Alloys used in metal ceramics /academy of fixed orthodontics

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Alloys used in metal ceramics /academy of fixed orthodontics

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. ALLOYS USED IN METALALLOYS USED IN METAL CERAMICSCERAMICS www.indiandentalacademy.com
  3. 3. 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
  4. 4. 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
  5. 5. 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 propertiesis responsible for many of the properties of metals-electrical and ther­mal conductivity,of metals-electrical and ther­mal conductivity, metallic luster, and (usually) high strengthmetallic luster, and (usually) high strength www.indiandentalacademy.com
  6. 6. www.indiandentalacademy.com
  7. 7. 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
  8. 8. 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
  9. 9. 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
  10. 10. Noble MetalNoble Metal  Noble Metal is one whose compounds areNoble Metal is one whose compounds are decomposable by heat alone at adecomposable by heat alone at a temperature not exceeding that of redness.temperature not exceeding that of redness.  They are corrosion and oxidation resistantThey are corrosion and oxidation resistant because of inertness and chemicalbecause of inertness and chemical resistance.resistance.  8 Noble metals used in dentistry are Au,8 Noble metals used in dentistry are Au, Pt, Pd, Ir, Os, Rh, Ru, Ag.Pt, Pd, Ir, Os, Rh, Ru, Ag.www.indiandentalacademy.com
  11. 11. 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
  12. 12. 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. 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
  13. 13. Another Classification OfAnother Classification Of MetalsMetals  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.,High Ductile and Malleable metal – e.g., Au.Au. www.indiandentalacademy.com
  14. 14. Microscopic Structure OfMicroscopic Structure Of MetalsMetals  Most metals have crystalline structure inMost metals have crystalline structure in solid state which are held together bysolid state which are held together by metallic bonds.metallic bonds.  Metals also exist in liquid state eg, Hg, inMetals also exist in liquid state eg, Hg, in which crystalline alignment is lost and thewhich crystalline alignment is lost and the atoms move freely in mass of liquid metal.atoms move freely in mass of liquid metal. www.indiandentalacademy.com
  15. 15. 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 vaal’s bondsVander vaal’s bonds www.indiandentalacademy.com
  16. 16. 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
  17. 17. 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
  18. 18. 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
  19. 19. 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
  20. 20. 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
  21. 21. Mechanism of CrystallizationMechanism of Crystallization (contd.)(contd.)  Such nucleus formations are calledSuch nucleus formations are called DENDRITES.DENDRITES.  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
  22. 22. Mechanism of CrystallizationMechanism of Crystallization (contd.)(contd.) www.indiandentalacademy.com
  23. 23. 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
  24. 24. 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
  25. 25. Crystal Space LatticeCrystal Space Lattice www.indiandentalacademy.com
  26. 26. www.indiandentalacademy.com
  27. 27. 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
  28. 28. 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
  29. 29. Edge Dislocation Slip PlaneEdge Dislocation Slip Plane www.indiandentalacademy.com
  30. 30. Edge Dislocation Slip PlaneEdge Dislocation Slip Plane www.indiandentalacademy.com
  31. 31. 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
  32. 32. 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
  33. 33. 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
  34. 34. Cooling Pattern of Liquid MetalCooling Pattern of Liquid Metal During SolidificationDuring Solidification www.indiandentalacademy.com
  35. 35. 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
  36. 36. 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
  37. 37. 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
  38. 38. 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
  39. 39. RecoveryRecovery  During recovery, cold work properties begin toDuring recovery, cold work properties begin to disappear.disappear. www.indiandentalacademy.com
  40. 40. 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
  41. 41. 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
  42. 42. AnnealingAnnealing www.indiandentalacademy.com
  43. 43. 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
  44. 44. 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
  45. 45. 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
  46. 46. 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
  47. 47. 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
  48. 48. 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
  49. 49. 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
  50. 50. 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
  51. 51. 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
  52. 52. 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
  53. 53. Solid SolutionSolid Solution www.indiandentalacademy.com
  54. 54. 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
  55. 55. 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
  56. 56. Solid Solution (Contd.)Solid Solution (Contd.) • ORDERED ARRANGEMENTORDERED ARRANGEMENT  This produces an ordered space lattice.This produces an ordered space lattice.  In this arrangement two types of metalIn this arrangement two types of metal atoms occupy very specific or ordered (asatoms occupy very specific or ordered (as if) positions within the crystal, resulting inif) positions within the crystal, resulting in specific properties.specific properties.  This produces a super lattice within theThis produces a super lattice within the solid solution, which may distort thesolid solution, which may distort the original lattice. This type of change occursoriginal lattice. This type of change occurs with gold copper alloys during heatwith gold copper alloys during heat treatments.treatments. www.indiandentalacademy.com
  57. 57. 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
  58. 58. DISORDERED ARRANGEMENTDISORDERED ARRANGEMENT www.indiandentalacademy.com
  59. 59. 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
  60. 60. 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
  61. 61. 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
