metals and alloys for prosthodontics / academy of fixed orthodontics

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metals and alloys for prosthodontics / academy of fixed orthodontics

  1. 1. INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY Leader in continuing dental educationLeader in continuing dental education www.indiandentalacademy.comwww.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com
  2. 2. www.indiandentalacademy.comwww.indiandentalacademy.com
  3. 3. Materials Science & Engineering Dept. Research Experience for Undergraduates
  4. 4. INTRODUCTION DEFINITION METALLURGY -TYPES GENERAL CHARACTERISTICS OF METALS STRUCTURE AND PROPERTIES OF METALS CONTENTS www.indiandentalacademy.com
  5. 5.  CRYSTALLINE STRUCTURE  NUCLEI  DENDRITES  GRAIN  GRAIN BOUNDARIES  EQUIAXED GRAIN STRUCTURE  LATTICE TYPES  DISLOCATIONS  SLIP PLANES www.indiandentalacademy.com
  6. 6.  QUENCHING  REFINED GRAIN STRUCTURE  SEEDING COLD WORKING  DUCTILITY  MALLEABILITY  COLD WORKING  FIBROUS STRUCTURE  WORK HARDENING  RECRYSTALLIZATION TEMPERATURE  GRAIN GROWTH ANNEALING  STRESS RELIEF ANNEALINGwww.indiandentalacademy.com
  7. 7. STRUCTURE AND PROPERTIES OF ALLOYS ALLOY ALLOY SYSTEM METALLOID AMALGAM BINARY TERNARY QUATERNARY www.indiandentalacademy.com
  8. 8. SOLID SOLUTION – PHASE  SUBSTITUTIONAL SOLID SOLUTION  INTERSTITIAL SOLID SOLUTION  SOLUTION HARDENING  (COOLING CURVE) TIME-TEMPERATURE CURVE  CORED STRUCTURE  CORING  PHASE DIAGRAM  LIQUIDUS LINE  SOLIDUS LINE  HOMOGENISATION INTERMETALLIC COMPOUND EUTECTIC FORMATION PERITECTIC ALLOYS www.indiandentalacademy.com
  9. 9. CLASSIFICATION OF METALS AND ALLOY SYSTEMS DENTAL CASTING ALLOYS - DESIRABLE PROPERTIES AND USES www.indiandentalacademy.com
  10. 10.  NICKEL-CHROMIUM ALLOYS  COBALT-CHROMIUM ALOYS (STELLITES) TITANIUM AND TITANIUM ALLOYS ALLOYS FOR METAL CERAMIC RESTORATIONS PARTIAL DENTURE ALLOYS www.indiandentalacademy.com
  11. 11.  WROUGHT ALLOYS AND GOLD ALLOYS CARBON STEELS STAINLESS STEEL COBALT-CHROMIUM (ELGILOY) NICKEL ALLOYS NICKEL-TITANIUM ALLOYS (NITINOL) β-TITANIUM ALLOYS GOLD ALLOYS SILVER-PALLADIUM ALLOYS DENTAL IMPLANT MATERIALS www.indiandentalacademy.com
  12. 12. BIOCOMPATIBILITY CONCLUSION REFERENCES www.indiandentalacademy.com
  13. 13. www.indiandentalacademy.comwww.indiandentalacademy.com
  14. 14. www.indiandentalacademy.comwww.indiandentalacademy.com
  15. 15. GPT 8 (GPT 8 (20052005) defines “) defines “METALMETAL” as any” as any strongstrong relativelyrelatively ductileductile substance thatsubstance that providesprovides electropositive ionselectropositive ions to ato a corrosive environment and that can becorrosive environment and that can be polished to a highpolished to a high lustrelustre. Characterized. Characterized byby metallic atomic bondingmetallic atomic bonding.. www.indiandentalacademy.comwww.indiandentalacademy.com
  16. 16. The metals handbookThe metals handbook ((19921992) defines a “metal as) defines a “metal as an opaque lustrous chemical substance that is aan opaque lustrous chemical substance that is a goodgood conductor of heatconductor of heat and electricity and,and electricity and, whenwhen polishedpolished, is a, is a good reflector of lightgood reflector of light”” www.indiandentalacademy.comwww.indiandentalacademy.com
  17. 17. In dentistry,In dentistry, metalsmetals representrepresent one of the fourone of the four major classes of materials used for themajor classes of materials used for the reconstruction of decayed, damaged orreconstruction of decayed, damaged or missing teeth.missing teeth. www.indiandentalacademy.comwww.indiandentalacademy.com
  18. 18. The science and art of theThe science and art of the extractionextraction of metalsof metals from theirfrom their oresores together with the refinement oftogether with the refinement of thesethese metalsmetals and their adaption to variousand their adaption to various usesuses.. METALLURGYMETALLURGY www.indiandentalacademy.comwww.indiandentalacademy.com
  19. 19. TheThe extensive useextensive use of metals and theirof metals and their combination during recent years has madecombination during recent years has made specializationspecialization in this field. This specializationin this field. This specialization has resulted in the development ofhas resulted in the development of severalseveral branchesbranches of metallurgy , some of which areof metallurgy , some of which are closely associated withclosely associated with chemistry, physicschemistry, physics andand mechanics.mechanics. www.indiandentalacademy.comwww.indiandentalacademy.com
  20. 20. Understanding of metallurgy and theUnderstanding of metallurgy and the characteristiccharacteristic behaviorbehavior of various metals, orof various metals, or combination of metals to formcombination of metals to form alloysalloys, is, is highlyhighly desirabledesirable in the study ofin the study of restorativerestorative materialsmaterials for several reasons like :for several reasons like : There areThere are numerous metalsnumerous metals which are used inwhich are used in various restorative operations.various restorative operations. www.indiandentalacademy.comwww.indiandentalacademy.com
  21. 21. A knowledge of the characteristic behaviorA knowledge of the characteristic behavior of metals is essential for anof metals is essential for an understanding ofunderstanding of the qualitythe quality of the restoration fabricated fromof the restoration fabricated from metals.metals. The properties that the metal or alloy willThe properties that the metal or alloy will display are quiet reproducible and serve asdisplay are quiet reproducible and serve as guide in the studyguide in the study of the many related issuesof the many related issues to the fabrication of dental restorations.to the fabrication of dental restorations. www.indiandentalacademy.comwww.indiandentalacademy.com
  22. 22. METALLURGYMETALLURGY  CHEMICALCHEMICAL  PHYSICALPHYSICAL  MECHANICALMECHANICAL www.indiandentalacademy.comwww.indiandentalacademy.com
  23. 23. Chemical metallurgy deals principally withChemical metallurgy deals principally with the production andthe production and refinementrefinement of metals.of metals. Sometimes it is described as “Sometimes it is described as “processprocess”” metallurgy since it considers themetallurgy since it considers the processingprocessing of oresof ores for thefor the productionproduction of metals.of metals. CHEMICAL METALLURGYCHEMICAL METALLURGY www.indiandentalacademy.comwww.indiandentalacademy.com
  24. 24. PHYSICAL METALLURGYPHYSICAL METALLURGY Physical metallurgy isPhysical metallurgy is newer sciencenewer science andand deals with thedeals with the structurestructure of possibleof possible alteration in structure as well as thealteration in structure as well as the characteristic physical propertiescharacteristic physical properties of metals.of metals. In some respects physical metallurgy andIn some respects physical metallurgy and metallographymetallography are closely related.are closely related. www.indiandentalacademy.comwww.indiandentalacademy.com
  25. 25. MetallographyMetallography is primarily theis primarily the microscopicmicroscopic examination of theexamination of the internal structureinternal structure ofof metals. This metallographic examinationmetals. This metallographic examination gives somegives some indicationindication of theof the physicalphysical behaviorbehavior which the metal can be expected towhich the metal can be expected to exhibit.exhibit. www.indiandentalacademy.comwww.indiandentalacademy.com
  26. 26. MECHANICAL METALLURGYMECHANICAL METALLURGY It includes various processes in theIt includes various processes in the fabricationfabrication of a structureof a structure such as thesuch as the castingcasting,, rollingrolling oror drawingdrawing operations.operations. InIn restorative materialsrestorative materials,, physical metallurgyphysical metallurgy combined withcombined with metallographymetallography and theand the mechanicalmechanical phase of metallurgy are ofphase of metallurgy are of greatestgreatest importance.importance. www.indiandentalacademy.comwww.indiandentalacademy.com
  27. 27. FERROUS METALLURGYFERROUS METALLURGY It is the metallurgy ofIt is the metallurgy of ironiron andand steelsteel.. InIn dentistrydentistry it is important in connection withit is important in connection with the manufacture and use ofthe manufacture and use of steel instrumentssteel instruments andand equipmentsequipments as well asas well as stainless steelstainless steel appliancesappliances.. FURTHER SUBDIVISIONS www.indiandentalacademy.comwww.indiandentalacademy.com
  28. 28. NON-FERROUS METALLURGYNON-FERROUS METALLURGY It is the metallurgy ofIt is the metallurgy of all metalall metal andand alloysalloys other thanother than iron and steeliron and steel .. E.g.E.g. : Gold alloys, platinum alloys,: Gold alloys, platinum alloys, Cr - CoCr - Co oror stellite alloysstellite alloys, as well as bronze, aluminum,, as well as bronze, aluminum, and low fusing alloys etc.,and low fusing alloys etc., www.indiandentalacademy.comwww.indiandentalacademy.com
  29. 29. General characteristics of metalsGeneral characteristics of metals A metal is any element thatA metal is any element that ionizes positivelyionizes positively inin solution.solution. Metals have certainMetals have certain typicaltypical andand characteristiccharacteristic propertiesproperties that tend to identify and distinguishthat tend to identify and distinguish them from the nonmetallic elements, such asthem from the nonmetallic elements, such as lustrelustre,, opacityopacity,, densitydensity,, thermalthermal andand electricalelectrical conductivityconductivity.. www.indiandentalacademy.comwww.indiandentalacademy.com
  30. 30. ExtremeExtreme ductilityductility andand malleabilitymalleability are oftenare often desirable in metals used in dentistry anddesirable in metals used in dentistry and these are found tothese are found to predominatepredominate inin purepure metalsmetals rather than in alloys.rather than in alloys. www.indiandentalacademy.comwww.indiandentalacademy.com
  31. 31. STRUCTURE AND PROPERTIES OF METALS Metals usually have crystalline structures in the solid state. www.indiandentalacademy.comwww.indiandentalacademy.com
  32. 32. In 1665,In 1665, Robert HookeRobert Hooke ((1635 - 17031635 - 1703) simulated) simulated the characteristic shapes of crystals by stackingthe characteristic shapes of crystals by stacking musket balls in piles.musket balls in piles. AA SPACE LATTICESPACE LATTICE can be defined ascan be defined as any arrangement of atoms in space such thatany arrangement of atoms in space such that every atom isevery atom is situated similarlysituated similarly to every otherto every other atom. It is also called aatom. It is also called a crystalcrystal.. www.indiandentalacademy.comwww.indiandentalacademy.com
  33. 33. There areThere are 1414 possible lattice types or forms, butpossible lattice types or forms, but many of the metals used in dentistry belong to themany of the metals used in dentistry belong to the cubic systemcubic system arrangement.arrangement.  Simple cubic space latticeSimple cubic space lattice  Single cells of cubic space latticeSingle cells of cubic space lattice  Simple cubicSimple cubic  Face-centered cubicFace-centered cubic  Body-centered cubicBody-centered cubic  ModelsModels www.indiandentalacademy.comwww.indiandentalacademy.com
  34. 34. www.indiandentalacademy.comwww.indiandentalacademy.com
  35. 35. Other simple lattice types of dental interest.Other simple lattice types of dental interest. A) RhombohedralA) Rhombohedral b) Orthorhombicb) Orthorhombic c) Monoclinicc) Monoclinic d) Triclinic e) Tetragonald) Triclinic e) Tetragonal f) Simple hexagonalf) Simple hexagonal g) Close packed hexagonal h) rhombic.g) Close packed hexagonal h) rhombic. www.indiandentalacademy.comwww.indiandentalacademy.com
  36. 36. www.indiandentalacademy.comwww.indiandentalacademy.com
