40 wt% of Au and 60% wt ofwt of noble metalnoble metal elementselements Noble metalNoble metal >=25 wt% of noble metal>=25 wt% of noble metal Predominantly basePredominantly base metalmetal <25 wt% of the noble<25 wt% of the noble metal elementsmetal elements www.indiandentalacademy.com
  126. 126. Alloy classification based on color orAlloy classification based on color or compositioncomposition According to their color and principalAccording to their color and principal element or elements (Phillips, 1982).element or elements (Phillips, 1982).  Yellow golds-Yellow golds- yellowyellow color, with greater than 60%color, with greater than 60% gold contentgold content  White golds-White golds- whitewhite color, but with more thancolor, but with more than 50% gold content50% gold content www.indiandentalacademy.com
  127. 127. Alloy classification based on color orAlloy classification based on color or composition (Cond..)composition (Cond..)  Low (or economy) golds-Low (or economy) golds- usually yellow colored, with lessusually yellow colored, with less than 60% gold (usually 42% to 55%)than 60% gold (usually 42% to 55%)  High palladium –High palladium – white colored, with palladium thewhite colored, with palladium the major component; may contain small quantities ofmajor component; may contain small quantities of gold (2%) and a limited amount of either copper orgold (2%) and a limited amount of either copper or cobaltcobalt www.indiandentalacademy.com
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  132. 132. Metal Ceramic RestorationMetal Ceramic Restoration  By Definition – Partial crown, full crown orBy Definition – Partial crown, full crown or fixed partial denture made with a metalfixed partial denture made with a metal substrate to which porcelain is bonded forsubstrate to which porcelain is bonded for esthetic enhancement via an intermediateesthetic enhancement via an intermediate metal oxide layermetal oxide layer  Also called as porcelain fused metal ,Also called as porcelain fused metal , porcelain bonded to metal , porcelain toporcelain bonded to metal , porcelain to metal and ceramo metalmetal and ceramo metal www.indiandentalacademy.com
  133. 133. History of metal ceramic alloysHistory of metal ceramic alloys  1789 - The first porcelain tooth material was1789 - The first porcelain tooth material was patented inpatented in byby a French dentist (de Chemant) ina French dentist (de Chemant) in collaboration with a French pharmacistcollaboration with a French pharmacist (Duchateau). The product, was an improved(Duchateau). The product, was an improved versionversion ofof "mineral paste teeth“ that was"mineral paste teeth“ that was produced bproduced byy Duchateau in 1774 ,which wasDuchateau in 1774 ,which was introduced in England soon thereafterintroduced in England soon thereafter byby dede Chemant.Chemant. www.indiandentalacademy.com
  134. 134. History of metal ceramic alloysHistory of metal ceramic alloys  1808- Fonzi, an Italian dentist, invented a "terrometallic"1808- Fonzi, an Italian dentist, invented a "terrometallic" porcelain tooth that was held in placeporcelain tooth that was held in place byby a platinum pin or frame.a platinum pin or frame.  1817 - Planteau, a French dentist, introduced porcelain teeth to1817 - Planteau, a French dentist, introduced porcelain teeth to .the United States.the United States  1822 - Peale, an artist, developed a baking process in1822 - Peale, an artist, developed a baking process in Philadelphia for these teeth.Philadelphia for these teeth.  1825 -1825 - Commercial productionCommercial production ofof these teeth was started bythese teeth was started by Stockton.Stockton.  1837 - In England, Ash developed an improved version1837 - In England, Ash developed an improved version ofof thethe porcelain tooth.porcelain tooth.  1844, the nephew1844, the nephew ofof Stockton founded the S.S. White Company,Stockton founded the S.S. White Company, and this led to further refinementand this led to further refinement ofof the design and the massthe design and the mass productionproduction ofof porcelain denture teeth.porcelain denture teeth. www.indiandentalacademy.com
  135. 135. History of metal ceramic alloysHistory of metal ceramic alloys  1903 - Dr. Charles Land introduced one of the1903 - Dr. Charles Land introduced one of the first ceramic crowns to dentistry.first ceramic crowns to dentistry.  Land, described a technique for fabricatingLand, described a technique for fabricating ceramic crowns using a platinum foil matrix andceramic crowns using a platinum foil matrix and high-fusing felds­pathic porcelain.high-fusing felds­pathic porcelain.  These crowns exhibited excellent aesthetics; butThese crowns exhibited excellent aesthetics; but the low flexural strengththe low flexural strength ofof porcelain resulted inporcelain resulted in a high incidencea high incidence ofof failures.failures. www.indiandentalacademy.com