  62. 62. 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
  63. 63. Eutectic AlloysEutectic Alloys www.indiandentalacademy.com
  64. 64. 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
  65. 65. 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
  66. 66. Eutectic Alloys (Contd.)Eutectic Alloys (Contd.)  Properties – BrittleProperties – Brittle Less strongLess strong Less resistance to corrosionLess resistance to corrosion www.indiandentalacademy.com
  67. 67. 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
  68. 68. 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
  69. 69. 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
  70. 70. 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
  71. 71. 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
  72. 72. 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
  73. 73. 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
  74. 74. 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
  75. 75. 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
  76. 76. 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
  77. 77. 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
  78. 78. 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
  79. 79. 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
  80. 80. Different Metals Used In DentistryDifferent Metals Used In Dentistry Gold (Au)Gold (Au)  Gold provides a high level of corrosion and tarnish resistanceGold provides a high level of corrosion and tarnish resistance  increases an alloy's melting range slightly.increases an alloy's melting range slightly.  Gold improves workability, burnish ability, and raises theGold improves workability, burnish ability, and raises the density .density .  However, gold imparts a very pleasing yellow color to an alloy (ifHowever, gold imparts a very pleasing yellow color to an alloy (if present in sufficient quantity).present in sufficient quantity).  Unfortunately, that yellow color is readily offset by the additionUnfortunately, that yellow color is readily offset by the addition of "white" metals, such as palladium and silver. Gold is a nobleof "white" metals, such as palladium and silver. Gold is a noble metal.metal. www.indiandentalacademy.com
  81. 81. PalladiumPalladium  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 will also elevate an alloy's melting range andPalladium will also elevate an alloy's melting range and improve its sag resistance.improve its sag resistance.  It has a very strong whitening effect, so an alloy with 90%It 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 but hasIt lowers the den­sity of the gold-based alloys slightly but has little similar effect on silver-based metals. Palladium, alittle similar effect on silver-based metals. Palladium, a member of the platinum group, is a noble metalmember of the platinum group, is a noble metal www.indiandentalacademy.com
  82. 82. PlatinumPlatinum  Platinum increases the strength, melting range,Platinum increases the strength, melting range, and hardness of gold-based alloys whileand hardness of gold-based alloys while improving their corrosion, tarnish, and sagimproving their corrosion, tarnish, and sag resistance.resistance.  It whitens an alloy and increases the density ofIt whitens an alloy and increases the density of non gold-based metals because of its highnon gold-based metals because of its high density.density.  Platinum is a member of the platinum groupPlatinum is a member of the platinum group and is a noble metaland is a noble metal www.indiandentalacademy.com
  83. 83. IridiumIridium  serves as a grain refiner for gold- and palladium-serves as a grain refiner for gold- and palladium- based alloys to improve the mechanicalbased alloys to improve the mechanical properties as well as the tarnish resistance.properties as well as the tarnish resistance.  Iridium is a member of the platinum group andIridium is a member of the platinum group and is a noble metal.is a noble metal. www.indiandentalacademy.com
  84. 84. Ruthenium (Ru)Ruthenium (Ru)  Ruthenium acts as a grain refiner for gold- andRuthenium acts as a grain refiner for gold- and palladium- based alloys to improve theirpalladium- based alloys to improve their mechanical properties and tarnish resistance (likemechanical properties and tarnish resistance (like iridium).iridium).  Ruthenium is a member of the palladium groupRuthenium is a member of the palladium group and is a noble metal.and is a noble metal. www.indiandentalacademy.com
  85. 85. SilverSilver  Silver lowers the melting range, improvesSilver lowers the melting range, improves fluidity, and helps to control the coefficient offluidity, and helps to control the coefficient of thermal expansion in gold- and palladium-basedthermal expansion in gold- and palladium-based alloysalloys  Silver-containing porcelain alloys have beenSilver-containing porcelain alloys have been known to induce discolor­ation (yellow, brown,known to induce discolor­ation (yellow, brown, or green) with some porcelains.or green) with some porcelains. www.indiandentalacademy.com
  86. 86. Silver (Contd)Silver (Contd)  Silver possesses a high affinity for oxygen absorp­tion,Silver possesses a high affinity for oxygen absorp­tion, which can lead to casting porosity and/or gas­sing.which can lead to casting porosity and/or gas­sing.  However, small amounts of zinc or indium added toHowever, small amounts of zinc or indium added to gold- and silver-based alloys help to control silver'sgold- and silver-based alloys help to control silver's absorption of oxygen.absorption of oxygen.  Silver will also corrode and tarnish in the presence ofSilver will also corrode and tarnish in the presence of sulfur. Although silver is a precious element, it is notsulfur. Although silver is a precious element, it is not universally regarded as noble in the oral cavity .universally regarded as noble in the oral cavity . www.indiandentalacademy.com
  87. 87. AluminiumAluminium  Aluminum is added to lower the melting rangeAluminum is added to lower the melting range of nickel-based alloys.of 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 forWith the cobalt - chromium alloys used for metal ceramic restorations, aluminum is one ofmetal ceramic restorations, aluminum is one of the elements that is "etched" from the alloy'sthe elements that is "etched" from the alloy's surface to create micromechanical reten­tion forsurface to create micromechanical reten­tion for resin-bonded retainers (Maryland Bridges).resin-bonded retainers (Maryland Bridges). www.indiandentalacademy.com