  37. 37. When a molten metal or alloy is cooled, the solidification process is one of crystallization and is initiated at specific sites called nucleinuclei. The nuclei are formed from impurities within the molten mass of metal. www.indiandentalacademy.comwww.indiandentalacademy.com
  38. 38. www.indiandentalacademy.comwww.indiandentalacademy.com
  39. 39. Crystals grow as dendrites, which can be described as three-dimensional, branched network structures emanating from the central nucleus www.indiandentalacademy.comwww.indiandentalacademy.com
  40. 40. Crystal growth continue until all the material has solidified and all the dendritic crystals are in contact. www.indiandentalacademy.comwww.indiandentalacademy.com
  41. 41. Each crystal is known as a graingrain and the area between two grains in contact is the graingrain boundaryboundary www.indiandentalacademy.comwww.indiandentalacademy.com
  42. 42. After crystallization, the grains, haveAfter crystallization, the grains, have approximately theapproximately the same dimensionssame dimensions inin eacheach direction, measureddirection, measured from thefrom the central nucleuscentral nucleus.. They areThey are notnot perfectly spherical or cubicperfectly spherical or cubic however,however, nornor do theydo they conformconform to any otherto any other geometric shapegeometric shape. They are said to have an. They are said to have an equiaxed grain structure.. www.indiandentalacademy.comwww.indiandentalacademy.com
  43. 43. A change from anA change from an equiaxed structureequiaxed structure to one into one in which the grains have a more elongated,which the grains have a more elongated, fibrousfibrous structurestructure can cause importantcan cause important changes inchanges in mechanical properties.mechanical properties. www.indiandentalacademy.comwww.indiandentalacademy.com
  44. 44. The arrangement adopted by any oneThe arrangement adopted by any one crystal depends on specific factors such ascrystal depends on specific factors such as atomic radiusatomic radius andand charge distributionscharge distributions onon the atoms. Although there is a tendencythe atoms. Although there is a tendency towards a perfect crystal structure,towards a perfect crystal structure, occasionaloccasional defectsdefects occur.occur. www.indiandentalacademy.comwww.indiandentalacademy.com
  45. 45. www.indiandentalacademy.comwww.indiandentalacademy.com
  46. 46. Such defects are normally referred to asSuch defects are normally referred to as dislocationsdislocations and their occurrence has anand their occurrence has an effect on theeffect on the ductilityductility of the metal or alloy.of the metal or alloy. www.indiandentalacademy.comwww.indiandentalacademy.com
  47. 47. When the material is placed under a sufficientlyWhen the material is placed under a sufficiently high stress the dislocation is able to movehigh stress the dislocation is able to move through the lattice until it reaches a grainthrough the lattice until it reaches a grain boundary. Theboundary. The planeplane along which the dislocationalong which the dislocation moves is called amoves is called a slip plane and the stressand the stress required to initiate movement is therequired to initiate movement is the elastic limitelastic limit.. www.indiandentalacademy.comwww.indiandentalacademy.com
  48. 48. www.indiandentalacademy.comwww.indiandentalacademy.com
  49. 49. Grain boundariesGrain boundaries form aform a natural barriernatural barrier to theto the movement ofmovement of dislocationsdislocations. The concentration of. The concentration of grain boundaries increases as the grain sizegrain boundaries increases as the grain size decreases.decreases. Metals with finer grain structure areMetals with finer grain structure are generally harder and have higher values ofgenerally harder and have higher values of elastic limit than those with coarser grainelastic limit than those with coarser grain structure.structure. Hence it can be seen that materialHence it can be seen that material properties can be controlled to some extent byproperties can be controlled to some extent by controlling the grain sizecontrolling the grain size.. www.indiandentalacademy.comwww.indiandentalacademy.com
  50. 50. AA fine grain structurefine grain structure can be achieved bycan be achieved by rapidrapid cooling of the molten metalcooling of the molten metal or alloy followingor alloy following casting. This process, often referred to ascasting. This process, often referred to as quenchingquenching, ensures that many nuclei of, ensures that many nuclei of crystallization are formed, resulting in acrystallization are formed, resulting in a largelarge numbernumber ofof relatively small grainsrelatively small grains.. www.indiandentalacademy.comwww.indiandentalacademy.com
  51. 51. www.indiandentalacademy.comwww.indiandentalacademy.com
  52. 52. Slow coolingSlow cooling causes relativelycauses relatively few nucleifew nuclei to beto be formed which results in aformed which results in a larger grain sizelarger grain size.. Some metals and alloys are said to have aSome metals and alloys are said to have a refinedrefined grain structure.grain structure. This is normally a fine grainThis is normally a fine grain structure which is achieved bystructure which is achieved by seedingseeding thethe molten metal with anmolten metal with an additive metaladditive metal which formswhich forms nuclei crystallizationnuclei crystallization.. www.indiandentalacademy.comwww.indiandentalacademy.com
  53. 53. For an appliedFor an applied tensile forcetensile force thethe maximum degreemaximum degree of extensionof extension is a measure theis a measure the ductilityductility of theof the metal or alloy.metal or alloy. For an appliedFor an applied compressive forcecompressive force thethe maximummaximum degree of compressiondegree of compression is a measure ofis a measure of malleabilitymalleability.. These changes occur when the stress is greaterThese changes occur when the stress is greater than the elastic limit and atthan the elastic limit and at relatively lowrelatively low temperaturestemperatures.. COLD WORKINGCOLD WORKING www.indiandentalacademy.comwww.indiandentalacademy.com
  54. 54. Such cold working not only produces aSuch cold working not only produces a changechange in microstructurein microstructure, with dislocations becoming, with dislocations becoming concentrated at grain boundaries, but also aconcentrated at grain boundaries, but also a change in grain shapechange in grain shape.. The grains areThe grains are no longer equiaxedno longer equiaxed but take up abut take up a moremore fibrousfibrous.. www.indiandentalacademy.comwww.indiandentalacademy.com
  55. 55. www.indiandentalacademy.comwww.indiandentalacademy.com
  56. 56. Cold workingCold working is sometimes referred to asis sometimes referred to as workwork hardeninghardening due to the effect on mechanicaldue to the effect on mechanical properties. When mechanical work is carried outproperties. When mechanical work is carried out on a metal or alloy at a moreon a metal or alloy at a more elevatedelevated temperaturetemperature it is possible for the object to changeit is possible for the object to change shapeshape withoutwithout any alteration in grain shape orany alteration in grain shape or mechanical properties.mechanical properties. www.indiandentalacademy.comwww.indiandentalacademy.com
  57. 57. The temperatureThe temperature belowbelow whichwhich work hardening iswork hardening is possiblepossible is termed theis termed the recrystallizationrecrystallization temperature.temperature. If the material is maintained above theIf the material is maintained above the recrystallization temperature for sufficient time,recrystallization temperature for sufficient time, diffusion of atomsdiffusion of atoms across grain boundaries mayacross grain boundaries may occur, leading tooccur, leading to grain growthgrain growth..  It is clear that grain growth should beIt is clear that grain growth should be avoidedavoided ifif the properties arethe properties are not to be adverselynot to be adversely affected.affected. www.indiandentalacademy.comwww.indiandentalacademy.com
  58. 58. It is process ofIt is process of heatingheating a metal toa metal to reverse thereverse the effectseffects associated with cold working such asassociated with cold working such as strainstrain hardening, low ductilityhardening, low ductility andand distorted grains.distorted grains. In general it hasIn general it has 33 stages.stages. 1)1) RRecoveryecovery 2)2) RRecrystallizationecrystallization 3)3) GGrain growth.rain growth. AnnealingAnnealing www.indiandentalacademy.comwww.indiandentalacademy.com
  59. 59.  RecoveryRecovery : is considered the stage at: is considered the stage at which thewhich the coldwork properties begin tocoldwork properties begin to disappeardisappear before any significant visiblebefore any significant visible changes are observed under thechanges are observed under the microscope.microscope. www.indiandentalacademy.comwww.indiandentalacademy.com
  60. 60.  RecrystallizationRecrystallization :: when a severely cold worked metal iswhen a severely cold worked metal is annealed, recrystallization occurs after theannealed, recrystallization occurs after the recovery stage. Therecovery stage. The old grains disappearold grains disappear completely and arecompletely and are placed by a new set ofplaced by a new set of strain free grainsstrain free grains.. www.indiandentalacademy.comwww.indiandentalacademy.com
  61. 61.  Grain growthGrain growth:: The crystallized structure has a certainThe crystallized structure has a certain average grain sizeaverage grain size, depending on the, depending on the number of nuclei .Thenumber of nuclei .The more severemore severe thethe cold working, thecold working, the greater the numbergreater the number ofof such nuclei. Thus, the grain size forsuch nuclei. Thus, the grain size for completely recrystallized material cancompletely recrystallized material can range from ratherrange from rather finefine toto fairly coarsefairly coarse.. www.indiandentalacademy.comwww.indiandentalacademy.com
  62. 62.  Cold working may cause the formation ofCold working may cause the formation of internal stressesinternal stresses within a metal object. If thesewithin a metal object. If these stresses are gradually relieved they may causestresses are gradually relieved they may cause distortiondistortion which could lead towhich could lead to loss of fitloss of fit of, forof, for exampleexample, an orthodontic appliance., an orthodontic appliance.  For certain metals and alloys theFor certain metals and alloys the internal stressesinternal stresses can becan be whollywholly oror partly eliminatedpartly eliminated by using aby using a low temperature heat treatmentlow temperature heat treatment referred to asreferred to as stress relief annealingstress relief annealing.. www.indiandentalacademy.comwww.indiandentalacademy.com
  63. 63.  This heat treatment is carried out wellThis heat treatment is carried out well belowbelow thethe recrystallization temperaturerecrystallization temperature and hasand has nono deleterious effectdeleterious effect onon mechanical propertiesmechanical properties sincesince the original grain structure is maintained.the original grain structure is maintained. www.indiandentalacademy.comwww.indiandentalacademy.com
  64. 64. STRUCTURE AND PROPERTIES OFSTRUCTURE AND PROPERTIES OF ALLOYSALLOYS  AnAn alloyalloy is a mixture ofis a mixture of two or more metalstwo or more metals.. Mixtures ofMixtures of twotwo metals are termedmetals are termed Binary alloysBinary alloys,, mixtures ofmixtures of three metalsthree metals areare Ternary alloysTernary alloys similarly mixture ofsimilarly mixture of four metalsfour metals is termed asis termed as Quaternary alloysQuaternary alloys etc.etc.  The termThe term alloy systemalloy system refers to all possiblerefers to all possible compositions of an alloy. Forcompositions of an alloy. For exampleexample thethe silver-silver- copper systemcopper system refers to all alloys withrefers to all alloys with compositions ranging betweencompositions ranging between 100% silver100% silver andand 100% copper100% copper.. www.indiandentalacademy.comwww.indiandentalacademy.com