  136. 136. History of metal ceramic alloysHistory of metal ceramic alloys  1962 - Weinstein et al , responsible for the patents of1962 - Weinstein et al , responsible for the patents of long-standing aesthetic performance and clinicallong-standing aesthetic performance and clinical survivability of metal-ceramic restorations.survivability of metal-ceramic restorations.  One of these patents described the formulations ofOne of these patents described the formulations of feldspathic porcelain that allowed systematic control offeldspathic porcelain that allowed systematic control of the sintering temperature and thermal expansionthe sintering temperature and thermal expansion coefficient.coefficient.  The other patent described the components that couldThe other patent described the components that could be used to produce alloys that bonded chemically tobe used to produce alloys that bonded chemically to and were thermally compatible with feldspathicand were thermally compatible with feldspathic porcelains.porcelains.  The first commercial porcelain was developed by VitaThe first commercial porcelain was developed by Vita Zahnfabrik in about 1963Zahnfabrik in about 1963 www.indiandentalacademy.com
  137. 137. Requirements for metal ceramicRequirements for metal ceramic alloysalloys  The chief objection for the use of dental porcelain asThe chief objection for the use of dental porcelain as restorative material is its low strength under tensile andrestorative material is its low strength under tensile and shear, stress conditionsshear, stress conditions  A method by which this disadvantage can be minimized isA method by which this disadvantage can be minimized is to bond the porcelain directly to a cast alloy sub structureto bond the porcelain directly to a cast alloy sub structure made to fit the prepared toothmade to fit the prepared tooth  These alloys should have the potential to bond to the dentalThese alloys should have the potential to bond to the dental porcelainporcelain  Possess coefficient of thermal contraction compatible withPossess coefficient of thermal contraction compatible with that of dental porcelainthat of dental porcelain  Solidus temperature is sufficiently high to permit theSolidus temperature is sufficiently high to permit the aplication of low fusing porcelainaplication of low fusing porcelain www.indiandentalacademy.com
  138. 138. Metal – ceramic bondingMetal – ceramic bonding  Factors controlling metal ceramic adhesionFactors controlling metal ceramic adhesion areare  Formation of strong chemical bondingFormation of strong chemical bonding  Mechanical interlocking between twoMechanical interlocking between two materialsmaterials  Residual stressesResidual stresses www.indiandentalacademy.com
  139. 139. Chemical bondingChemical bonding  The original metal ceramic alloy containing 88%The original metal ceramic alloy containing 88% gold were too soft for stress bearing restorationsgold were too soft for stress bearing restorations since there was no chemical bond between alloysince there was no chemical bond between alloy and dental porcelain.and dental porcelain.  Mechanical retention and undercuts were used toMechanical retention and undercuts were used to prevent detachment of the ceramic veneer.prevent detachment of the ceramic veneer.  Since the bond strength of porcelain to this type ofSince the bond strength of porcelain to this type of alloy was less than the cohesive strength ofalloy was less than the cohesive strength of porcelain bond failures occurred at the metalporcelain bond failures occurred at the metal porcelain interface due to concentration of residualporcelain interface due to concentration of residual tensile stress at the metal ceramic interface .tensile stress at the metal ceramic interface . www.indiandentalacademy.com
  140. 140. Chemical bondingChemical bonding  The addition of 1% base metals to goldThe addition of 1% base metals to gold palladium and platinum alloys was sufficientpalladium and platinum alloys was sufficient to produce a slight oxide film on surface ofto produce a slight oxide film on surface of sub structure to achieve porcelain metalsub structure to achieve porcelain metal bond strength that surpassed the cohesivebond strength that surpassed the cohesive strength of porcelain. This new type of alloystrength of porcelain. This new type of alloy with small amounts of base metals addedwith small amounts of base metals added became the standards for metal ceramicbecame the standards for metal ceramic prostheses.prostheses. www.indiandentalacademy.com