  88. 88. BerylliumBeryllium  Like aluminum, beryllium lowers the melting range ofLike aluminum, beryllium lowers the melting range of nickel-based alloys, improves castability, improvesnickel-based alloys, improves castability, improves polishability, is a hardener, and helps to control oxidepolishability, is a hardener, and helps to control oxide formation.formation.  The etching of nickel-chromium-beryllium alloysThe etching of nickel-chromium-beryllium alloys removes a Ni-Be phase to create the micro re­tentionremoves a Ni-Be phase to create the micro re­tention so important to the etched metal resin-bonded retainer.so important to the etched metal resin-bonded retainer.  Questions have been raised as to potential health risksQuestions have been raised as to potential health risks to both technicians and patients associ­ated withto both technicians and patients associ­ated with beryllium-containing alloys .beryllium-containing alloys . www.indiandentalacademy.com
  89. 89. BoronBoron  Boron is a deoxidizer.Boron is a deoxidizer.  For nickel-based alloys, it is a hardening agentFor nickel-based alloys, it is a hardening agent and an element that reduces the surface tensionand an element that reduces the surface tension of the molten alloy to improve castability.of the 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 opposedcontain boron will pool on melting, as opposed to the Ni-Cr-Be alloys that do not pool.to the Ni-Cr-Be alloys that do not pool.  Boron also acts to reduce ductility and toBoron also acts to reduce ductility and to increase hardness.increase hardness. www.indiandentalacademy.com
  90. 90. Chromium (Cr)Chromium (Cr)  Chromium is a solid solution hardening agentChromium is a solid solution hardening agent that contributes to corrosion resistance by itsthat contributes to corrosion resistance by its passivating nature in nickel- and cobalt-basedpassivating nature in nickel- and cobalt-based alloys.alloys. www.indiandentalacademy.com
  91. 91. 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 a strengthenerthermal expansion and to act as a strengthener www.indiandentalacademy.com
  92. 92. Copper (Cu)Copper (Cu)  Copper serves as a hardening and strengtheningCopper serves as a hardening and strengthening agent, can lower the melting range of an alloy,agent, can lower the melting range of an alloy, and interacts with platinum, palladium, silver,and interacts with platinum, palladium, silver, and gold to provide a heat-treating capability inand gold to provide a heat-treating capability in gold-, silver-, and palladium-based alloys.gold-, silver-, 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
  93. 93. GalliumGallium (Ga)(Ga)  Gallium is added to silver-free porcelain alloysGallium is added to silver-free porcelain alloys to compensate for the decreased coefficient ofto compensate for the decreased coefficient of thermal expansion created by the removal ofthermal expansion created by the removal of silver. (Concerns over silver's potential tosilver. (Concerns over silver's potential to discolor dental porcelain have greatly limited itsdiscolor dental porcelain have greatly limited its use in systems other than palladium-silver )use in systems other than palladium-silver ) www.indiandentalacademy.com
  94. 94. IndiumIndium  Indium serves many functions in gold-based metalIndium serves many functions in gold-based metal ceramic alloys.ceramic alloys.  It is a less volatile oxide-scavenging agent (to protectIt is a less volatile oxide-scavenging agent (to protect molten alloy);molten alloy);  lowers the alloy's melting range and density; improveslowers the alloy's melting range and density; improves fluidity;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-silver)Alloys with a high silver content (eg, palladium-silver) rely on indium to enhance tarnish resistance.rely on indium to enhance tarnish resistance. www.indiandentalacademy.com
  95. 95. 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
  96. 96. 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
  97. 97. Molybdenum (Mo)Molybdenum (Mo)  Molybdenum improves corrosion resistance,Molybdenum improves corrosion resistance, influ­ences oxide production, and is helpful ininflu­ences oxide production, and is helpful in adjusting the coefficient of thermal expansion ofadjusting the coefficient of thermal expansion of nickel-based alloys.nickel-based alloys. www.indiandentalacademy.com
  98. 98. 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 thermalalloys because its coefficient of thermal expansion approximates that of gold and itexpansion approximates that of gold and it provides resistance to corrosion.provides 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% andthe United States range from 9% to 31.9% and from 0.8% to 20.7% among men .from 0.8% to 20.7% among men . www.indiandentalacademy.com
  99. 99. Tin (Sn)Tin (Sn)  Tin is a hardening agent that acts to lower theTin is a hardening agent that acts to lower the melting range of an alloy. It also assists in oxidemelting range of an alloy. It also assists in oxide production for porcelain bonding in gold- andproduction for porcelain bonding in gold- and palladium-based al­loys. Tin is one of the keypalladium-based al­loys. Tin is one of the key trace elements for oxidation of the palladium-trace elements for oxidation of the palladium- silver alloys.silver alloys. www.indiandentalacademy.com
  100. 100. Titanium (Ti)Titanium (Ti)  Like aluminum and beryllium, titanium is addedLike aluminum and beryllium, titanium is added to lower the melting range and improveto lower the melting range and improve castability.castability.  Tita­nium also acts as a hardener and influencesTita­nium also acts as a hardener and influences oxide formation at high temperatures.oxide formation at high temperatures. www.indiandentalacademy.com
  101. 101. Zinc (Zn)Zinc (Zn)  Zinc helps lower the melting range of an alloyZinc helps lower the melting range of an alloy and acts as a deoxidizer or scavenger to combineand acts as a deoxidizer or scavenger to combine with other oxides.with other oxides.  Zinc improves the castability of an alloy andZinc improves the castability of an alloy and contributes to hardness when combined withcontributes to hardness when combined with palladium.palladium. www.indiandentalacademy.com
  102. 102. Need For Dental casting alloysNeed For Dental casting alloys  The Major factors areThe Major factors are  Economy – The new materials perform the sameEconomy – The new materials perform the same function as the old material but at the older costfunction as the old material but at the older cost  Performance - The new materials perform better thanPerformance - The new materials perform better than the old material in ease of processing improved handingthe old material in ease of processing improved handing characters or increased fracture resistancecharacters or increased fracture resistance  Esthetics – The new material provides more estheticEsthetics – The new material provides more esthetic results such as increased translucencyresults such as increased translucency www.indiandentalacademy.com