  65. 65.  In the molten state metals usually showIn the molten state metals usually show mutual solubilitymutual solubility, one within another., one within another. When the molten mixture isWhen the molten mixture is cooledcooled toto below the melting pointbelow the melting point the followingthe following things can occur.things can occur.  The component metals mayThe component metals may remainremain soluble in each othersoluble in each other forming aforming a solidsolid solutionsolution.. www.indiandentalacademy.comwww.indiandentalacademy.com
  66. 66.  The solid solution may take one ofThe solid solution may take one of threethree formsforms. It may be a. It may be a random solid solutionrandom solid solution in which the component metal atomsin which the component metal atoms occupyoccupy random sitesrandom sites in a common crystalin a common crystal lattice.lattice. www.indiandentalacademy.comwww.indiandentalacademy.com
  67. 67. www.indiandentalacademy.comwww.indiandentalacademy.com
  68. 68. Another possibility is the formation of anAnother possibility is the formation of an ordered solid solutionordered solid solution in which component metalin which component metal atoms occupyatoms occupy specific sitesspecific sites within a commonwithin a common crystal lattice.crystal lattice. www.indiandentalacademy.comwww.indiandentalacademy.com
  69. 69. The third type of solid solution is theThe third type of solid solution is the interstitialinterstitial solid solutionsolid solution in which, for binary alloys, thein which, for binary alloys, the primary lattice sites are occupied by one metalprimary lattice sites are occupied by one metal atomatom and theand the atoms of the second component doatoms of the second component do not occupy lattice sites but lie within thenot occupy lattice sites but lie within the interstices of the latticeinterstices of the lattice. This is normally found. This is normally found where thewhere the atomic radiusatomic radius of one component isof one component is muchmuch smallersmaller than that of the other.than that of the other. www.indiandentalacademy.comwww.indiandentalacademy.com
  70. 70. www.indiandentalacademy.comwww.indiandentalacademy.com
  71. 71. www.indiandentalacademy.comwww.indiandentalacademy.com
  72. 72. Solid solutions are generallySolid solutions are generally harder, strongerharder, stronger andand havehave higher valueshigher values of elastic limit than the pureof elastic limit than the pure metals from which they are derived. This explainsmetals from which they are derived. This explains why pure metals are rarely usedwhy pure metals are rarely used.. The hardening effect, known asThe hardening effect, known as solutionsolution hardeninghardening, is thought to be due to the fact that, is thought to be due to the fact that atoms of different atomic radii within the sameatoms of different atomic radii within the same lattice form a mechanical resistance to thelattice form a mechanical resistance to the movement of dislocations along slip planes.movement of dislocations along slip planes. www.indiandentalacademy.comwww.indiandentalacademy.com
  73. 73. Metals and alloys are sometimes characterizedMetals and alloys are sometimes characterized usingusing cooling curvescooling curves. The material is heated till. The material is heated till molten then allowed to cool and amolten then allowed to cool and a plot ofplot of temperature against timetemperature against time is recorded.is recorded.  Super coolingSuper cooling  Heterogeneous NucleationHeterogeneous Nucleation www.indiandentalacademy.comwww.indiandentalacademy.com
  74. 74. www.indiandentalacademy.comwww.indiandentalacademy.com
  75. 75.  Each alloy grain can be envisaged as having aEach alloy grain can be envisaged as having a concentration of gradient metals; the higherconcentration of gradient metals; the higher melting metal being concentrated close to themelting metal being concentrated close to the nucleus and the lower melting metal close to thenucleus and the lower melting metal close to the grain boundaries. The material is said to have agrain boundaries. The material is said to have a cored structure..  SuchSuch coring may influencemay influence corrosion resistancecorrosion resistance sincesince electrolytic cellselectrolytic cells may be set up on themay be set up on the surface of the alloy between areas of differentsurface of the alloy between areas of different alloy composition.alloy composition. www.indiandentalacademy.comwww.indiandentalacademy.com
  76. 76. Since coring may markedly reduce the corrosionSince coring may markedly reduce the corrosion resistance of some alloys, aresistance of some alloys, a heat treatmentheat treatment isis some times used to eliminate the cored structure.some times used to eliminate the cored structure. Such a heat treatment is termed aSuch a heat treatment is termed a homogenizationhomogenization heat treatmentheat treatment.. This involvesThis involves heating the alloyheating the alloy to a temperatureto a temperature just below the solidus temperaturejust below the solidus temperature for a fewfor a few minutes to allow diffusion of atoms and theminutes to allow diffusion of atoms and the establishment of homogeneous structure. Theestablishment of homogeneous structure. The alloy is then normallyalloy is then normally quenchedquenched in order toin order to prevent grain growthprevent grain growth from occurring.from occurring. E.g., Au-Ag system.E.g., Au-Ag system. www.indiandentalacademy.comwww.indiandentalacademy.com
  77. 77. If the temperaturesIf the temperatures TT11 andand TT22 are obtained overare obtained over a range of compositions for ana range of compositions for an alloy systemalloy system andand their values plotted against percentagetheir values plotted against percentage composition, acomposition, a useful graph emergesuseful graph emerges.. www.indiandentalacademy.comwww.indiandentalacademy.com
  78. 78. www.indiandentalacademy.comwww.indiandentalacademy.com
  79. 79. This is illustrated for aThis is illustrated for a hypothetical solid solutionhypothetical solid solution alloyalloy ofof metals Ametals A andand BB. The melting points of the pure metals. The melting points of the pure metals are indicated by the temperaturesare indicated by the temperatures TTmAmA andand TTmBmB. The. The upper and lower temperature limits of the crystallizationupper and lower temperature limits of the crystallization range,range, TT11 andand TT22 are shown for four alloys ranging inare shown for four alloys ranging in composition fromcomposition from 80% A80% A –– 20% B20% B toto 20% A20% A -- 80% B80% B.. www.indiandentalacademy.comwww.indiandentalacademy.com
  80. 80. www.indiandentalacademy.comwww.indiandentalacademy.com
  81. 81. TheThe phase diagramphase diagram is completed byis completed by joiningjoining together all thetogether all the T1 pointsT1 points and all theand all the T2 pointsT2 points,, together with the melting points of the puretogether with the melting points of the pure metals,metals, TTmAmA andand TTmBmB.. At temperatures in the region above the top line,At temperatures in the region above the top line, known as theknown as the liquidus line, the alloy is, the alloy is totallytotally liquidliquid. At temperatures in the region below the. At temperatures in the region below the bottom line, known as thebottom line, known as the Solidus line,, the alloythe alloy isis totally solidtotally solid.. www.indiandentalacademy.comwww.indiandentalacademy.com
  82. 82. www.indiandentalacademy.comwww.indiandentalacademy.com
  83. 83. At temperatures in the regionAt temperatures in the region betweenbetween the solidusthe solidus and liquidus lines the alloy consists of aand liquidus lines the alloy consists of a mixturemixture of solid and liquidof solid and liquid. The composition of the solid. The composition of the solid and liquid phases at any temperature betweenand liquid phases at any temperature between TT11 andand TT22 can be predicted with the aid of thecan be predicted with the aid of the phasephase diagram.diagram. www.indiandentalacademy.comwww.indiandentalacademy.com
  84. 84. When two metals areWhen two metals are completely misciblecompletely miscible inin liquid state, they are capable of forming anyliquid state, they are capable of forming any alloy. When such a combination isalloy. When such a combination is cooledcooled, one, one of the three possibilities may take place :of the three possibilities may take place : a)a) SSolid solutionolid solution b)b) IIntermetallic compoundntermetallic compound c)c) EEutectic formationutectic formation www.indiandentalacademy.comwww.indiandentalacademy.com
  85. 85. Intermetallic compoundsIntermetallic compounds Chemicals withChemicals with chemical affinitychemical affinity for each otherfor each other can form intermetallic compounds.can form intermetallic compounds. E.g.,E.g., Ag3SnAg3Sn can be formed between silver andcan be formed between silver and tin, which is antin, which is an essential constituentessential constituent ofof DENTAL AMALGAM ALLOYSDENTAL AMALGAM ALLOYS.. www.indiandentalacademy.comwww.indiandentalacademy.com
  86. 86. Eutectic mixtureEutectic mixture They occur when the metals areThey occur when the metals are miscible in themiscible in the liquid stateliquid state but separate in the solid statebut separate in the solid state. The. The two metals will be precipitated astwo metals will be precipitated as very finevery fine layers of one metal over the other onelayers of one metal over the other one : such a: such a combination as is called ancombination as is called an eutectic mixtureeutectic mixture.. E.g.,E.g.,72 %72 % silver,silver, 28 %28 % copper.copper. www.indiandentalacademy.comwww.indiandentalacademy.com
  87. 87. Phase diagramPhase diagram for a Binary system where therefor a Binary system where there Is complete solid insolubility.Is complete solid insolubility.  CEF  CDEGF  ‘E’ www.indiandentalacademy.comwww.indiandentalacademy.com
  88. 88. A material of this composition is called aA material of this composition is called a ““Eutectic alloy””  Important featuresImportant features ::  HardHard andand BrittleBrittle  Lowest meltingLowest melting alloy of the system -alloy of the system - solderssolders  PoorPoor corrosion resistancecorrosion resistance  Time-temperature curveTime-temperature curve for this alloy has afor this alloy has a ““Horizontal plateauHorizontal plateau” (like that of a” (like that of a pure metalpure metal)) www.indiandentalacademy.comwww.indiandentalacademy.com
  89. 89. Peritectic alloysPeritectic alloys Limited solubilityLimited solubility of two metals can lead to aof two metals can lead to a transformation referred as “transformation referred as “Peritectic transformationPeritectic transformation”” E.g.,E.g., Ag-SnAg-Sn (Basis for the original Dental Amalgam alloy, is a(Basis for the original Dental Amalgam alloy, is a Peritectic systemPeritectic system)) Invariant reactionInvariant reaction occurs at particularoccurs at particular temperaturetemperature andand composition.composition. www.indiandentalacademy.comwww.indiandentalacademy.com
  90. 90. CLASSIFICATIONCLASSIFICATION OFOF METALS AND ALLOY SYSTEMSMETALS AND ALLOY SYSTEMS www.indiandentalacademy.comwww.indiandentalacademy.com
  91. 91. Metals can beMetals can be broadlybroadly classified according toclassified according to composition ascomposition as NOBLE METALSNOBLE METALS The termThe term noblenoble identifies elements in terms of theiridentifies elements in terms of their chemical stabilitychemical stability i.e., theyi.e., they resist oxidationresist oxidation and areand are impervious to acidsimpervious to acids.. GGold,old, PPlatinum,latinum, PPalladium,alladium, RRhodium,hodium, RRuthenium,uthenium, IIridium,ridium, OOsmium, andsmium, and SSilver are theilver are the eight nobleeight noble metals.metals.  In the oral cavityIn the oral cavity Silver is more reactiveSilver is more reactive andand therefore istherefore is not considerednot considered as a noble metal.as a noble metal. www.indiandentalacademy.comwww.indiandentalacademy.com