  141. 141. Mechanical interlockingMechanical interlocking  Roughness or generally the topography ofRoughness or generally the topography of ceramic metal interface play a large part inceramic metal interface play a large part in adhesion. The ceramic penetrating into aadhesion. The ceramic penetrating into a rough metal surface can mechanically attachrough metal surface can mechanically attach to the metal, improving adhesion.to the metal, improving adhesion.  Roughness provides increased surface areaRoughness provides increased surface area for adhesion and more room for chemicalfor adhesion and more room for chemical bond to form.bond to form. www.indiandentalacademy.com
  142. 142. Mechanical interlockingMechanical interlocking  Roughness can reduce adhesion if ceramicRoughness can reduce adhesion if ceramic does not penetrate into the surface and voidsdoes not penetrate into the surface and voids are present at the interface; this may happenare present at the interface; this may happen with improperly fired porcelain or metalswith improperly fired porcelain or metals that are poorly wetted by the porcelain.that are poorly wetted by the porcelain.  Sandblasting is often used to roughen theSandblasting is often used to roughen the surface of the metal cooping to improve thesurface of the metal cooping to improve the bonding of the ceramic.bonding of the ceramic. www.indiandentalacademy.com
  143. 143. Thermal compatibilityThermal compatibility  Refers to the ability of a metal and its veneeringRefers to the ability of a metal and its veneering porcelain to contract at similar rates.porcelain to contract at similar rates.  The coefficient of thermal expansion by definitionThe coefficient of thermal expansion by definition is the change in length per unit of original lengthis the change in length per unit of original length of a material when its temperature is raised by 1o Kof a material when its temperature is raised by 1o K  When the co efficient of thermal expansion ofWhen the co efficient of thermal expansion of metal and porcelain are compatible the tensilemetal and porcelain are compatible the tensile stress that develop during cooling are insufficientstress that develop during cooling are insufficient to cause immediate cracking of porcelain orto cause immediate cracking of porcelain or delayed cracking after cooling at roomdelayed cracking after cooling at room temperature.temperature. www.indiandentalacademy.com
  144. 144. Thermal compatibilityThermal compatibility  If the porcelain has much larger coefficientIf the porcelain has much larger coefficient of contraction than that of metal, tensileof contraction than that of metal, tensile strength of porcelain may be exceeded sincestrength of porcelain may be exceeded since of large tensile stress causing crackof large tensile stress causing crack propagation in porcelain veneer.propagation in porcelain veneer.  If contraction coefficient of porcelain isIf contraction coefficient of porcelain is much lower than that of metal, failure levelmuch lower than that of metal, failure level stresses can occur at the metal porcelainstresses can occur at the metal porcelain interface.interface. www.indiandentalacademy.com
  145. 145. Thermal compatibilityThermal compatibility  Porcelains have coefficient of thermal expansionPorcelains have coefficient of thermal expansion between 13.0 and 14.0 X 10-6 and metal betweenbetween 13.0 and 14.0 X 10-6 and metal between 13.5 and 14.5 X 10-6.13.5 and 14.5 X 10-6.  The difference of 0.5 X10-6 in thermal expansionThe difference of 0.5 X10-6 in thermal expansion between metal and porcelain causes the metal tobetween metal and porcelain causes the metal to contract slightly more than does the ceramiccontract slightly more than does the ceramic during cooling after firing the porcelain.during cooling after firing the porcelain.  This puts the ceramic under slight residualThis puts the ceramic under slight residual compression which makes it less sensitive tocompression which makes it less sensitive to applied tensile forces.applied tensile forces. www.indiandentalacademy.com