  103. 103. Historical Perspective On DentalHistorical Perspective On Dental Casting AlloysCasting Alloys  This history of dental casting alloys has beenThis 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
  104. 104. Historical Perspective On DentalHistorical Perspective On Dental Casting Alloys (contd)Casting Alloys (contd)  Taggarts presentation to the New York odontologicalTaggarts presentation to the New York odontological group in 1907 on the fabrication of cast inlaygroup in 1907 on the fabrication of cast inlay restorations often has been acknowledges as the firstrestorations often has been acknowledges as the first reported application of the lost wax technique inreported application of the lost wax technique in dentistry.dentistry.  The inlay technique described by Taggarat was anThe inlay technique described by Taggarat was an instant‘ success. It soon led to the casting of complexinstant‘ success. It soon led to the casting of complex inlays such as on lays, crowns, fixed partial denturesinlays such as on lays, crowns, fixed partial dentures and removable partial denture frame works.and removable partial denture frame works.  Because pure gold did not have the physicalBecause pure gold did not have the physical properties require of these dental restorations existingproperties require of these dental restorations existing jewellery alloys were quickly adopted. These gold werejewellery alloys were quickly adopted. These gold were further strengthened with Cu, Ag, or Ptfurther strengthened with Cu, Ag, or Ptwww.indiandentalacademy.com
  105. 105. Historical Perspective On DentalHistorical Perspective On Dental Casting Alloys (contd)Casting Alloys (contd)  1932, the dental materials group at the national1932, the dental materials group at the national Bureau of standards surveyed the alloys beingBureau of standards surveyed the alloys being used and roughly classified them as Type I, Typeused and roughly classified them as Type I, Type II, Type III & Type IV.II, Type III & Type IV.  At that time some tarnish tests indicated thatAt that time some tarnish tests indicated that alloys with a gold content lower than 65% toalloys with a gold content lower than 65% to 75% furnished too readily for dental use75% furnished too readily for dental use www.indiandentalacademy.com
  106. 106. Historical Perspective On DentalHistorical Perspective On Dental Casting Alloys (contd)Casting Alloys (contd)  By 1948, the composition of dental noble metalBy 1948, the composition of dental noble metal alloys for east metal restorations has becomealloys for east metal restorations has become rather diverse with these formulations, therather diverse with these formulations, the furnishing tendency of the original alloysfurnishing tendency of the original alloys apparently had disappeared.apparently had disappeared. www.indiandentalacademy.com
  107. 107. 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 rapidly thatIn 1978 the price of gold was climbing so rapidly that attention focused on the noble metal alloys to reduceattention focused on the noble metal alloys to reduce the precious metal content get retain the advantage ofthe precious metal content get retain the advantage of noble metal for dental use.noble metal for dental use. www.indiandentalacademy.com
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  109. 109. Desirable Properties Of CastingDesirable Properties Of Casting Alloys: The metals must exhibitAlloys: The metals must exhibit  1. Bio compatibility1. 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
  110. 110. 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
  111. 111. 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
  112. 112. 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 no ble metal elementsno ble metal elements Noble metalNoble metal >=25 wt% of no ble metal>=25 wt% of no ble metal Predominantly base metalPredominantly base metal <25 wt% of the noble metal<25 wt% of the noble metal elementselements www.indiandentalacademy.com
  113. 113. 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% goldcolor, with greater than 60% gold contentcontent  White golds-White golds- whitewhite color, but with more than 50%color, but with more than 50% gold contentgold content www.indiandentalacademy.com
  114. 114. 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 less thanusually yellow colored, with less than 60% gold (usually 42% to 55%)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 of goldmajor component; may contain small quantities of gold (2%) and a limited amount of either copper or cobalt(2%) and a limited amount of either copper or cobalt www.indiandentalacademy.com
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  119. 119. Metal Ceramic RestorationMetal Ceramic Restoration  By Definition – Partial crown, full crown orBy Definition – Partial crown, full crown or fixed partial denture made with a metal substratefixed partial denture made with a metal substrate to which porcelain is bonded for estheticto which porcelain is bonded for esthetic enhancement via an intermediate metal oxideenhancement via an intermediate metal oxide layerlayer  Also called as porcelain fused metal , porcelainAlso called as porcelain fused metal , porcelain bonded to metal , porcelain to metal and ceramobonded to metal , porcelain to metal and ceramo metalmetal www.indiandentalacademy.com
  120. 120. Need for metal ceramic alloysNeed for metal ceramic alloys  The chief objection for the use of dental porcelain as restorativeThe chief objection for the use of dental porcelain as restorative material is its low strength under tensile and shear, stressmaterial is its low strength under tensile and shear, stress conditionsconditions  A method by which this disadvantage can be minimized is toA method by which this disadvantage can be minimized is to bond the porcelain directly to a cast alloy sub structure made tobond the porcelain directly to a cast alloy sub structure made to fit the prepared toothfit 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 with thatPossess coefficient of thermal contraction compatible with that of dental porcelainof dental porcelain  Solidus temperature is sufficiently high to permit the aplicationSolidus temperature is sufficiently high to permit the aplication of low fusing porcelainof low fusing porcelain www.indiandentalacademy.com
  121. 121. 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 DuchateauDuchateau  1774 -1774 - byby Duchateau,was introduced inDuchateau,was introduced in England soon thereafterEngland soon thereafter byby de Chemant.de Chemant. www.indiandentalacademy.com