  92. 92. PRECIOUS METALSPRECIOUS METALS The term “The term “preciousprecious” merely indicates whether a” merely indicates whether a metal hasmetal has intrinsic valueintrinsic value, the noble metals (all eight), the noble metals (all eight) are also precious metals and are defined as such byare also precious metals and are defined as such by majormajor metallurgical societiesmetallurgical societies and theand the federalfederal government agenciesgovernment agencies likelike National institute ofNational institute of science and technology.science and technology.  All noble metals are preciousAll noble metals are precious butbut all precious metalsall precious metals are not nobleare not noble..  SilverSilver is usually the major ingredient in most alloysis usually the major ingredient in most alloys considered asconsidered as preciousprecious.. www.indiandentalacademy.comwww.indiandentalacademy.com
  93. 93. SEMIPRECIOUS METALSSEMIPRECIOUS METALS There isThere is no accepted compositionno accepted composition that differentiatesthat differentiates “precious from semiprecious” therefore, this“precious from semiprecious” therefore, this termterm isis usuallyusually avoided.avoided. www.indiandentalacademy.comwww.indiandentalacademy.com
  94. 94. BASE METALS These areThese are IgnobleIgnoble elements. These remainelements. These remain invaluable componentsinvaluable components ofof dental casting alloysdental casting alloys because of their influence onbecause of their influence on physical propertiesphysical properties,, control of the amountcontrol of the amount andand type of oxidationtype of oxidation, or, or for theirfor their strengthening effectsstrengthening effects.. e.g., Chromium,e.g., Chromium, CCobalt,obalt, NNickel,ickel, IIron,ron, CCopperopper etc.etc. www.indiandentalacademy.comwww.indiandentalacademy.com
  95. 95. The bureau of standards establishedThe bureau of standards established gold casting alloysgold casting alloys type i through type ivtype i through type iv according to function, withaccording to function, with increasing hardnessincreasing hardness from type i to iv (from type i to iv (19271927)) www.indiandentalacademy.comwww.indiandentalacademy.com
  96. 96. InIn 19841984,, ADAADA proposed a simple classification forproposed a simple classification for Dental casting alloysDental casting alloys www.indiandentalacademy.comwww.indiandentalacademy.com
  97. 97. Alloy types by description www.indiandentalacademy.comwww.indiandentalacademy.com
  98. 98. www.indiandentalacademy.comwww.indiandentalacademy.com
  99. 99. Removable partial denture alloysRemovable partial denture alloys Although type IV noble metal alloys may beAlthough type IV noble metal alloys may be used, majority of the removable partial frameused, majority of the removable partial frame works are made from base metal alloys.works are made from base metal alloys. E.g.,E.g., CCobalt-obalt-cchromium,hromium, NNickel-ickel-cchromium.hromium. www.indiandentalacademy.comwww.indiandentalacademy.com
  100. 100. DENTAL CASTING ALLOYS The history of dental casting alloys has beenThe history of dental casting alloys has been influenced byinfluenced by threethree major factors.major factors. a)a) TThe technological changes of dental prosthesis.he technological changes of dental prosthesis. b)b) MMetallurgic advancementsetallurgic advancements c)c) PPrice changes of noble metals sincerice changes of noble metals since19681968.. InIn 19321932, the dental materials group at national, the dental materials group at national bureau of standards surveyed thebureau of standards surveyed the alloysalloys being usedbeing used and roughly classified themand roughly classified them typetype I-IVI-IV.. www.indiandentalacademy.comwww.indiandentalacademy.com
  101. 101. UsesUses 1)1) Fabrication of inlay, onlaysFabrication of inlay, onlays 2)2) Fabrication of crowns, conventional all metalFabrication of crowns, conventional all metal bridges, metal-ceramic bridges, resin bondedbridges, metal-ceramic bridges, resin bonded bridges.bridges. 3)3) Endodontic posts.Endodontic posts. 4)4) Removable partial denture frameworks.Removable partial denture frameworks. www.indiandentalacademy.comwww.indiandentalacademy.com
  102. 102. Desirable propertiesDesirable properties 1) Biocompatibility.1) Biocompatibility. 2) Ease of melting.2) Ease of melting. 3) Ease of casting, brazing and polishing.3) Ease of casting, brazing and polishing. 4) Less solidification shrinkage.4) Less solidification shrinkage. 5) Minimal reactivity with the mould material.5) Minimal reactivity with the mould material. 6) Good wear resistance.6) Good wear resistance. 7) High strength and sag resistance.7) High strength and sag resistance. 8) Excellent tarnish and corrosion resistance.8) Excellent tarnish and corrosion resistance.www.indiandentalacademy.comwww.indiandentalacademy.com
  103. 103. Nickel-chromium and Cobalt-chromium Alloys Dental applications:Dental applications: 1)1) Partial denture framework:Partial denture framework: Co-CrCo-Cr,, Ni-CrNi-Cr 2)2) Porcelain - metal restorations:Porcelain - metal restorations: Co-CrCo-Cr,, Ni-CrNi-Cr 3)3) Crowns and bridges:Crowns and bridges: Ni-CrNi-Cr www.indiandentalacademy.comwww.indiandentalacademy.com
  104. 104. During the years since theDuring the years since the Co-Cr casting alloysCo-Cr casting alloys became available for cast removable partialbecame available for cast removable partial denture constructions, they have continued todenture constructions, they have continued to increase inincrease in popularitypopularity.. www.indiandentalacademy.comwww.indiandentalacademy.com
  105. 105. Function of various alloying elements:Function of various alloying elements: • Chromium is responsible for theChromium is responsible for the tarnish resistancetarnish resistance and stainless properties of these alloys.and stainless properties of these alloys. • When chromium content of alloy is overWhen chromium content of alloy is over 30%30% , the, the alloy isalloy is difficultdifficult to cast. With this percentage ofto cast. With this percentage of chromium, the alloy also forms achromium, the alloy also forms a brittle phasebrittle phase, known, known asas sigma phasesigma phase. Therefore cast base metal dental. Therefore cast base metal dental alloys shouldalloys should notnot contain more thancontain more than 28-29%28-29% ofof chromium.chromium. www.indiandentalacademy.comwww.indiandentalacademy.com
  106. 106. • CobaltCobalt increases the elastic modulus, strength andincreases the elastic modulus, strength and hardness of alloy more than does nickel.hardness of alloy more than does nickel. • One of the effective ways of increasing their hardness isOne of the effective ways of increasing their hardness is byby alteringaltering carbon content.carbon content. 0.2% increase0.2% increase changes the properties such thatchanges the properties such that alloy would no longer be used in dentistry.alloy would no longer be used in dentistry. [[Too brittleToo brittle]] 0.2% decrease0.2% decrease willwill reducereduce yield and ultimateyield and ultimate tensile and yield strengths.tensile and yield strengths. www.indiandentalacademy.comwww.indiandentalacademy.com
  107. 107. • AluminumAluminum in nickel containing alloysin nickel containing alloys increasesincreases thethe ultimate tensile and yield strengths.ultimate tensile and yield strengths. MicrostructureMicrostructure Microstructure of any substance is the basicMicrostructure of any substance is the basic parameter thatparameter that controls the propertiescontrols the properties. In other words,. In other words, aa change in the physical propertieschange in the physical properties of material is aof material is a strong indication that there must have been somestrong indication that there must have been some alteration in its microstructure.alteration in its microstructure. www.indiandentalacademy.comwww.indiandentalacademy.com
  108. 108. The microstructure of Co-Cr alloys in the castThe microstructure of Co-Cr alloys in the cast condition is incondition is in homogeneoushomogeneous, consisting of an, consisting of an austenitic matrixaustenitic matrix composed of a solid solution ofcomposed of a solid solution of cobalt and chromium in a casedcobalt and chromium in a cased dendriticdendritic structurestructure. The dendritic regions are. The dendritic regions are cobalt-richcobalt-rich,, where as the interdendritic regions can be awhere as the interdendritic regions can be a quaternary mixture.quaternary mixture. www.indiandentalacademy.comwww.indiandentalacademy.com
  109. 109. ThreeThree mainmain disadvantagesdisadvantages in employing these alloysin employing these alloys ((Co-CrCo-Cr)) Clasps made of such alloysClasps made of such alloys break in servicebreak in service; some; some break after relatively short time.break after relatively short time. Due to relativelyDue to relatively high hardnesshigh hardness andand low elongationlow elongation properties of these alloys someproperties of these alloys some minorminor but necessarybut necessary adjustmentsadjustments needed at the time of delivery areneeded at the time of delivery are difficult and also willdifficult and also will consumeconsume the chair time ofthe chair time of dentist.dentist. Due to theirDue to their high degree of hardnesshigh degree of hardness, the, the teethteeth contacting the metal becomescontacting the metal becomes wornworn easily.easily. www.indiandentalacademy.comwww.indiandentalacademy.com
  110. 110. MorrisMorris 19751975 stated thatstated that Co-Cr alloysCo-Cr alloys areare harderharder than iron base alloys .than iron base alloys . InIn 19791979, he stated that, he stated that heat treatmentheat treatment decreasesdecreases strengthstrength of the alloy compared to Au-Pd alloys.of the alloy compared to Au-Pd alloys. J.C. Wataha et.alJ.C. Wataha et.al,, 19921992 stated thatstated that preparativepreparative proceduresprocedures such as steam sterilization,such as steam sterilization, irradiation, plasma treatment and acid treatmentirradiation, plasma treatment and acid treatment altered the surfacealtered the surface of alloys.of alloys. www.indiandentalacademy.comwww.indiandentalacademy.com
  111. 111. InIn 19741974,, A C RoweA C Rowe stated that addingstated that adding TantalumTantalum (13%)(13%) to a Co-Cr-Ni alloy the properties like ultimateto a Co-Cr-Ni alloy the properties like ultimate tensile strength, yield strength are increased by 12-tensile strength, yield strength are increased by 12- 13%.13%. Tantalum reduces dislocationsTantalum reduces dislocations, a, a well orderedwell ordered structurestructure is formed. Tantalum is ais formed. Tantalum is a stabilizerstabilizer. Example. Example for stabilizers arefor stabilizers are carbon, molybdenum, tungsten.carbon, molybdenum, tungsten. Hamid MohammadHamid Mohammad andand Kamal asgarKamal asgar 19731973, indicated, indicated that a cobalt made from 40% Co, 30% Ni, 30% Crthat a cobalt made from 40% Co, 30% Ni, 30% Cr strengthenedstrengthened by precipitation of coherent Intermetallicby precipitation of coherent Intermetallic compounds of Tantalum.compounds of Tantalum. www.indiandentalacademy.comwww.indiandentalacademy.com
  112. 112. They also haveThey also have criteriacriteria to select an additional elementto select an additional element 1)1) CCorrosion resistance.orrosion resistance. 2)2) RResistance to oxidation during alloying.esistance to oxidation during alloying. 3)3) EEfficiency as a nucleating agent during solidification.fficiency as a nucleating agent during solidification. 4)4) EEfficiency as a solid solution hardener.fficiency as a solid solution hardener. 5)5) FFineness of precipitate.ineness of precipitate. 6)6) CCoherency.oherency. www.indiandentalacademy.comwww.indiandentalacademy.com
