metallurgical properties of casting materials

METALLURGICAL PROPERTIES OF

CASTING MATERIALS

DEEPA JINAN

BAPJI DENTAL COLLEGE & HOSPITAL

CONTENTS• Introduction• General characteristics of metals• Casting materials & alloys

DefinitionClassification of casting materialsDesirable properties

• Components of alloysNoble metalsBase metals

• Solidification & crystallization of metals & Alloys• Phase diagrams & dental alloys• Types Of alloys & significance

• General characteristics of metals• Structure & properties of metals• Structure & properties of alloys• Classification of metals & alloy systems• Dental casting alloys

CONTENTS

• Effects of mechanical treatment• Effects of heat treatment• Alloy strengthening mechanisms• Mechanism for corrosion resistance• Casting gold alloys• Metal ceramic alloys• Base metal alloys• Titanium alloys• Comparison between noble metal & base metal

alloys• References

INTRODUCTION

Metallurgy

Mosby’s dental dictionary. Definition of metallurgy. Restorative Dental Materials. 11th Ed. Missouri:elsivier; 2004. p3904Craig R G, Powers J M. Nature of Metals and Alloys. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002. p164-180.

Physical and chemical behavior of metals & alloys • Bulk • Atomic levelEffect of mechanical treatment

Effect of heat treatment

Study of metals and alloys

The study of metals and their properties, including

separating metals from their ores, the making and

compounding of alloys, and the technology and science of working and heat treating metals to alter their physical

charachteristics.

INTRODUCTION Metals & alloys

Anusavice K J. Solidification and Microstructure of metals. Philips Science of dental materials. 11th ed. Missouri: Elsevier; 2003p.103-117Craig R G, Powers J M. Nature of Metals and Alloys. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002. p164-180.

CASTING ALLOYS

FINAL STRUCTURE

FURTHER MANIPULATED

WROUGHT ALLOY

INTRODUCTION Significance of Metallurgy in dentistry

Craig R G, Powers J M. Nature of Metals and Alloys. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002. p164-180.

Diverse metals & alloys – characteristic behavior

Properties of metals - guide in fabrication of cast structures

COMPOSITION OF CASTING MATERIAL

CLINICAL USE & ENVIRONMENT

BUR HARDNESS IMPORTANT

CORROSION RESISTANCE

LESS IMPORTANT

CROWNBIOCOMPATIBILIT

YCORROSION RESISTANCE

Properties

• Lustre• Opacity• Density• High boiling points & melting points• Solids at room temperature• Thermal conductivity• Electrical conductivity• Ductility & malleability

Anusavice K J. Solidification and Microstructure of metals. Philips Science of dental materials. 11th ed. Missouri: Elsevier; 2003p.103-117

GENERAL CHARACTERISTICS OF METALS

GENERAL CHARACTERISTICS OF METALSProperties - valence Elelectron configurationMetallic bondResults from ↑spatial extension of valence e- when an aggregate of metal atoms is brought close together.

+ve charged

ionic core

+ve charged

ionic core

+ve charged

ionic core

+ve charged

ionic core

+ve charged

ionic core

+ve charged

ionic core

Unbound / free valance e- forms cloud or gas

equilibrium between electrostatic force s results in inter atomic space

• The term alloy system refers to all possible compositions of an alloy

0% 100%

0%100%

SILVER

COPPER

CASTING ALLOYSDEFINITION• A substance with metallic properties that is

composed of two or more chemical elements, at least one of which is a metal

CLASSIFICATION OF CASTING ALLOYS

BASED ON NOBILITY

HIGH NOBLE ALLOYS

PREDOMINANTLY BASE METAL ALLOYS

NOBLE ALLOYS

Contains > 40 wt% Au and > 60 wt% of the noble metal elements (Au + Ir + Os + Pd + Pt + Rh + Ru)

Contains > 25 wt % of the noble metal elements

Contains < 25 wt % of the noble metal elements

Gladwin M, Bagby M. Materials for fixed indirect Restorations and Prostheses. Clinical aspects of dental materials. China: Lippincott Williams & Wilkins. 2009. p 131-145.