  122. 122. 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 in.the United States in  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
  123. 123. 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, who was the grandfatherLand, who was the grandfather ofof aviator Charlesaviator Charles Lindbergh, described a technique for fabricatingLindbergh, 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
  124. 124. 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 superb aesthetic performance and clinicallong-standing superb aesthetic performance and clinical survivability ,of metal-ceramic restara­tians.survivability ,of metal-ceramic restara­tians.  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 allays that banded chemically ta andbe used to produce allays that banded chemically ta and were thermally compatible with feldspathic porcelains.were thermally compatible with feldspathic 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
  125. 125. 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
  126. 126. 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 restorationsrestorations www.indiandentalacademy.com
  127. 127. Noble Metal ContentNoble Metal Content Indirectly denotes…..Indirectly denotes…..  Corrosion resistance of the alloysCorrosion resistance of the alloys  Inert properties of the alloysInert properties of the alloys www.indiandentalacademy.com
  128. 128. HardnessHardness  Definition - Resistance of material to plasticDefinition - Resistance of material to plastic deformationdeformation  Important in relation to occlusal wear resistanceImportant in relation to occlusal wear resistance and finishingand finishing  affects polishing propertiesaffects polishing properties www.indiandentalacademy.com
  129. 129. Yield StrengthYield Strength  The stress at which a test specimen exhibits aThe stress at which a test specimen exhibits a specific amount of plastic strainspecific amount of plastic strain  Necessary in determining Load Bearing abilityNecessary in determining Load Bearing ability especially in FPD , since cross sectional area ofespecially in FPD , since cross sectional area of metal used in PFM restoration are usuallymetal used in PFM restoration are usually smaller than that of all metal restorationssmaller than that of all metal restorations www.indiandentalacademy.com
  130. 130. ElongationElongation  Maximum amount of plastic strain a tensile testMaximum amount of plastic strain a tensile test specimen can sustain it fracturesspecimen can sustain it fractures  Related to Marginal finishing PropertiesRelated to Marginal finishing Properties especially in Partial veneer crown and abutmentsespecially in Partial veneer crown and abutments www.indiandentalacademy.com
  131. 131. Fusion TemperatureFusion Temperature  Temperature at which the metal solidifiesTemperature at which the metal solidifies  Important in relation to SAG Resistance as it isImportant in relation to SAG Resistance as it is necessary for the alloy to withstand temperaturesnecessary for the alloy to withstand temperatures of the porcelain firing cycle.of the porcelain firing cycle. www.indiandentalacademy.com
  132. 132. Chemical PropertiesChemical Properties  Tarnish ResistanceTarnish Resistance  Corrosion ResistanceCorrosion Resistance Selection of Metal Ceramic AlloysSelection of Metal Ceramic Alloys www.indiandentalacademy.com
  133. 133. Selection of Metal Ceramic AlloysSelection of Metal Ceramic Alloys thermal propertiesthermal properties  Critical for alloys used in PFM restorationsCritical for alloys used in PFM restorations  Alloys must have sufficient elevated meltingAlloys must have sufficient elevated melting Temperature range to provide dimensionalTemperature range to provide dimensional stability during porcelain firing cyclestability during porcelain firing cycle  Thermal creep results in distortions such as sagThermal creep results in distortions such as sag in FPD frame work and margin opening duringin FPD frame work and margin opening during porcelain firing cycleporcelain firing cycle www.indiandentalacademy.com
  134. 134. Selection of Metal Ceramic AlloysSelection of Metal Ceramic Alloys  Lab workability and Casting Accuracy – in orderLab workability and Casting Accuracy – in order to provide clinically acceptable castingsto provide clinically acceptable castings www.indiandentalacademy.com
  135. 135. Bio CompatibilityBio Compatibility Base metal alloys – Nickel (Ni) and BerylliumBase metal alloys – Nickel (Ni) and Beryllium (Be)(Be)  The occupational health and safetyThe occupational health and safety administration (OSHA) specifies thatadministration (OSHA) specifies that exposure to Beryllium dust in air should beexposure to Beryllium dust in air should be limited to a concentration of 2 ug /meterlimited to a concentration of 2 ug /meter cubecube www.indiandentalacademy.com
  136. 136.  The allowable maximumThe allowable maximum concentration is 5 ug /meter cubeconcentration is 5 ug /meter cube  Sensitivity – Contact dermatitisSensitivity – Contact dermatitis with Nickel or Nickel containingwith Nickel or Nickel containing alloysalloys www.indiandentalacademy.com
  137. 137. Porcelain Metal CompatibilityPorcelain Metal Compatibility  Properties to consider when choosingProperties to consider when choosing alloys for PFM restorationalloys for PFM restoration  Thermal ExpansionThermal Expansion  Bond strength of porcelain metalBond strength of porcelain metal  CompositionComposition www.indiandentalacademy.com
  138. 138. Thermal ExpansionThermal Expansion  Zero Residual Stress – desirable forZero Residual Stress – desirable for porcelain fused to metal restorationsporcelain fused to metal restorations and is achieved when total expansionand is achieved when total expansion and contraction of porcelain and metaland contraction of porcelain and metal are matched between porcelain firingare matched between porcelain firing temperature and room temperaturetemperature and room temperature www.indiandentalacademy.com
  139. 139. Bond StrengthBond Strength  Ensures retention of porcelain , bond to theEnsures retention of porcelain , bond to the surface of metal through the formation ofsurface of metal through the formation of surface oxide layer and in turn establishes thesurface oxide layer and in turn establishes the longevity of the restorationslongevity of the restorations www.indiandentalacademy.com
  140. 140. CompositionComposition  Key factor since components of alloy influencesKey factor since components of alloy influences color of porcelaincolor of porcelain  Can compromise esthetics of restorationsCan compromise esthetics of restorations  Silver-color change causes greening of porcelainSilver-color change causes greening of porcelain which occurs by exchange of silver from alloywhich occurs by exchange of silver from alloy and sodium from porcelainand sodium from porcelain www.indiandentalacademy.com