  146. 146. Sag resistanceSag resistance  Coefficient of thermal expansion tends toCoefficient of thermal expansion tends to have a reciprocal relationship with thehave a reciprocal relationship with the melting point and range of alloysmelting point and range of alloys  Higher the melting temperature of metalHigher the melting temperature of metal lower its Coefficient of thermal expansionlower its Coefficient of thermal expansion  Metal ceramic alloys should have sufficientlyMetal ceramic alloys should have sufficiently high melting range to avoid sag deformationhigh melting range to avoid sag deformation or melting during sintering of porcelainor melting during sintering of porcelain veneer.veneer. www.indiandentalacademy.com
  147. 147. Selection of Metal Ceramic AlloysSelection of Metal Ceramic Alloys Physical properties includes..Physical properties includes.. ColorColor Noble Metal ContentNoble Metal Content HardnessHardness Yield StrengthYield Strength ElongationElongation Fusion TemperatureFusion Temperature www.indiandentalacademy.com
  148. 148. ColorColor  The most important obvious property of anThe most important obvious property of an alloy – Coloralloy – Color  Dentists prefer to have Gold color inDentists prefer to have Gold color in restorations which is compatible to the colorrestorations which is compatible to the color of porcelain than the dark color of baseof porcelain than the dark color of base metal alloys.metal alloys. www.indiandentalacademy.com
  149. 149. Noble Metal ContentNoble Metal Content Indirectly denotes…..Indirectly denotes…..  Corrosion resistance of the alloysCorrosion resistance of the alloys  Inert properties of the alloys which makes itInert properties of the alloys which makes it to tolerate oral fluids and not release anyto tolerate oral fluids and not release any harmful products into the oral environment.harmful products into the oral environment. www.indiandentalacademy.com
  150. 150. HardnessHardness  Definition - Resistance of material to plasticDefinition - Resistance of material to plastic deformationdeformation  Important in relation to occlusal wearImportant in relation to occlusal wear resistance and finishingresistance and finishing  affects polishing propertiesaffects polishing properties www.indiandentalacademy.com
  151. 151. Yield StrengthYield Strength  The stress at which a test specimen exhibitsThe stress at which a test specimen exhibits a specific amount of plastic straina specific amount of plastic strain  Necessary in determining Load BearingNecessary in determining Load Bearing ability especially in FPD , since crossability especially in FPD , since cross sectional area of metal used in PFMsectional area of metal used in PFM restoration are usually smaller than that ofrestoration are usually smaller than that of all metal restorationsall metal restorations www.indiandentalacademy.com
  152. 152. ElongationElongation  Maximum amount of plastic strain a tensileMaximum amount of plastic strain a tensile test specimen can sustain it fracturestest specimen can sustain it fractures  Related to Marginal finishing PropertiesRelated to Marginal finishing Properties especially in Partial veneer crown andespecially in Partial veneer crown and abutmentsabutments www.indiandentalacademy.com
  153. 153. Fusion TemperatureFusion Temperature  Temperature at which the metal solidifiesTemperature at which the metal solidifies  Important in relation to SAG Resistance as itImportant in relation to SAG Resistance as it is necessary for the alloy to withstandis necessary for the alloy to withstand temperatures of the porcelain firing cycle.temperatures of the porcelain firing cycle. www.indiandentalacademy.com
  154. 154. Chemical PropertiesChemical Properties  Tarnish and corrosion resistanceTarnish and corrosion resistance  Tarnish is a thin film of a surface deposit orTarnish is a thin film of a surface deposit or an interaction layer that is adherent to thean interaction layer that is adherent to the metal surface. E.g. these films are generallymetal surface. E.g. these films are generally found on gold alloys with relatively highfound on gold alloys with relatively high silver content or on silver alloys.silver content or on silver alloys. Selection of Metal Ceramic AlloysSelection of Metal Ceramic Alloys www.indiandentalacademy.com
  155. 155. Corrosion resistanceCorrosion resistance  Corrosion is the physical dissolution of a materialCorrosion is the physical dissolution of a material in an environment .in an environment .  corrosion resistance is derived from the materialcorrosion resistance is derived from the material components that being too noble to react in thecomponents that being too noble to react in the oral environment e.g. gold and palladium ororal environment e.g. gold and palladium or  By the ability of one or more of the metallicBy the ability of one or more of the metallic elements to form an adherent passivating surfaceelements to form an adherent passivating surface film, which inhibits any subsurface reactions Cr infilm, which inhibits any subsurface reactions Cr in Ni-Cr and Co-Cr alloys and titanium in Ti-6 Al- 4VNi-Cr and Co-Cr alloys and titanium in Ti-6 Al- 4V alloyalloy www.indiandentalacademy.com