  113. 113. Titanium And Titanium Alloys:Titanium And Titanium Alloys: Titanium’sTitanium’s resistance to electrochemicalresistance to electrochemical degradationdegradation; the; the benign biological responsebenign biological response that itthat it elicits; itselicits; its relatively low weightrelatively low weight; and its; and its lowlow densitydensity,, low moduluslow modulus, and, and high strengthhigh strength makemake titanium based materials attractive for use intitanium based materials attractive for use in dentistry.dentistry. www.indiandentalacademy.comwww.indiandentalacademy.com
  114. 114. Ti forms a veryTi forms a very stable oxidestable oxide layer with a thicknesslayer with a thickness on the order of angstroms and iton the order of angstroms and it repassivatesrepassivates in ain a time on the order of nanoseconds. This oxidetime on the order of nanoseconds. This oxide formation is the basis for theformation is the basis for the corrosion resistancecorrosion resistance andand biocompatibilitybiocompatibility of Ti.of Ti. Commercially Pure TitaniumCommercially Pure Titanium ((CpTiCpTi) is used for) is used for fabricatingfabricating dental implantsdental implants, and more recently, as, and more recently, as crowns, partial and complete dentures,crowns, partial and complete dentures, andand orthodontic wiresorthodontic wires.. Wrought alloys of Ti and V and of Ti and Mo areWrought alloys of Ti and V and of Ti and Mo are used for orthodontic wires.used for orthodontic wires. www.indiandentalacademy.comwww.indiandentalacademy.com
  115. 115. Commercially pure Ti is available inCommercially pure Ti is available in 4 grades4 grades whichwhich vary according to thevary according to the OxygenOxygen (0.18-0.40 wt%) and(0.18-0.40 wt%) and ironiron (0.2-0.5 wt%) contents.(0.2-0.5 wt%) contents. At room temperature CpTi has aAt room temperature CpTi has a HCHCPP crystal latticecrystal lattice,, which is denoted as thewhich is denoted as the alpha phasealpha phase. On beating, an. On beating, an allotropic phase transformation occurs, at 883°c, aallotropic phase transformation occurs, at 883°c, a BCCBCC phase, which is denoted as thephase, which is denoted as the beta(beta(ββ)) phasephase forms.forms. A component with aA component with a predominantly beta phasepredominantly beta phase isis strongerstronger but morebut more brittlebrittle than a component with an alphathan a component with an alpha phase microstructure,phase microstructure, www.indiandentalacademy.comwww.indiandentalacademy.com
  116. 116. Titanium alloys Pure titanium is of two types –Pure titanium is of two types –  Grade IGrade I  Grade II.Grade II. Alloying elementsAlloying elements areare added to stabilizeadded to stabilize either theeither the αα oror ββ phase by changingphase by changing ββ toto αα transportationtransportation temperature.temperature. www.indiandentalacademy.comwww.indiandentalacademy.com
  117. 117. ForFor exampleexample, in, in Ti 6 Al-4VTi 6 Al-4V,, aluminumaluminum is anis an αα stabilizer, which expands thestabilizer, which expands the αα phase field byphase field by increasing the (increasing the (αα ++ ββ) to) to ββ transformation temperature.transformation temperature. VanadiumVanadium, as well as, as well as coppercopper andand palladiumpalladium areare ββ stabilizers, which expand the ‘stabilizers, which expand the ‘ββ’’ - phase field by- phase field by decreasing (decreasing (αα ++ ββ) transformation temperature.) transformation temperature. www.indiandentalacademy.comwww.indiandentalacademy.com
  118. 118. Ti-6Al-4VTi-6Al-4V  MostMost widelywidely used.used.  At room temperature, Ti-6 Al-4V is a two phaseAt room temperature, Ti-6 Al-4V is a two phase αα ++ββ alloy.alloy.  At approximately 975 °C an allotropic phaseAt approximately 975 °C an allotropic phase transformation takes place, transforming thetransformation takes place, transforming the microstructure to a single phase BCCmicrostructure to a single phase BCC ββ alloy.alloy.  Mostly used forMostly used for surgical implantssurgical implants.. www.indiandentalacademy.comwww.indiandentalacademy.com
  119. 119. Based on attributes, extensive knowledge, and clinicalBased on attributes, extensive knowledge, and clinical success ofsuccess of wrought Ti implantswrought Ti implants, interest was developed, interest was developed inin cast titanium for dental applications.cast titanium for dental applications. TheThe twotwo most important factors in casting Titaniummost important factors in casting Titanium based materials are thebased materials are the high melting pointhigh melting point andand chemical reactivitychemical reactivity.. Cast Titanium:Cast Titanium: www.indiandentalacademy.comwww.indiandentalacademy.com
  120. 120. Ti readilyTi readily reactsreacts with gaseous elements such aswith gaseous elements such as hydrogen, oxygenhydrogen, oxygen andand nitrogennitrogen particularly atparticularly at highhigh temperaturestemperatures. So any manipulation of Ti at. So any manipulation of Ti at elevatedelevated temperaturestemperatures must be performed in amust be performed in a well-controlledwell-controlled vaccumvaccum, Without a well controlled vaccum, Ti surfaces, Without a well controlled vaccum, Ti surfaces will bewill be contaminatedcontaminated with anwith an oxygen enriched andoxygen enriched and hardened surface layerhardened surface layer, which can be as thick as, which can be as thick as 100100 µmµm.. surface layers of this thicknesssurface layers of this thickness reduce strengthreduce strength andand ductility andductility and promote crackingpromote cracking because ofbecause of embrittlingembrittling effecteffect of oxygen.of oxygen. www.indiandentalacademy.comwww.indiandentalacademy.com
  121. 121. Because of theBecause of the high affinityhigh affinity Titanium has forTitanium has for hydrogen, oxygen and nitrogenhydrogen, oxygen and nitrogen,, standard crucibles andstandard crucibles and investment materialsinvestment materials cannotcannot be used.be used. Investment materialsInvestment materials must havemust have oxides that are moreoxides that are more stable than the very stable Ti oxidestable than the very stable Ti oxide and must also beand must also be able to withstand a temperature sufficient to meltable to withstand a temperature sufficient to melt titanium. if this is not the case, thentitanium. if this is not the case, then diffusion ofdiffusion of oxygenoxygen into the molten is likely to occur.into the molten is likely to occur. www.indiandentalacademy.comwww.indiandentalacademy.com
  122. 122. Investment materials such as phosphate bondedInvestment materials such as phosphate bonded silica and phosphate investment materials withsilica and phosphate investment materials with added trace elementsadded trace elements achieve this goal. It hasachieve this goal. It has been shown that withbeen shown that with magnesium oxide-basedmagnesium oxide-based investments, internal porosity resultsinvestments, internal porosity results.. www.indiandentalacademy.comwww.indiandentalacademy.com
  123. 123.  Because of the low density of titanium, it is difficultBecause of the low density of titanium, it is difficult to cast. In the last 10 to 15 yrs, advanced castingto cast. In the last 10 to 15 yrs, advanced casting techniques, which combine centrifugation, vaccumtechniques, which combine centrifugation, vaccum pressure and gravity casing, and new investmentpressure and gravity casing, and new investment materials are used.materials are used.  Properties of Alloyed TitaniumProperties of Alloyed Titanium 1)1) Lower melting points compared to pure Ti, but sameLower melting points compared to pure Ti, but same as as Ni-Cr or Co-Cr alloys.as as Ni-Cr or Co-Cr alloys. 2)2) Mechanical properties of cast CPTi are similar toMechanical properties of cast CPTi are similar to those of type III and IV gold alloys.those of type III and IV gold alloys.www.indiandentalacademy.comwww.indiandentalacademy.com
  124. 124. Other alloysOther alloys  Ti-15V, Ti-20Cu, Ti-30pd,Ti-15V, Ti-20Cu, Ti-30pd, Ti-Co, Ti-Cu.Ti-Co, Ti-Cu. DisadvantagesDisadvantages ((for dental purposefor dental purpose)) a)a) HHigh melting point.igh melting point. b)b) HHigh reactivity.igh reactivity. c)c) LLow casting efficiency.ow casting efficiency. d)d) IInadequate expansion of investment.nadequate expansion of investment. e)e) CCasting porosity.asting porosity. www.indiandentalacademy.comwww.indiandentalacademy.com
  125. 125. f)f) DDifficulty in finishing this metal.ifficulty in finishing this metal. g)g) DDifficult to weld, solder.ifficult to weld, solder. h)h) EExpensive equipment.xpensive equipment. www.indiandentalacademy.comwww.indiandentalacademy.com
  126. 126. Aluminum Bronze alloyAluminum Bronze alloy Traditionally bronze isTraditionally bronze is copper-rich copper tincopper-rich copper tin.. CompositionComposition of ADA approved alloy of this group hasof ADA approved alloy of this group has 81-88% copper81-88% copper 7-11% wt aluminum7-11% wt aluminum 2-4% nickel2-4% nickel 1-4% iron.1-4% iron. DisadvantageDisadvantage:: Copper reacts with sulfur to formCopper reacts with sulfur to form copper sulfidecopper sulfide,, whichwhich tarnishestarnishes the surface of this alloy.the surface of this alloy. www.indiandentalacademy.comwww.indiandentalacademy.com
  127. 127. METAL CERAMIC RESTORATIONS:METAL CERAMIC RESTORATIONS: TheThe chief objectionchief objection to the use of dental porcelainto the use of dental porcelain as a restorative material is itsas a restorative material is its low tensilelow tensile andand shearshear strength. Thisstrength. This can be minimized by bondingcan be minimized by bonding porcelain directly to aporcelain directly to a cast alloy substructurecast alloy substructure mademade to fit the prepared tooth. If a strong bond isto fit the prepared tooth. If a strong bond is attained between the porcelain veneers and theattained between the porcelain veneers and the metal, the porcelain veneer is reinforced.metal, the porcelain veneer is reinforced. www.indiandentalacademy.comwww.indiandentalacademy.com
  128. 128. The original metal ceramic alloys containedThe original metal ceramic alloys contained 88%88% goldgold and were much too soft for stress-bearingand were much too soft for stress-bearing restorations. As there wasrestorations. As there was no evidence of ano evidence of a chemical bondchemical bond between these alloys and dentalbetween these alloys and dental porcelain, thenporcelain, then mechanical retentionmechanical retention andand undercutsundercuts were used to prevent detachment of the ceramicwere used to prevent detachment of the ceramic veneer. By addingveneer. By adding lessless thanthan 1% of oxide elements1% of oxide elements such as iron, indium and tin to this high-goldsuch as iron, indium and tin to this high-gold content alloy, the porcelain metal bond strengthcontent alloy, the porcelain metal bond strength was improved bywas improved by three foldsthree folds.. www.indiandentalacademy.comwww.indiandentalacademy.com
  129. 129. Classification of alloysClassification of alloys used for metal ceramic restorations:used for metal ceramic restorations: High nobleHigh noble  Au-Pt-PdAu-Pt-Pd  Au-Pd-AgAu-Pd-Ag  Au-PdAu-Pd NobleNoble  Pd-AuPd-Au  Pd-Au-AgPd-Au-Ag  Pd-AgPd-Ag Base metalBase metal  Pure Ti, Ni-Cr-Mo-Be, Ti-Al-V, Ni-Cr-MoPure Ti, Ni-Cr-Mo-Be, Ti-Al-V, Ni-Cr-Mo www.indiandentalacademy.comwww.indiandentalacademy.com
  130. 130. Inspite ofInspite of vastly different chemical compositionsvastly different chemical compositions,, all alloys share at leastall alloys share at least threethree common features:common features:  They have the potential to bond to dentalThey have the potential to bond to dental porcelain.porcelain.  They possess co-efficient of thermal contractionThey possess co-efficient of thermal contraction compatible with those of dental porcelains.compatible with those of dental porcelains.  Their solidus temperature is sufficiently high toTheir solidus temperature is sufficiently high to permit the application of low-fusing porcelains.permit the application of low-fusing porcelains. www.indiandentalacademy.comwww.indiandentalacademy.com