  141. 141. www.indiandentalacademy.com
  142. 142. 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 Alloys thatFore Runner of improved High Gold Alloys that remain as market today – Jelenko Oremain as market today – Jelenko O  Composed principally of Gold and PlatinumComposed principally of Gold and Platinum groupgroup www.indiandentalacademy.com
  143. 143. High gold alloysHigh gold alloys  Gold content varies from 78% -87% by weight andGold content varies from 78% -87% by weight and noble metal content is about 97%noble 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 tostrength and to promote a good porcelain bond to metal oxidemetal oxide  CostlyCostly  Light yellow in color low tensile strength makes them aLight yellow in color low tensile strength makes them a questionable choice for fixed partial denturesquestionable choice for fixed 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
  144. 144. 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 for porcelainTrace elements like indium, iron, and tin for porcelain bonding. (If the palladium content exceeds that ofbonding. (If the palladium content exceeds that of platinum, then the alloys should be classified as Au-Pd-platinum, then the alloys should be classified as Au-Pd- Pt.)Pt.) www.indiandentalacademy.com
  145. 145. 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 color NotBiocompatible Some are yellow in color Not "technique sensitive""technique sensitive"  BurnishableBurnishable www.indiandentalacademy.com
  146. 146. Gold,Platinum,Palladium AlloysGold,Platinum,Palladium Alloys (Contd)(Contd)  Disadvantages;-Disadvantages;-  High costHigh cost  Poor sag resistance so not suited for long-spanPoor sag resistance so not suited for long-span fixed partial denturesfixed partial dentures  Low hardness (greaterLow hardness (greater wear)wear)  High density (fewercastings per ounce)High density (fewercastings per ounce) www.indiandentalacademy.com
  147. 147. 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% Note :Note : Like the Au-Pt-Pd alloys, trace amounts of oxidizableLike the Au-Pt-Pd alloys, trace amounts of oxidizable elements are added for porcelain bondingelements are added for porcelain bonding.. www.indiandentalacademy.com
  148. 148. 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
  149. 149. 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
  150. 150. 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% Note :Note : Trace amounts of oxidizable elements forTrace amounts of oxidizable elements for porcelein bondingporcelein bonding www.indiandentalacademy.com
  151. 151. 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
  152. 152. 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-silver group)discoloration (but less than high-silver group) www.indiandentalacademy.com
  153. 153. 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% Note :Note : Iridium and tin are the oxidizable elements responsibleIridium and tin are the oxidizable elements responsible for porcelain bondingfor porcelain bonding www.indiandentalacademy.com
  154. 154. 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
  155. 155. Gold-Palladium alloysGold-Palladium alloys DisadvantagesDisadvantages  High costHigh cost  Not thermally compatible with high expansionNot thermally compatible with high expansion dental porcelainsdental porcelains www.indiandentalacademy.com
  156. 156. 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) Note :Note : Trace elements of other oxidizable base elements areTrace elements of other oxidizable base elements are also presentalso present www.indiandentalacademy.com
  157. 157. Palladium-Silver alloys (contd)Palladium-Silver alloys (contd) AdvantagesAdvantages  Good castability (whenGood castability (when torch casting)torch casting)  Good porcelain bondingGood porcelain bonding  Excellent sag resistance)Excellent sag 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
  158. 158. Palladium-Silver alloys (contd)Palladium-Silver alloys (contd) DisadvantagesDisadvantages  High coefficient of thermalHigh coefficient of thermal expansionexpansion  Discoloration (yellow,Discoloration (yellow, brown, or green) may occurbrown, or green) may occur with some dental porcelainswith some dental porcelains  Some castability problemsSome castability problems  Pd and Ag prone to absorbPd and Ag prone to absorb gasesgases  Require regular purgingRequire regular purging of the porcelain furnaceof the 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
  159. 159. 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% gold)(some high palladium-cobalt alloys may contain 2% gold) Note:Note: Trace amounts of oxidizable elements (such as galliumTrace amounts of oxidizable elements (such as gallium and indium) are added for porcelain bonding.and indium) are added for porcelain bonding. www.indiandentalacademy.com
  160. 160. 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 ounce (thancastings per ounce (than gold-based alloys) Some melt and cast easily Goodgold-based alloys) Some melt and cast easily Good polishabilitypolishability (supposed to be similar(supposed to be similar to Au-Pd alloys)to Au-Pd alloys)  Reportedly easier to presolder than high Pd-Cu alloysReportedly easier to presolder than high Pd-Cu alloys www.indiandentalacademy.com
  161. 161. 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-heating thanover-heating than high Pd-Cu Produce a thick, dark oxidehigh Pd-Cu Produce a thick, dark oxide Colored oxide layer may cause bluing ofColored oxide layer may cause bluing of porcelainporcelain  Prone to gas absorption Little information onProne to gas absorption Little information on long-term clinical successlong-term clinical success www.indiandentalacademy.com
  162. 162. 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) Note :Note : Trace amounts of oxidizabJe elements such asTrace amounts of oxidizabJe elements such as indium and gallium.indium and gallium. www.indiandentalacademy.com
  163. 163. 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
  164. 164. 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 prone toLike other palladium-based alloys are prone to gaseous absorptiongaseous absorption  Should not be cast in carbon cruciblesShould not be cast in carbon crucibles www.indiandentalacademy.com