  156. 156. Lab workability and Casting AccuracyLab workability and Casting Accuracy  To provide clinically acceptable castings byTo provide clinically acceptable castings by its ability to wet the investment moldits ability to wet the investment mold material and flow in to the most intricatematerial and flow in to the most intricate regions of the mold without any appreciableregions of the mold without any appreciable interaction with the investmentinteraction with the investment www.indiandentalacademy.com
  157. 157. Bio CompatibilityBio Compatibility Base metal alloys – Nickel (Ni) and Beryllium (Be)Base metal alloys – Nickel (Ni) and Beryllium (Be)  The occupational health and safety administrationThe occupational health and safety administration (OSHA) specifies that exposure to Beryllium dust(OSHA) specifies that exposure to Beryllium dust in air should be limited to a concentration of 2in air should be limited to a concentration of 2 ug /meter cubeug /meter cube  The allowable maximum concentration is 5 ugThe allowable maximum concentration is 5 ug /meter cube/meter cube  Sensitivity – Contact dermatitis with Nickel orSensitivity – Contact dermatitis with Nickel or Nickel containing alloysNickel containing alloys www.indiandentalacademy.com
  158. 158. CompositionComposition  Key factor since components of alloyKey factor since components of alloy influences color of porcelaininfluences color of porcelain  Can compromise esthetics of restorationsCan compromise esthetics of restorations  Silver-color change causes greening ofSilver-color change causes greening of porcelain which occurs by exchange of silverporcelain which occurs by exchange of silver from alloy and sodium from porcelainfrom alloy and sodium from porcelain  The color may vary from green, yellowThe color may vary from green, yellow green, yellow orange, orange and browngreen, yellow orange, orange and brown hueshues www.indiandentalacademy.com
  159. 159. Economic considerationsEconomic considerations  Cost of metals is major concern for the useCost of metals is major concern for the use of the alloys for metal ceramic restorations.of the alloys for metal ceramic restorations. www.indiandentalacademy.com
  160. 160. www.indiandentalacademy.com
  161. 161. High Gold AlloysHigh Gold Alloys  PFM introduced to dental profession withPFM introduced to dental profession with introduction of Caramco No : 1 alloy in 1958introduction of Caramco No : 1 alloy in 1958  Fore Runner of improved High Gold AlloysFore Runner of improved High Gold Alloys that remain as market today – Jelenko Othat remain as market today – Jelenko O  Composed principally of Gold and PlatinumComposed principally of Gold and Platinum groupgroup www.indiandentalacademy.com
  162. 162. High gold alloysHigh gold alloys  Gold content varies from 78% -87% by weight and nobleGold content varies from 78% -87% by weight and noble metal content is about 97%metal content is about 97%  Small amounts of tin, indium and iron are added forSmall amounts of tin, indium and iron are added for strength and to promote a good porcelain bond to the metalstrength and to promote a good porcelain bond to the metal oxideoxide  CostlyCostly  Light yellow in colorLight yellow in color  low tensile strength makes them a questionable choice forlow tensile strength makes them a questionable choice for fixed partial denturesfixed partial dentures  Hardness of alloys ideal for working characteristics andHardness of alloys ideal for working characteristics and ease of finishingease of finishing  Corrosion résistance is excellentCorrosion résistance is excellent www.indiandentalacademy.com
  163. 163. Gold,Platinum,Palladium AlloysGold,Platinum,Palladium Alloys  Composition ;-Composition ;-  Gold: 75%-88%Gold: 75%-88%  Platinum: up to 8%Platinum: up to 8%  Palladium: up to 11 %Palladium: up to 11 %  Silver: up to 5% (if present)Silver: up to 5% (if present)  Trace elements like indium, iron, and tin forTrace elements like indium, iron, and tin for porcelain bonding. (If the palladium contentporcelain bonding. (If the palladium content exceeds that of platinum, then the alloys should beexceeds that of platinum, then the alloys should be classified as Au-Pd-Pt.)classified as Au-Pd-Pt.) www.indiandentalacademy.com