  131. 131. The following high noble alloys are usedThe following high noble alloys are used Gold based metal ceramic alloysGold based metal ceramic alloys These have aThese have a goldgold content ranging up tocontent ranging up to 88%88% withwith varying amounts of Pd, Pt and small amounts ofvarying amounts of Pd, Pt and small amounts of base metals. Alloys of this type are restricted tobase metals. Alloys of this type are restricted to Three unit spansThree unit spans,, anterior cantileveranterior cantilever oror crownscrowns.. www.indiandentalacademy.comwww.indiandentalacademy.com
  132. 132. Gold-Palladium Silver alloysGold-Palladium Silver alloys The gold based alloys contain between 39% and 77%The gold based alloys contain between 39% and 77% goldgold up to 35%up to 35% palladiumpalladium, and, and silversilver levels as high aslevels as high as 22%.22%. TheThe silversilver increasesincreases the thermal contraction co-efficientthe thermal contraction co-efficient but it also has a tendency tobut it also has a tendency to discolordiscolor some porcelains.some porcelains. www.indiandentalacademy.comwww.indiandentalacademy.com
  133. 133. Gold-Palladium alloysGold-Palladium alloys They have 44-55% ofThey have 44-55% of goldgold and 35-45% ofand 35-45% of PdPd.. Used withUsed with porcelainsporcelains havinghaving low co-efficient oflow co-efficient of thermal contractionthermal contraction toto avoidavoid the development ofthe development of axial and circumferential tensile stressesaxial and circumferential tensile stresses inin porcelain during the cooling part of the porcelainporcelain during the cooling part of the porcelain firing cycle.firing cycle. More economical than high gold alloys.More economical than high gold alloys. www.indiandentalacademy.comwww.indiandentalacademy.com
  134. 134. NOBLE ALLOYSNOBLE ALLOYS These areThese are Pd basedPd based alloys.alloys. These alloys were introduced in lateThese alloys were introduced in late 197O197O’s’s TheThe disadvantagedisadvantage was they had a tendency towas they had a tendency to discolordiscolor the porcelain during firingthe porcelain during firing This greenish-yellow discoloration, popularityThis greenish-yellow discoloration, popularity termed an “termed an “GREENINGGREENING” is due to the” is due to the silversilver vapour that escapes from the surface of thesevapour that escapes from the surface of these alloys during firing of the porcelainalloys during firing of the porcelain.. www.indiandentalacademy.comwww.indiandentalacademy.com
  135. 135. The silver vapour diffuses asThe silver vapour diffuses as ionic silverionic silver into theinto the porcelain, and is reduced formporcelain, and is reduced form colloidal metalliccolloidal metallic silversilver in the surface of porcelain.in the surface of porcelain. Some of the high palladium alloys develop a layer ofSome of the high palladium alloys develop a layer of dark oxidedark oxide on their surface during cooling fromon their surface during cooling from the degassing cycle, and this layer has proventhe degassing cycle, and this layer has proven difficult to mask by the opaque porcelain.difficult to mask by the opaque porcelain. www.indiandentalacademy.comwww.indiandentalacademy.com
  136. 136. CompositionComposition of Pd-Ag alloys fall within a narrowof Pd-Ag alloys fall within a narrow range 53% to 61% palladium and 28% 40%range 53% to 61% palladium and 28% 40% silver,silver, TinTin oror indiumindium or both are usually added toor both are usually added to increase alloy hardnessincrease alloy hardness and toand to promote oxidepromote oxide formationformation for adequate bonding of porcelain.for adequate bonding of porcelain. www.indiandentalacademy.comwww.indiandentalacademy.com
  137. 137. Palladium-Copper alloysPalladium-Copper alloys  Comparable inComparable in costcost to Pd-Ag alloys.to Pd-Ag alloys.  Susceptible toSusceptible to creepcreep deformation at elevated firingdeformation at elevated firing temperatures, sotemperatures, so attentionattention is given when these alloysis given when these alloys are used for long span FPD’s with small connectors.are used for long span FPD’s with small connectors.  Composition:Composition: 74-80% Palladium, 2-15% copper.74-80% Palladium, 2-15% copper.  PorcelainPorcelain discolorationdiscoloration due to copper isdue to copper is notnot a majora major problem.problem.  These have 1145 Mpa ofThese have 1145 Mpa of yield strength and hardnessyield strength and hardness valuesvalues equalequal toto base metal alloysbase metal alloys..  These have aThese have a poor potential for burnishingpoor potential for burnishing when thewhen the marginal areas are thinmarginal areas are thin www.indiandentalacademy.comwww.indiandentalacademy.com
  138. 138. Palladium-Cobalt alloysPalladium-Cobalt alloys  Comparable in cost to Pd-Ag alloys.Comparable in cost to Pd-Ag alloys.  Often advertised as gold free, nickel free, berylliumOften advertised as gold free, nickel free, beryllium free.free.  These have a fine grain size to minimize hot tearingThese have a fine grain size to minimize hot tearing during the solidification process.during the solidification process.  It is the most sag-resistance of all noble alloys.It is the most sag-resistance of all noble alloys.  Composition: 78-88% of Pd and 4-10% of Co.Composition: 78-88% of Pd and 4-10% of Co. www.indiandentalacademy.comwww.indiandentalacademy.com
  139. 139. Palladium-Gallium-Silver and Pa-Gallium-SilverPalladium-Gallium-Silver and Pa-Gallium-Silver Gold alloysGold alloys  These areThese are most recentmost recent alloys.alloys.  These have aThese have a slightly lighter coloredslightly lighter colored oxide thanoxide than the Pd-Cu or Pd-Co alloys and they are thermallythe Pd-Cu or Pd-Co alloys and they are thermally compatible with lower expansion porcelains.compatible with lower expansion porcelains.  Silver content is lowSilver content is low (5%) and is inadequate to(5%) and is inadequate to cause porcelain greening.cause porcelain greening.  AreAre compatiblecompatible with lower expansion porcelainswith lower expansion porcelains such as vita porcelain.such as vita porcelain. www.indiandentalacademy.comwww.indiandentalacademy.com
  140. 140. Physical properties of high noble and noble alloysPhysical properties of high noble and noble alloys::  Should have aShould have a high melting rangehigh melting range so that the metalso that the metal is solid well above the porcelain sinteringis solid well above the porcelain sintering temperature totemperature to minimize distortionminimize distortion of castingof casting during porcelain application.during porcelain application.  Must haveMust have considerably low fusing temperatureconsiderably low fusing temperature..  GoodGood corrosion resistance.corrosion resistance.  HighHigh modulus of elasticity.modulus of elasticity. www.indiandentalacademy.comwww.indiandentalacademy.com
  141. 141. Base metal alloysBase metal alloys Compared with ADA certifiedCompared with ADA certified type IVtype IV gold alloys.gold alloys. Cobalt based alloys, Nickel based alloys, and PureCobalt based alloys, Nickel based alloys, and Pure titanium have the followingtitanium have the following advantagesadvantages.. 1)1) LLow costow cost 2)2) LLow densityow density 3)3) GGreater stiffnessreater stiffness 4)4) HHigher hardnessigher hardness 5)5) HHigh resistance to tarnish and corrosion.igh resistance to tarnish and corrosion. www.indiandentalacademy.comwww.indiandentalacademy.com
  142. 142. CompositionComposition Co-CrCo-Cr  53-67% of cobalt53-67% of cobalt 25-32% of chromium25-32% of chromium 02-06 wt % molybdenum.02-06 wt % molybdenum. Ni-CrNi-Cr  61-81 wt % Nickel61-81 wt % Nickel 11-27% chromium11-27% chromium 02-05 wt of molybdenum.02-05 wt of molybdenum. ChromiumChromium providesprovides passivationpassivation andand corrosion resistancecorrosion resistance..www.indiandentalacademy.comwww.indiandentalacademy.com
  143. 143. Properties:Properties: 1)1) Higher hardness and stiffness.Higher hardness and stiffness. 2)2) More sag resistant at elevated temperatures.More sag resistant at elevated temperatures. 3)3) It is improbable than significant occlusal wear ofIt is improbable than significant occlusal wear of these alloys occur. Therefore, particular attentionthese alloys occur. Therefore, particular attention must be directed toward perfecting occlusalmust be directed toward perfecting occlusal equilibration.equilibration. 4)4) It deforms only less thanIt deforms only less than 2525 µmµm when porcelain iswhen porcelain is fired over it.fired over it. www.indiandentalacademy.comwww.indiandentalacademy.com
  144. 144. Metals for partial denture alloyMetals for partial denture alloy These are classified as:These are classified as: High nobleHigh noble Au-Ag-Cu-PdAu-Ag-Cu-Pd NobleNoble Ag-Pd-Au-CuAg-Pd-Au-Cu Ag-PdAg-Pd Base MetalBase Metal Pure Ti, Ti-Al-V,Pure Ti, Ti-Al-V, Ni-Cr-Mo-Be, Ni-Cr-Mo, Co-Cr-Mo.Ni-Cr-Mo-Be, Ni-Cr-Mo, Co-Cr-Mo. www.indiandentalacademy.comwww.indiandentalacademy.com
  145. 145. Properties requiredProperties required  HHigh tarnish - corrosion resistanceigh tarnish - corrosion resistance  SShould be easily castablehould be easily castable  GGood modulus of elasticity, which is a measure ofood modulus of elasticity, which is a measure of stiffness and rigidity. It helps in determiningstiffness and rigidity. It helps in determining thickness of various portions of framework.thickness of various portions of framework.  SShould have high strength and hardness.hould have high strength and hardness.  DDuctility should be higher which represents auctility should be higher which represents a measure of amount of plastic deformation that ameasure of amount of plastic deformation that a denture framework can withstand before itdenture framework can withstand before it fractures.fractures. www.indiandentalacademy.comwww.indiandentalacademy.com
  146. 146. WROUGHT BASE METAL AND GOLD ALLOYS:  When a casting isWhen a casting is plastically deformedplastically deformed in anyin any manner, it is calledmanner, it is called wrought metalwrought metal..  Wrought base metal alloys are used in dentistry,Wrought base metal alloys are used in dentistry, mainly asmainly as wireswires forfor orthodonticsorthodontics and asand as clasp armsclasp arms forfor removable partial denturesremovable partial dentures.. The alloys include:The alloys include: Stainless steel : iron-chromium-nickel alloyStainless steel : iron-chromium-nickel alloy Co-Cr-NiCo-Cr-Ni Ni-TiNi-Ti ββ- Titanium alloys.- Titanium alloys.www.indiandentalacademy.comwww.indiandentalacademy.com
  147. 147. CARBON STEELS: Steels areSteels are iron based alloysiron based alloys that usually containthat usually contain lessless than 1.2% carbonthan 1.2% carbon.. The different classes of steels are based onThe different classes of steels are based on threethree possible lattice arrangementspossible lattice arrangements of iron.of iron. www.indiandentalacademy.comwww.indiandentalacademy.com
  148. 148. www.indiandentalacademy.comwww.indiandentalacademy.com
  149. 149. STAINLESSSTAINLESS STEELSTEEL When 12-30% Cr is added to steel, the alloy is called asWhen 12-30% Cr is added to steel, the alloy is called as Stainless steelStainless steel www.indiandentalacademy.comwww.indiandentalacademy.com
  150. 150. Ferritic stainless steel:Ferritic stainless steel:  Often designated as American Iron and SteelOften designated as American Iron and Steel institute (institute (AISIAISI) series 400 stainless steels.) series 400 stainless steels.  GoodGood corrosion resistance.corrosion resistance.  IsIs notnot hardenable by heat treatment.hardenable by heat treatment.  LimitedLimited application in dentistry.application in dentistry. www.indiandentalacademy.comwww.indiandentalacademy.com