  165. 165. High Palladium-Copper alloysHigh Palladium-Copper alloys CompositionComposition  Palladium: 70%-80%Palladium: 70%-80%  Copper: 9%-15%Copper: 9%-15%  Gold: 1 %-2% (if present)Gold: 1 %-2% (if present)  Platinum: 1 % (if present)Platinum: 1 % (if present) Note :Note :  Some, but not all, high palladium-copper alloys containSome, but not all, high palladium-copper alloys contain small quantities (1 %-3%) of gold and/or platinum.small quantities (1 %-3%) of gold and/or platinum.  Trace amounts of the oxidizable elements gallium,Trace amounts of the oxidizable elements gallium, indium, and tin are added for porcelain bonding.indium, and tin are added for porcelain bonding. www.indiandentalacademy.com
  166. 166. High Palladium-Copper alloysHigh Palladium-Copper alloys AdvantagesAdvantages  Good castabilityGood castability  Lower cost (thanLower cost (than gold-based alloys)gold-based alloys)  Low density means more castings per ounceLow density means more castings per ounce  Tarnish and corrosion resistantTarnish and corrosion resistant  Compatible with many dental porcelainsCompatible with many dental porcelains  Some are available inSome are available in1-dwt ingots1-dwt ingots www.indiandentalacademy.com
  167. 167. High Palladium-Copper alloysHigh Palladium-Copper alloys DisadvantagesDisadvantages  Produce dark, thick oxides May discolor (gray)Produce dark, thick oxides May discolor (gray) some dental porcelainssome dental porcelains  Must visually evaluate oxide color to determineMust visually evaluate oxide color to determine if proper adherent oxide was formedif proper adherent oxide was formed  Should not be cast in carbon crucibles (electricShould not be cast in carbon crucibles (electric casting machines)casting machines)  Prone to gaseousProne to gaseous absorptionabsorption www.indiandentalacademy.com
  168. 168. High Palladium-Copper alloysHigh Palladium-Copper alloys Disadvantages (Contd)Disadvantages (Contd)  Subject to thermal creep (marginal opening)Subject to thermal creep (marginal opening)  May not be suitable for long-span fixed partialMay not be suitable for long-span fixed partial denturesdentures  Little information onLittle information on long-term clinicallong-term clinical successsuccess  May be difficult to polishMay be difficult to polish  Presoldering may be a problemPresoldering may be a problem  High hardnessHigh hardness www.indiandentalacademy.com
  169. 169. Nickel-chromium-beryllium alloysNickel-chromium-beryllium alloys CompositionComposition  Nickel: 62%-82%Nickel: 62%-82%  Chromium: 11 %-20%Chromium: 11 %-20%  Beryllium: up to 2.0%Beryllium: up to 2.0% Numerous minor alloying elements include, butNumerous minor alloying elements include, but are not limited to: aluminum, carbon, gallium,are not limited to: aluminum, carbon, gallium, iron, manganese, molybdenum, silicon, titanium,iron, manganese, molybdenum, silicon, titanium, and/or vanadiumand/or vanadium www.indiandentalacademy.com
  170. 170. Nickel-chromium-beryllium alloysNickel-chromium-beryllium alloys AdvantagesAdvantages  Low costLow cost  Low density permits more casting per ounceLow density permits more casting per ounce  High sag resistanceHigh sag resistance  Can produce thin castingsCan produce thin castings  Poor thermal conductorPoor thermal conductor  Can be etchedCan be etched www.indiandentalacademy.com
  171. 171. Nickel-chromium-beryllium alloysNickel-chromium-beryllium alloys DisadvantagesDisadvantages  Cannot use with nickel­ sensitive patientsCannot use with nickel­ sensitive patients  Beryllium exposure may be potentially harmful toBeryllium exposure may be potentially harmful to technicians and patientstechnicians and patients  Proper melting and casting is a learned skillProper melting and casting is a learned skill  Bond failure more common in the oxide layerBond failure more common in the oxide layer  High hardness (may wear opposing teeth) Difficult toHigh hardness (may wear opposing teeth) Difficult to soldersolder  Ingots do not poolIngots do not pool  Difficult to cut through cemented castingsDifficult to cut through cemented castings www.indiandentalacademy.com
  172. 172. Nickel-chromium beryllium-freeNickel-chromium beryllium-free alloysalloys CompositionComposition  Nickel: 62%-77%Nickel: 62%-77%  Chromium: 11 %-22%Chromium: 11 %-22% Boron (some), iron, molybdenum, niobium (orBoron (some), iron, molybdenum, niobium (or colurr)ium), and/or tantalum.colurr)ium), and/or tantalum. www.indiandentalacademy.com
  173. 173. Nickel-chromium beryllium-freeNickel-chromium beryllium-free alloysalloys AdvantagesAdvantages  Do not contain berylliumDo not contain beryllium  Low costLow cost  Low density means more castings per ounceLow density means more castings per ounce www.indiandentalacademy.com
  174. 174. Nickel-chromium beryllium-freeNickel-chromium beryllium-free alloysalloys DisadvantagesDisadvantages  Cannot use with nickel-sensitive patients CannotCannot use with nickel-sensitive patients Cannot be etchedbe etched  May not cast as well asMay not cast as well as Ni-Cr-Be alloysNi-Cr-Be alloys  Produce more oxides thanProduce more oxides than Ni-Cr-Be alloysNi-Cr-Be alloys www.indiandentalacademy.com
  175. 175. Cobalt-chromium alloysCobalt-chromium alloys CompositionComposition  Cobalt: 53%-68%Cobalt: 53%-68%  Chromium: 25%-34% / Trace elements includeChromium: 25%-34% / Trace elements include molybdenum, ruthenium /(some) and/ormolybdenum, ruthenium /(some) and/or wolfram.wolfram. www.indiandentalacademy.com
  176. 176. Cobalt-chromium alloysCobalt-chromium alloys AdvantagesAdvantages  Do not contain nickelDo not contain nickel  Do not contain berylliumDo not contain beryllium  Poor thermal conductorsPoor thermal conductors  Low densityLow density  Low costLow cost www.indiandentalacademy.com
  177. 177. Cobalt-chromium alloysCobalt-chromium alloys DisadvantagesDisadvantages  More difficult to process than nickel-base alloysMore difficult to process than nickel-base alloys  High hardness (may wear the opposingHigh hardness (may wear the opposing dentition)dentition)  Oxidize more than bothOxidize more than both nickel-based alloysnickel-based alloys  No information onNo information on long-term clinical studieslong-term clinical studies www.indiandentalacademy.com
  178. 178. Titanium alloysTitanium alloys  High biocompatibilityHigh biocompatibility  According to the American Society for Testing andAccording to the American Society for Testing and Materials (ASTM), there are five unalloyed grades of CPMaterials (ASTM), there are five unalloyed grades of CP Ti (Grades 1-4, and Grade 7), based on the concentra­Ti (Grades 1-4, and Grade 7), based on the concentra­ tion oftion of  oxygen (0.18 wt% to 0.40 wt%) andoxygen (0.18 wt% to 0.40 wt%) and  iron (0.2 wt% to 0.5 wt%).iron (0.2 wt% to 0.5 wt%).  Other impu­rities include nitrogen (0.03 wt% to 0.05 wtOther impu­rities include nitrogen (0.03 wt% to 0.05 wt %),%),  carbon (0.1 m%), and hydrogen (0.015 wt%).carbon (0.1 m%), and hydrogen (0.015 wt%). www.indiandentalacademy.com