  164. 164. Gold,Platinum,PalladiumGold,Platinum,Palladium Alloys(Contd)Alloys(Contd) AdvantagesAdvantages  Excellent castabilityExcellent castability  Excellent porcelain bondingExcellent porcelain bonding  Easy to adjust and finish High nobility levelEasy to adjust and finish High nobility level Excellent corrosion Advantages and tarnishExcellent corrosion Advantages and tarnish resistanceresistance  Biocompatible Some are yellow in colorBiocompatible Some are yellow in color  Not "technique sensitive"Not "technique sensitive"  BurnishableBurnishable www.indiandentalacademy.com
  165. 165. Gold,Platinum,Palladium AlloysGold,Platinum,Palladium Alloys (Contd)(Contd)  Disadvantages;-Disadvantages;-  High costHigh cost  Poor sag resistance so not suited for long-Poor sag resistance so not suited for long- span fixed partial denturesspan fixed partial dentures  Low hardness (greater wear)Low hardness (greater wear)  High density (fewer castings per ounce)High density (fewer castings per ounce) www.indiandentalacademy.com
  166. 166. Gold Palladium Silver AlloysGold Palladium Silver Alloys Introduced in 1970 as will ceram wIntroduced in 1970 as will ceram w composition -composition - Gold: 39%-53%Gold: 39%-53% Palladium:25%35%Palladium:25%35% Silver: 12%-22%Silver: 12%-22% Like the Au-Pt-Pd alloys, trace amounts ofLike the Au-Pt-Pd alloys, trace amounts of oxidizable elements are added for porcelainoxidizable elements are added for porcelain bondingbonding.. www.indiandentalacademy.com
  167. 167. Gold Palladium Silver AlloysGold Palladium Silver Alloys (Contd..)(Contd..) AdvantagesAdvantages  Less expensive than Au-Pt-Pd alloysLess expensive than Au-Pt-Pd alloys  Improved rigidity and sag resistanceImproved rigidity and sag resistance  High nobility levelHigh nobility level www.indiandentalacademy.com
  168. 168. Gold Palladium Silver AlloysGold Palladium Silver Alloys (Contd..)(Contd..) DisadvantagesDisadvantages  High silver content creates potential forHigh silver content creates potential for porcelain discolorationporcelain discoloration  High costHigh cost  High coefficient of thermal expansionHigh coefficient of thermal expansion  Tarnish and corrosion resistantTarnish and corrosion resistant www.indiandentalacademy.com
  169. 169. Gold-Palladium-Silver (low silverGold-Palladium-Silver (low silver group)group) CompositionComposition  Gold – 52% - 77%Gold – 52% - 77%  Palladium – 10% - 33%Palladium – 10% - 33%  Silver – 5% - 12%Silver – 5% - 12% Trace amounts of oxidizable elements forTrace amounts of oxidizable elements for porcelein bondingporcelein bonding www.indiandentalacademy.com
  170. 170. Gold-Palladium-Silver (low silverGold-Palladium-Silver (low silver group)group)  AdvantagesAdvantages  Less expensive than Au-Pt-Pd alloysLess expensive than Au-Pt-Pd alloys  Improved sag resistanceImproved sag resistance  High noble metal contentHigh noble metal content  Tarnish and corrosion resistantTarnish and corrosion resistant www.indiandentalacademy.com
  171. 171. Gold-Palladium-Silver (low silverGold-Palladium-Silver (low silver group)group)  DisadvantagesDisadvantages  High costHigh cost  High coefficient of thermal expansionHigh coefficient of thermal expansion  Silver creates potential for porcelainSilver creates potential for porcelain discoloration (but less than high-silverdiscoloration (but less than high-silver group)group) www.indiandentalacademy.com
  172. 172. Gold-Palladium alloysGold-Palladium alloys CompositionComposition  Gold – 44% -55%Gold – 44% -55%  Palladium – 35% - 45%Palladium – 35% - 45%  Gallium up to 5%Gallium up to 5%  Iridium and tin up to 8% - 12%Iridium and tin up to 8% - 12% Iridium and tin are the oxidizable elementsIridium and tin are the oxidizable elements responsible for porcelain bondingresponsible for porcelain bonding www.indiandentalacademy.com
  173. 173. Gold-Palladium alloysGold-Palladium alloys AdvantagesAdvantages  Excellent castabilityExcellent castability  Good bond strengthGood bond strength  Improved strength (sag resistance)Improved strength (sag resistance)  Improved HardnessImproved Hardness  Tarnish and corrosion resistantTarnish and corrosion resistant  Lower densityLower density www.indiandentalacademy.com
  174. 174. Gold-Palladium alloysGold-Palladium alloys DisadvantagesDisadvantages  High costHigh cost  Not thermally compatible with highNot thermally compatible with high expansion dental porcelainsexpansion dental porcelains www.indiandentalacademy.com