Revised ADA Classification, 2003

HIGH NOBLE ALLOYS

PREDOMINANTLY BASE METAL ALLOYS

NOBLE ALLOYS

Contains > 40 wt% Au and > 60 wt% of the noble metal elements (Au + Ir + Os + Pd + Pt + Rh + Ru)

Contains > 25 wt % of the noble metal elements

Contains < 25 wt % of the noble metal elements

TITANIUM & TITANIUM ALLOYS

Titanium ≥ 85 wt%

BASED ON USE

CROWN & BRIDGE ALLOYS

RPD ALLOYS

METAL CERAMIC ALLOYS

Gladwin M, Bagby M. Materials for fixed indirect Restorations and Prostheses. Clinical aspects of dental materials. China: Lippincott Williams & Wilkins. 2009. p 131-145.

CASTING MATERIALS

DESIRABLE PROPERTIES

PURE ELEMENTS

ALLOYS

COMBINED

Biocompatibility Ease of melting Ease of casting Ease of polishing Little solidification

shrinkage Minimal reactivity with the

mold material Good wear resistance High strength Excellent corrosion

resistance Porcelain Bonding

NOBLE METALS

Soft and ductile

A yellow “Gold” hue

• Density of 19.3 gms/cm3

• Melting point of 1063°C,

• Boiling point of 2970 °C

• CTE of 14.2×10-6/°C

Craig R G, Powers J M. Noble dental alloys and solders. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002. p449-472

Excellent corrosion resistance

NOBLE METALS

PLATINUM

Bluish white metal- tough ductile & malleable

Increases strength and corrosion resistance

It helps to reduce the grain size

• Melting point of 1769°C

• CTE 8.9×10-6/°C

NOBLE METALS

PALLADIUM

Hardens as well as whitens the alloy

Raises the fusion temperaturetemperature & provides tarnish

resistance

Absorbs large quantities of H₂ when heated

• CTE 11.8×10-6/°C

NOBLE METALSIRIDIUM & RUTHENIUM

Added in very small quantities about 100 to 150 ppm

Help to decrease the grain size

BASE METALS

CHROMIUM,COBALT, NICKEL, IRON, COPPER,

Reactive with environment

Invaluable components of dental casting alloys

Influences on physical properties

Strengthening effect

McCabe J F, Walls A W G. Base metal casting alloys. Applied dental materials. 9th ed. Hong kong; Blackwell Publishing Ltd: 2008. p,71-79

BASE METALS

SILVER

Malleable, ductile white metal

Increases strength and hardness

In large amounts, it reduces tarnish resistance- combines

with S,Cl₂, P

• Density 10.4gms/cm3

• CTE is 19.7 ×10-6/°C

NOBLE METALS

COBALT

Imparts hardness, strength and rigidity

• CTE 13.8×10-6/°C

NOBLE METALS

NICKEL

Decreases

• Strength• Hardness

• Modulus of elasticity • Fusion temperature

• CTE 13.3×10-6/°C

Increases ductility

BASE METALS

Smith E A. A Manual on dental metallurgy and non-metallic Materials 6th Ed. London:J & A Churchill Ltd;1947.p3-4

CHROMIUM

Passivating effect – corrosion resistance

• CTE 6.2×10-6/°C

Increases the melting point & content not to exceed 30 %

Acts in solid solution hardening & Precipitation hardening

BASE METALS

COPPER

Principal hardener

• CTE 16.5×10-6/°C

Reduces the density of gold alloys

Reduces resistance to tarnish and corrosion of gold alloymaximum content NOT to

exceed 16%.