  179. 179. Titanium alloysTitanium alloys  Grade 1 CP Ti is the purest and softest form.Grade 1 CP Ti is the purest and softest form.  It has a moderately high tensile strengthIt has a moderately high tensile strength  moderately high stiffness,moderately high stiffness,  low density,low density,  low ther­mal expansion coefficient.low ther­mal expansion coefficient.  The elastic modulus of CP Ti is compa­rable toThe elastic modulus of CP Ti is compa­rable to that of tooth enamel and noble alloys, but it isthat of tooth enamel and noble alloys, but it is lower than that of other baselower than that of other base www.indiandentalacademy.com
  180. 180. Titanium alloysTitanium alloys  Casting of titanium alloys is difficult due to aCasting of titanium alloys is difficult due to a high casting temperature – 2000 chigh casting temperature – 2000 c  Rapid oxidation and reactions with investmentsRapid oxidation and reactions with investments  Melting is done in specially designed furnacesMelting is done in specially designed furnaces with an argon atmospherewith an argon atmosphere  Ti-6Al-4v has been used for PFM restorationsTi-6Al-4v has been used for PFM restorations  Used with low expansions porcelainsUsed with low expansions porcelains www.indiandentalacademy.com
  181. 181. Noble Metal AlloysNoble Metal Alloys AuAu PdPd PtPt AgAg SnSn InIn Gold Platinum PalladiumGold Platinum Palladium SMG-2 (J.M.Ney Co)SMG-2 (J.M.Ney Co) 8787 55 77 -- <1<1 <1<1 Ultra Gold (J.F. Jelenko & Co)Ultra Gold (J.F. Jelenko & Co) 87.587.5 11 1010 -- ++ ++ Degudent H (Degussa Corp)Degudent H (Degussa Corp) 84.584.5 55 88 -- -- 2.52.5 Rx Y-Ceramic (Jeneric / Pentron,Rx Y-Ceramic (Jeneric / Pentron, Inc)Inc) 8484 66 77 11 0.70.7 0.50.5 700SL (Leach & Dillion)700SL (Leach & Dillion) 8484 66 77 1.51.5 -- 11 Will-Ceram Y2 (Williams DentalWill-Ceram Y2 (Williams Dental Co)Co) 8282 4.54.5 88 3.53.5 <1<1 <1<1 www.indiandentalacademy.com
  182. 182. AuAu PdPd PtPt AgAg SnSn InIn Gold Platinum PalladiumGold Platinum Palladium Jelenko O (J.F. Jelenko & Co)Jelenko O (J.F. Jelenko & Co) 87.587.5 66 4.54.5 11 0.40.4 0.30.3 Image (J.M. Ney Co)Image (J.M. Ney Co) 8585 55 55 44 <1<1 -- Gold PlatinumGold Platinum RhRh Rx-G (Jeneric / Pentron,Inc)Rx-G (Jeneric / Pentron,Inc) 8787 -- 1010 -- ++ ++ 1.51.5 Degudent G (Degussa Corp)Degudent G (Degussa Corp) 8686 -- 10.510.5 -- ++ <2<2 -- www.indiandentalacademy.com
  183. 183. AuAu PdPd PtPt AgAg SnSn InIn Gold Platinum SilverGold Platinum Silver Will Ceram WWill Ceram W (Williams Dental Co)(Williams Dental Co) 5454 26.526.5 -- 15.515.5 <5<5 <5<5 Cameo (J.F. Jelenko & Co)Cameo (J.F. Jelenko & Co) 52.552.5 2727 -- 1616 22 2.52.5 Rx WCG (Jeneric/Pentron,Inc)Rx WCG (Jeneric/Pentron,Inc) 5252 2828 -- 1414 11 33 Special White (Degussa Corp)Special White (Degussa Corp) 4545 4040 -- 16.516.5 33 44 www.indiandentalacademy.com
  184. 184. www.indiandentalacademy.com
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  193. 193. Sub structure designSub structure design  majority of the porcelain-to-metal bond failuresmajority of the porcelain-to-metal bond failures occur as a direct result of improper substructureoccur as a direct result of improper substructure designdesign  Errors in the preparation of the metal ceramicErrors in the preparation of the metal ceramic sub­structure frequently go unnoticed until thesub­structure frequently go unnoticed until the brittle porcelain veneer fails in service.brittle porcelain veneer fails in service. www.indiandentalacademy.com
  194. 194. Sub structure design (contd)Sub structure design (contd)  Hence necessary to understand the essentials ofHence necessary to understand the essentials of proper substructure de­sign, since it will help toproper substructure de­sign, since it will help to ensure the longevity of the final prosthesis.ensure the longevity of the final prosthesis. www.indiandentalacademy.com
  195. 195. Primary functionPrimary function  1. The casting provides the fit of the restoration1. The casting provides the fit of the restoration to the prepared toothto the prepared tooth  2. The metal forms oxides that bond chemically2. The metal forms oxides that bond chemically toto dental porcelain.dental porcelain.  3. The coping serves as a rigid foundation to3. The coping serves as a rigid foundation to which the brittle porcelain can be attached forwhich the brittle porcelain can be attached for increased strength and support.increased strength and support.  4. The substructure restores the tooth's proper4. The substructure restores the tooth's proper emergence profile.emergence profile. www.indiandentalacademy.com
  196. 196. Fit of the restorationFit of the restoration  Fit should be evaluated in terms of bothFit should be evaluated in terms of both seatseat (incisal or occlusal(incisal or occlusal gap) andgap) and sealseal (marginal opening).(marginal opening).  A restoration that binds against tooth structure is apt to stressA restoration that binds against tooth structure is apt to stress the porcelain-metal bond and most likely will not seat or sealthe porcelain-metal bond and most likely will not seat or seal completely.completely.  Conversely, an over expanded metal substructure invariably willConversely, an over expanded metal substructure invariably will rely more heavily on the cement luting agent for its retentionrely more heavily on the cement luting agent for its retention than on good internal adaptation, and the latter resto­ration isthan on good internal adaptation, and the latter resto­ration is doomed to failure.doomed to failure.  A properly formed metal ceramic substructure should have whatA properly formed metal ceramic substructure should have what is called ais called a passivepassive fit and provide both internal adaptation (seat)fit and provide both internal adaptation (seat) and marginal integrity (seal).and marginal integrity (seal). www.indiandentalacademy.com
  197. 197. OxidationOxidation  A properly oxidized substrate can enhance theA properly oxidized substrate can enhance the attachment between porcelain and metalattachment between porcelain and metal  poorly contoured coping may permit stresspoorly contoured coping may permit stress concentrations to form as the fired porcelain cools toconcentrations to form as the fired porcelain cools to room temperature.room temperature.  In turn, these stresses in the porcelain may notIn turn, these stresses in the porcelain may not manifest themselves initially, but they can appear latermanifest themselves initially, but they can appear later and possibly lead to a bond failureand possibly lead to a bond failure www.indiandentalacademy.com

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