  175. 175. Palladium-Silver alloysPalladium-Silver alloys CompositionComposition  Palladium – 55% - 60%Palladium – 55% - 60%  Silver – 28% - 30%Silver – 28% - 30% Indium and tinIndium and tin  Palladium – 50% - 55%Palladium – 50% - 55%  Silver – 35% - 40%Silver – 35% - 40% Tin (little or no Indium)Tin (little or no Indium) Trace elements of other oxidizable base elementsTrace elements of other oxidizable base elements are also presentare also present www.indiandentalacademy.com
  176. 176. Palladium-Silver alloys (contd)Palladium-Silver alloys (contd) AdvantagesAdvantages  Good castability (whenGood castability (when torch casting)torch casting)  Good porcelainGood porcelain bondingbonding  Excellent sagExcellent sag resistance)resistance)  Low HardnessLow Hardness  BurnishabilityBurnishability  Good tarnish andGood tarnish and corrosion resistantcorrosion resistant  Low densityLow density  Low costLow cost  Moderate nobility levelModerate nobility level  Suitable for long-spanSuitable for long-span fixed partial denturesfixed partial dentures www.indiandentalacademy.com
  177. 177. Palladium-Silver alloys (contd)Palladium-Silver alloys (contd) DisadvantagesDisadvantages  High coefficient of thermalHigh coefficient of thermal expansionexpansion  Discoloration (yellow,Discoloration (yellow, brown, or green) maybrown, or green) may occur with some dentaloccur with some dental porcelainsporcelains  Some castability problemsSome castability problems  Pd and Ag prone to absorbPd and Ag prone to absorb gasesgases  Require regular purging ofRequire regular purging of the porcelain furnacethe porcelain furnace  May form internal oxidesMay form internal oxides  Should not be cast in aShould not be cast in a carbon cruciblecarbon crucible  Non carbon phosphateNon carbon phosphate bonded investmentsbonded investments recommendedrecommended www.indiandentalacademy.com
  178. 178. Palladium-cobalt alloysPalladium-cobalt alloys CompositionComposition  Palladium: 78%-88%Palladium: 78%-88%  Cobalt: 4%-10%Cobalt: 4%-10% (some high palladium-cobalt alloys may contain 2%(some high palladium-cobalt alloys may contain 2% gold)gold) Note:Note: Trace amounts of oxidizable elements (such asTrace amounts of oxidizable elements (such as gallium and indium) are added for porcelaingallium and indium) are added for porcelain bonding.bonding. www.indiandentalacademy.com
  179. 179. Palladium-cobalt alloysPalladium-cobalt alloys AdvantagesAdvantages  Low costLow cost  Reportedly good sag resistanceReportedly good sag resistance  Low density means moreLow density means more castings per ouncecastings per ounce (than gold-based alloys) Some melt and cast(than gold-based alloys) Some melt and cast easily Good polishabilityeasily Good polishability (supposed to be similar(supposed to be similar to Au-Pd alloys)to Au-Pd alloys)  Reportedly easier to presolder than high Pd-CuReportedly easier to presolder than high Pd-Cu alloysalloys www.indiandentalacademy.com
  180. 180. Palladium-cobalt alloysPalladium-cobalt alloys DisadvantagesDisadvantages  More compatible with higher expansionMore compatible with higher expansion porcelainsporcelains  Some are more prone toSome are more prone to over-heatingover-heating than high Pd-Cu Produce a thick, darkthan high Pd-Cu Produce a thick, dark oxide Colored oxide layer may causeoxide Colored oxide layer may cause bluing of porcelainbluing of porcelain  Prone to gas absorption Little informationProne to gas absorption Little information on long-term clinical successon long-term clinical success www.indiandentalacademy.com
  181. 181. High Palladium-Silver-Gold alloysHigh Palladium-Silver-Gold alloys CompositionComposition  Palladium: 75%-86%Palladium: 75%-86%  Silver: less than 1 %-7%Silver: less than 1 %-7%  Gold: 2%-6%Gold: 2%-6%  Platinum: less than 1.0% (if present)Platinum: less than 1.0% (if present) Trace amounts of oxidizabJe elements such asTrace amounts of oxidizabJe elements such as indium and gallium.indium and gallium. www.indiandentalacademy.com
  182. 182. High Palladium-Silver-Gold alloysHigh Palladium-Silver-Gold alloys  AdvantagesAdvantages  Low costLow cost  Low densityLow density  Improved sag resistance (better highImproved sag resistance (better high temperature strength)temperature strength)  Light-colored oxide layerLight-colored oxide layer www.indiandentalacademy.com
  183. 183. High Palladium-Silver-Gold alloysHigh Palladium-Silver-Gold alloys DisadvantagesDisadvantages  A relatively new alloy groupA relatively new alloy group  No data on long-term performanceNo data on long-term performance  Like other palladium-based alloys are proneLike other palladium-based alloys are prone to gaseous absorptionto gaseous absorption  Should not be cast in carbon cruciblesShould not be cast in carbon crucibles www.indiandentalacademy.com

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