  151. 151. Martensitic stainless steel:Martensitic stainless steel:  Share theShare the AISI 400AISI 400 designation.designation.  Have high strength and hardness, so used forHave high strength and hardness, so used for surgicalsurgical andand cutting instruments.cutting instruments.  PoorPoor corrosion resistance.corrosion resistance. www.indiandentalacademy.comwww.indiandentalacademy.com
  152. 152. Austenitic stainless steel:Austenitic stainless steel:  Most corrosion resistantMost corrosion resistant of all.of all.  AISI 302AISI 302 is basic type, containing 18% or 8%is basic type, containing 18% or 8% NiNi and 0.15%and 0.15% carboncarbon..  Type 304Type 304 has 0.08% of carbon.has 0.08% of carbon.  Both are designated asBoth are designated as 18-8 stainless steel18-8 stainless steel  TypeType 316L316L (0.03% carbon) is ordinarily employed(0.03% carbon) is ordinarily employed forfor implantsimplants.. www.indiandentalacademy.comwww.indiandentalacademy.com
  153. 153. Generally austenite stainless steel is preferable toGenerally austenite stainless steel is preferable to ferritic because of the following characteristics.ferritic because of the following characteristics. 1)1) Greater ductilityGreater ductility andand ability to undergo cold workability to undergo cold work without fracturing.without fracturing. 2)2) Substantial strengtheningSubstantial strengthening during cold working.during cold working. 3)3) Greater ease of weldingGreater ease of welding.. 4)4) AbilityAbility to fairly readily overcome sensitization.to fairly readily overcome sensitization. 5)5) Less critical grain growthLess critical grain growth.. 66) Comparative ease) Comparative ease in forming.in forming. www.indiandentalacademy.comwww.indiandentalacademy.com
  154. 154. CORROSION RESISTANCE:CORROSION RESISTANCE:  The 18-8 stainless steel mayThe 18-8 stainless steel may loselose itsits resistance toresistance to corrosioncorrosion if it is heated betweenif it is heated between 400°C and 900°C400°C and 900°C..  The reason for a decrease in corrosion is theThe reason for a decrease in corrosion is the precipitation ofprecipitation of chromium carbidechromium carbide at the grainat the grain boundaries at high temperature. The small, rapidlyboundaries at high temperature. The small, rapidly diffusing carbon atoms migrate to graindiffusing carbon atoms migrate to grain boundaries from all parts of the crystal to combineboundaries from all parts of the crystal to combine with the large, slowly diffusing chromium atomswith the large, slowly diffusing chromium atoms at the periphery of the grain, where energy isat the periphery of the grain, where energy is highest.highest. www.indiandentalacademy.comwww.indiandentalacademy.com
  155. 155. WhenWhen chromium combines with the carbonchromium combines with the carbon in thisin this manner, itsmanner, its passivating qualities are lostpassivating qualities are lost, and, as a, and, as a consequence,consequence, corrosion resistancecorrosion resistance of the steel isof the steel is reducedreduced.. Because that portion of grain adjacent to grainBecause that portion of grain adjacent to grain boundary is generally depleted to produceboundary is generally depleted to produce chromium carbide,chromium carbide, intergranular corrosionintergranular corrosion occurs,occurs, and aand a partial disintegrationpartial disintegration of metal may resultof metal may result withwith general weakening of structuregeneral weakening of structure.. www.indiandentalacademy.comwww.indiandentalacademy.com
  156. 156. STABILIZATION:STABILIZATION: By addingBy adding TitaniumTitanium ((approximately 6 times ofapproximately 6 times of carboncarbon)) precipitationprecipitation ofof chromium carbide can bechromium carbide can be inhibitedinhibited for a short period at temperaturesfor a short period at temperatures ordinarily encountered in soldering procedures.ordinarily encountered in soldering procedures. www.indiandentalacademy.comwww.indiandentalacademy.com
  157. 157. Soldering for stainless steel:Soldering for stainless steel: Silver soldersSilver solders are used as theirare used as their solderingsoldering temperaturetemperature isis lowlow. These are alloys of. These are alloys of Ag, Cu,Ag, Cu, andand ZnZn to whichto which SnSn,, InIn may be added tomay be added to lowerlower fusion temperaturefusion temperature andand improve solderimprove solder abilityability.. www.indiandentalacademy.comwww.indiandentalacademy.com
  158. 158. COBALT-CHROMIUM-NICKEl ALLOYS:COBALT-CHROMIUM-NICKEl ALLOYS: Co-Cr-Ni alloys are used successfully in orthodonticCo-Cr-Ni alloys are used successfully in orthodontic appliances.appliances. These alloys were originally developed for use asThese alloys were originally developed for use as watch springs (Elgiloy).watch springs (Elgiloy). COMPOSITION:COMPOSITION: AA representative composition by massrepresentative composition by mass is Co-40%,is Co-40%, Cr-20%, Ni-15%, Mo-70%, Mn-2%, C-0.16%,Cr-20%, Ni-15%, Mo-70%, Mn-2%, C-0.16%, Be-0.04%, Fe-15. 8%.Be-0.04%, Fe-15. 8%. www.indiandentalacademy.comwww.indiandentalacademy.com
  159. 159. PROPERTIES:PROPERTIES:  Excellent resistanceExcellent resistance to tarnish & corrosion.to tarnish & corrosion.  Yield strength, hardness, tensile strength areYield strength, hardness, tensile strength are approximatelyapproximately equal to 18-8 stainless steelequal to 18-8 stainless steel..  Ductility is greaterDuctility is greater than 18-8 stainless steel.than 18-8 stainless steel.  More responsiveMore responsive to low temperature heatto low temperature heat treatment.treatment. www.indiandentalacademy.comwww.indiandentalacademy.com
  160. 160. NICKEL-TITANIUM ALLOYSNICKEL-TITANIUM ALLOYS  Called asCalled as NITINOLNITINOL  It has aIt has a large working range because of lowlarge working range because of low stiffnessstiffness in combinationin combination with moderately highwith moderately high strength.strength. www.indiandentalacademy.comwww.indiandentalacademy.com
  161. 161. COMPOSITIONCOMPOSITION  Ni-Ti alloysNi-Ti alloys used inused in dentistrydentistry containcontain approximately 54% Ni, 44% Ti and 2% or lessapproximately 54% Ni, 44% Ti and 2% or less cobalt.cobalt.  This alloy can exist in variousThis alloy can exist in various crystallographiccrystallographic formsforms. At. At high temperatureshigh temperatures, a BCC lattice, a BCC lattice austentite phase occurs, onaustentite phase occurs, on coolingcooling a CHa CH Martensitic phase occurs.Martensitic phase occurs. www.indiandentalacademy.comwww.indiandentalacademy.com
  162. 162. These characteristics of the austentite toThese characteristics of the austentite to martensite phase transition results inmartensite phase transition results in two uniquetwo unique featuresfeatures ofof potential clinical relevancepotential clinical relevance ::  Shape memoryShape memory andand Super elasticitySuper elasticity.. Memory effect is achieved by first establishing aMemory effect is achieved by first establishing a shape at temperatures nearshape at temperatures near 482°C482°C.. www.indiandentalacademy.comwww.indiandentalacademy.com
  163. 163.  If the appliance such as an orthodontic arch wire, isIf the appliance such as an orthodontic arch wire, is then cooled and formed into a second shape andthen cooled and formed into a second shape and heated through a lower transition temperature, theheated through a lower transition temperature, the wire will return into its original shape.wire will return into its original shape.  Inducing the austentite to martensite transition byInducing the austentite to martensite transition by stress can produce super elasticity, a phenomenonstress can produce super elasticity, a phenomenon that is employed with some nickel-titaniumthat is employed with some nickel-titanium orthodontic wires and some endodontic files.orthodontic wires and some endodontic files. www.indiandentalacademy.comwww.indiandentalacademy.com
  164. 164. ββ-Titanium alloys-Titanium alloys Like stainless steel and Nitinol,Like stainless steel and Nitinol, pure titanium haspure titanium has different crystallographic formsdifferent crystallographic forms at high and lowat high and low temperatures.temperatures. AtAt temperatures lower than 885° Ctemperatures lower than 885° C, the hexagonal, the hexagonal close-packed (HCP) or α-crystal lattice is stable,close-packed (HCP) or α-crystal lattice is stable, where as atwhere as at higher temperaturehigher temperature, the metal re-, the metal re- arranges into a BCC or β-crystal lattice.arranges into a BCC or β-crystal lattice. An alloy with the composition ofAn alloy with the composition of TitaniumTitanium-11%,-11%, molybdenum-6%, Zirconium-4%, tin is producedmolybdenum-6%, Zirconium-4%, tin is produced inin wrought wire formwrought wire form forfor orthodontic applicationsorthodontic applications..www.indiandentalacademy.comwww.indiandentalacademy.com
  165. 165. Properties:Properties: 1)1) Low elastic modulus.Low elastic modulus. 2)2) High ratio of yield strength to elastic modulusHigh ratio of yield strength to elastic modulus produces orthodontic appliances that can sustainproduces orthodontic appliances that can sustain large elastic activations.large elastic activations. 3)3) Highly cold worked.Highly cold worked. 4)4) Excellent corrosion resistance and environmentalExcellent corrosion resistance and environmental stability.stability. www.indiandentalacademy.comwww.indiandentalacademy.com
  166. 166. GOLD ALLOYS :GOLD ALLOYS : Gold wires areGold wires are occasionally employedoccasionally employed in thein the construction ofconstruction of removable partial denture claspsremovable partial denture clasps butbut usedused inin fabricating orthodontic appliancesfabricating orthodontic appliances, and, and asas retention pins for restorations.retention pins for restorations. www.indiandentalacademy.comwww.indiandentalacademy.com
  167. 167. COMPOSITION:COMPOSITION:  Many gold wires resemble the type IV gold castingMany gold wires resemble the type IV gold casting alloys in composition, but typically they containalloys in composition, but typically they contain less gold.less gold.  Two types of gold wiresTwo types of gold wires are recognized in ADA.are recognized in ADA. Specification No.7 (1984).Specification No.7 (1984). Type IType I-High noble or noble metal alloys, they must-High noble or noble metal alloys, they must contain atcontain at least 75%least 75% of gold and platinum groupof gold and platinum group metals.metals. Type IIType II-High noble or noble metal alloys, that must-High noble or noble metal alloys, that must contain atcontain at least 65%least 65% of some noble metals.of some noble metals. www.indiandentalacademy.comwww.indiandentalacademy.com
  168. 168. GENERAL EFFECTS OF THE CONSTITUENTS:GENERAL EFFECTS OF THE CONSTITUENTS: Pt-PdPt-Pd ensureensure thatthat wire does not meltwire does not melt oror recrystallizerecrystallize during soldering procedures.during soldering procedures. EnsureEnsure aa fine grain structurefine grain structure.. CuCu -contributes to ability of alloy to age harden,-contributes to ability of alloy to age harden, NiNi - strengthener, reduces ductility.- strengthener, reduces ductility. ZnZn - scavenger.- scavenger. www.indiandentalacademy.comwww.indiandentalacademy.com
  169. 169. MECHANICAL PROPERTIES OF NOBLE ALLOYMECHANICAL PROPERTIES OF NOBLE ALLOY WIRESWIRES:: A wire of a given composition isA wire of a given composition is generally superiorgenerally superior in mechanical properties to a casting of the samein mechanical properties to a casting of the same composition.composition. www.indiandentalacademy.comwww.indiandentalacademy.com
  170. 170. Because:Because:  Casting containsCasting contains unavoidable porosityunavoidable porosity, which has, which has a weakening effect.a weakening effect.  When cast ingot is drawn into wire, the smallWhen cast ingot is drawn into wire, the small pores and surface projections may be collapsed,pores and surface projections may be collapsed, and welding may occur so that defects disappear.and welding may occur so that defects disappear. Any defects of this type that areAny defects of this type that are not eliminatednot eliminated willwill weakenweaken the wire.the wire.  Because ofBecause of Fibrous microstructureFibrous microstructure.. www.indiandentalacademy.comwww.indiandentalacademy.com
  171. 171. Silver- palladium alloys:  White in colorWhite in color  Predominantly silver in composition but havePredominantly silver in composition but have substantial mounts of palladium, that providesubstantial mounts of palladium, that provide nobility and promote the silver resistance.nobility and promote the silver resistance.  May or may not have copper and a small amount ofMay or may not have copper and a small amount of gold.gold. DisadvantagesDisadvantages  Poor castabilityPoor castability  Greater potential for tarnish and corrosion.Greater potential for tarnish and corrosion. www.indiandentalacademy.comwww.indiandentalacademy.com
  172. 172. DENTAL IMPLANT MATERIALS:DENTAL IMPLANT MATERIALS: Most commonly,Most commonly, metalsmetals andand alloysalloys are used.are used. InitiallyInitially surgical grade stainless steelsurgical grade stainless steel andand Co-CrCo-Cr alloysalloys were used because of theirwere used because of their acceptableacceptable physical propertiesphysical properties and relativelyand relatively good corrosiongood corrosion resistanceresistance andand biocompatibilitybiocompatibility.. www.indiandentalacademy.comwww.indiandentalacademy.com
  173. 173. STAINLESS STEEL: (S-S)STAINLESS STEEL: (S-S)  Surgical stainless steel is an iron-carbon (0.05%)Surgical stainless steel is an iron-carbon (0.05%) alloy with approximatelyalloy with approximately 18% chromium18% chromium to impartto impart corrosion resistance andcorrosion resistance and 8% nickel8% nickel to stabilize theto stabilize the austentite structure.austentite structure.  The alloy is most frequentlyThe alloy is most frequently usedused in ain a wroughtwrought andand heat-treated conditionheat-treated condition..  It hasIt has increased strengthincreased strength andand ductilityductility; thus it is; thus it is resistant to fractureresistant to fracture..www.indiandentalacademy.comwww.indiandentalacademy.com
  174. 174. Co-Cr-Mo alloyCo-Cr-Mo alloy  These are most often used in aThese are most often used in a castcast oror cast andcast and annealed conditionannealed condition..  CompositionComposition 63% of Co, 30% of Cr, 5% Mo63% of Co, 30% of Cr, 5% Mo and small concentrations of C, Mn, Ni.and small concentrations of C, Mn, Ni.  MolybdenumMolybdenum serves toserves to stabilizestabilize the structure, andthe structure, and carboncarbon asas hardenerhardener..  These haveThese have outstanding resistance to corrosionoutstanding resistance to corrosion..  These areThese are least ductileleast ductile..www.indiandentalacademy.comwww.indiandentalacademy.com
  175. 175. TITANIUMTITANIUM ANDAND Ti-Al-V ALLOYTi-Al-V ALLOY www.indiandentalacademy.comwww.indiandentalacademy.com
  176. 176. www.indiandentalacademy.comwww.indiandentalacademy.com
  177. 177. Commercially pure Ti (CPTi) has become one ofCommercially pure Ti (CPTi) has become one of thethe material of choicematerial of choice because of its predictablebecause of its predictable interaction with the biological environment.interaction with the biological environment. Titanium is aTitanium is a highly reactive materialhighly reactive material, it oxidizes, it oxidizes on contact with air or normal tissue fluids. Thison contact with air or normal tissue fluids. This reactivity is favourable for implant devicesreactivity is favourable for implant devices because itbecause it minimizes biocorrosionminimizes biocorrosion.. AnAn oxide layeroxide layer 1010 A°A° thick forms on the cutthick forms on the cut surface of pure Ti within a millisecond. Thus, anysurface of pure Ti within a millisecond. Thus, any scratch or nick in the oxide coating is essentiallyscratch or nick in the oxide coating is essentially self healingself healing.. www.indiandentalacademy.comwww.indiandentalacademy.com
  178. 178. Composition of alloyed TiComposition of alloyed Ti TiTi - 90wt%- 90wt% AlAl- 6wt%- 6wt% VaVa- 4wt%- 4wt% www.indiandentalacademy.comwww.indiandentalacademy.com
  179. 179. Properties:Properties:  HighHigh strength : weight ratio.strength : weight ratio.  Modulus of elasticityModulus of elasticity approximatelyapproximately one halfone half ofof that of stainless steel or Cr-Co alloys.that of stainless steel or Cr-Co alloys.  Few titanium substructures areFew titanium substructures are plasma-sprayedplasma-sprayed oror coatedcoated with awith a thin layer of calcium phosphatethin layer of calcium phosphate ceramicceramic.. www.indiandentalacademy.comwww.indiandentalacademy.com
  180. 180. TheThe rationalerationale for coating the implant with tricalciumfor coating the implant with tricalcium phosphate or hydroxyapatite, both rich in calciumphosphate or hydroxyapatite, both rich in calcium and phosphorus isand phosphorus is to produce a bioactive surfaceto produce a bioactive surface thatthat promotes bone growthpromotes bone growth andand induces a directinduces a direct bond between the implant and hard tissuebond between the implant and hard tissue.. TheThe rationalerationale forfor plasma sprayedplasma sprayed surface is tosurface is to provide a roughenedprovide a roughened,, biologically acceptablebiologically acceptable surfacesurface forfor bone ingrowthbone ingrowth toto ensure anchorageensure anchorage inin the jaw.the jaw. www.indiandentalacademy.comwww.indiandentalacademy.com
  181. 181. OTHER METALS:OTHER METALS: Gold, Palladium, Tantalum, Platinum and alloys ofGold, Palladium, Tantalum, Platinum and alloys of these metals.these metals. RecentlyRecently ZirconiumZirconium,, TungstenTungsten are used.are used. www.indiandentalacademy.comwww.indiandentalacademy.com
  182. 182. BIOCOMPATABILITY OF METALS:BIOCOMPATABILITY OF METALS: Laboratory techniques performed with metalsLaboratory techniques performed with metals maymay exposeexpose us occasionally or routinely tous occasionally or routinely to excessively high concentrations ofexcessively high concentrations of BerylliumBeryllium andand Nickel dustNickel dust andand Beryllium vapour.Beryllium vapour. www.indiandentalacademy.comwww.indiandentalacademy.com
  183. 183. BERYLLIUMBERYLLIUM Although the beryllium concentration in dentalAlthough the beryllium concentration in dental alloys rarely exceedsalloys rarely exceeds 2 wt %2 wt % the amount ofthe amount of berylliumberyllium vaporvapor released in to the breathing spacereleased in to the breathing space during melting of Ni-Cr-Be alloys may beduring melting of Ni-Cr-Be alloys may be significantsignificant over an extended period.over an extended period. www.indiandentalacademy.comwww.indiandentalacademy.com
  184. 184. The risk of Beryllium vapour exposure isThe risk of Beryllium vapour exposure is greatest forgreatest for dental techniciansdental technicians during alloyduring alloy melting especially in themelting especially in the absenceabsence of an adequateof an adequate exhaustexhaust andand filtration system.filtration system. High levels of Beryllium have been measuredHigh levels of Beryllium have been measured duringduring finishingfinishing andand polishingpolishing when a localwhen a local exhaust system was not used. They wereexhaust system was not used. They were reducedreduced to levels considered safe whento levels considered safe when exhaust fanexhaust fan waswas used.used. www.indiandentalacademy.comwww.indiandentalacademy.com
  185. 185. Exposure of beryllium may result in acute andExposure of beryllium may result in acute and chronic forms of Beryllium diseasechronic forms of Beryllium disease BERYLLIOSIS.BERYLLIOSIS. CLINICAL FEATURESCLINICAL FEATURES:: SymptomsSymptoms range from coughing, chest pain andrange from coughing, chest pain and general weakness to pulmonary dysfunction.general weakness to pulmonary dysfunction. Contact dermatitisContact dermatitis Chemical pneumonitisChemical pneumonitis www.indiandentalacademy.comwww.indiandentalacademy.com
  186. 186. NICKEL:NICKEL: It is a great concern to dental patients with aIt is a great concern to dental patients with a knownknown allergyallergy to this element.to this element. The cloud ofThe cloud of controversycontroversy continues to hangcontinues to hang over the use of nickel in Dentistry.over the use of nickel in Dentistry. DermatitisDermatitis resulting from contact with nickelresulting from contact with nickel solutions was described as early assolutions was described as early as 19891989.. www.indiandentalacademy.comwww.indiandentalacademy.com
  187. 187. Inhalation, ingestion and dermal contactInhalation, ingestion and dermal contact ofof nickel or nickel containing alloys arenickel or nickel containing alloys are common because nickel is found incommon because nickel is found in environmental sourcesenvironmental sources such as air, soil andsuch as air, soil and food as well as in synthetic objects such asfood as well as in synthetic objects such as coins, kitchen utensils, and jewelry.coins, kitchen utensils, and jewelry. www.indiandentalacademy.comwww.indiandentalacademy.com
  188. 188. Nickel allergy was determined byNickel allergy was determined by PATCH TESTPATCH TEST ((Luis-Blanco- Dalmau JPD 1982: 48; 99-101Luis-Blanco- Dalmau JPD 1982: 48; 99-101)) described a standard patch test consisting ofdescribed a standard patch test consisting of 5%5% Nickel sulfate solution or 5% Nickel sulfateNickel sulfate solution or 5% Nickel sulfate solution on a petrolatum basesolution on a petrolatum base, in centre portion, in centre portion of a square Band-Aid of good quality.of a square Band-Aid of good quality. www.indiandentalacademy.comwww.indiandentalacademy.com
  189. 189. Band-Aids in positionBand-Aids in position One Band-Aid is removed. Observe for ++One Band-Aid is removed. Observe for ++ Both the Band-Aids are removed for comparisonBoth the Band-Aids are removed for comparison Magnified erythema,papules,and vesicles,+++Magnified erythema,papules,and vesicles,+++ www.indiandentalacademy.comwww.indiandentalacademy.com
  190. 190. The patch is applied onThe patch is applied on medial aspect of upper armmedial aspect of upper arm,, which was cleaned with awhich was cleaned with a alcohol swabalcohol swab, this is left, this is left in place forin place for 48 hrs undisturbed48 hrs undisturbed. The patient is. The patient is instructed not to moisten the arm or remove theinstructed not to moisten the arm or remove the patch during this time. A Band-Aidpatch during this time. A Band-Aid without anywithout any reagentreagent is placed adjacent to the first acts ais placed adjacent to the first acts a controlcontrol.. After 48 hrs, the control Band-aid is removed. TheAfter 48 hrs, the control Band-aid is removed. The second Band-Aid is removed and the skin issecond Band-Aid is removed and the skin is cleaned usingcleaned using alcoholalcohol oror acetoneacetone,, tests are readtests are read after 20 min.after 20 min. www.indiandentalacademy.comwww.indiandentalacademy.com
  191. 191. SSigns for recording degrees of patch test reactions are :igns for recording degrees of patch test reactions are : 00 No reaction.No reaction. ++ Erythema.Erythema. ++++  Erythema, papules.Erythema, papules. ++++++ Erythema, papules, vesicles.Erythema, papules, vesicles. ++++++++  Marked edema with vesicles.Marked edema with vesicles. www.indiandentalacademy.comwww.indiandentalacademy.com
  192. 192.  DIMETHYL GLYOXINE TESTDIMETHYL GLYOXINE TEST::  FEIGLFEIGL andand SHORESHORE stated that few drops ofstated that few drops of 1%1% alcohol solution of dimethyl glyoxime, few dropsalcohol solution of dimethyl glyoxime, few drops of ammonium hydroxideof ammonium hydroxide added to a metallicadded to a metallic object, skin on solution will produce aobject, skin on solution will produce a strawberrystrawberry red insoluble saltred insoluble salt in presence of nickel.in presence of nickel. www.indiandentalacademy.comwww.indiandentalacademy.com

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