BASE METALS

Scavenger for oxygen

MELTING SILVER ALLOY WITHOUT ZINC

SOLIDIFICATION OF SILVER ALLOY WITHOUT ZINC

POROSITIES

BASE METALS

GALLIUM

Grayish metal

• Melting point of 29.8°C

Oxides are important to bonding of ceramic to metal

NOBLE METALS

Soft and ductile

A yellow “Gold” hue

• CTE of 14.2×10-6/°C

Excellent corrosion resistance

SOLIDIFICATION & CRYSTALIZATION OF METALS

SOLIDIFICATION

FREEZING POINT OR SOLIDIFICATION

TEMPERATURE OF PURE METALFUSION TEMPERATURE

SUPERCOOLING

B’-B – CRYSTALIZATION BEGINS FOR PURE

METALS

RELEASE OF THE LATENT HEAT OF FUSION CAUSES THE

TEMPERATURE TO RISE TO TF

LIQUID – HIGH ENERGY STATE

SOLID – LOW ENERGY STATE

CRYSTALIZATION COMPLETE

SOLIDIFICATION

FREEZING POINT OR SOLIDIFICATION

TEMPERATURE OF PURE METALFUSION TEMPERATURE

SUPERCOOLING

B’-B – CRYSTALIZATION BEGINS FOR PURE

METALS

RELEASE OF THE LATENT HEAT OF FUSION CAUSES THE

TEMPERATURE TO RISE TO TF

LIQUID – HIGH ENERGY STATE

SOLID – LOW ENERGY STATE

CRYSTALIZATION COMPLETE

SOLIDIFICATION & CRYSTALIZATION OF ALLOYS

NUCLEI

MOLTEN ALLOY

COOLING

NucleationIr

GRAIN REFINERSHigh MP

For even Nucleation

COOLING

GRAINS

Grow into

ENLARGE GRAIN BOUNDARIES

DENDRITES

SOLIDIFICATION & CRYSTALIZATION OF ALLOYS

GRAIN SIZE

COOLING RATE

ALLOY COMPOSITION

PRESENCE OF GRAIN REFINERS

ALLOY STRENGTH

WORKABILITY

SUCEPTIBILITY TO CORROSION

Affects

Depends onFaster cooling rate

Noble metals

Ir, Ru,

SMALL GRAINED

SOLIDIFICATION & CRYSTALIZATION OF ALLOYSSIGNIFICANCE

Typically solidify with a dendritic micro-structure

Solidify with an Equiaxed polycrystalline microstructure

Equiaxed – grains uniform in size & shape

BASE METAL CASTING ALLOYS

NOBLE METAL CASTING ALLOYS

Fine grainedLarge grained

SMALLER THE GRAIN SIZE

MORE DUCTILE AND STRONGER

PRODUCES A MORE

HOMOGENOUS CASTING

IMPROVES THE TARNISH

RESISTANCE

elongated morphology of dendrites

PHASE DIAGRAMS & DENTAL ALLOYS

PHASE A state of matter distinct from matter around it

ICE WATER

ARRANGEMENT OF ATOMS

SINGLE PHASEHomogenous composition

MULTI-PHASEAreas with different

composition

BINARY PHASE DIAGRAMS TERTIARY PHASE DIAGRAMS

EQUILIBRIUM PHASE DIAGRAM FOR ALLOYS

Anusavice K J. Equilibrium phases in cast alloys. Philips Science of dental materials. 11th ed. Missouri: Elsevier; 2003p.119-141

COOLING CURVE EXPERIMENTS PERFORMED ON A SERIES OF ALLOYS FROM THE A-B SYSTEM

ISOTHERMAL FREEZING

NO SINGLE FREEZING TEMPERATURESOLIDIFY OVER A RANGE

COOLING CURVE EXPERIMENTS PERFORMED ON A SERIES OF ALLOYS FROM THE A-B SYSTEM

EQUILIBRIUM PHASE DIAGRAM

LIQUIDUS TEMPERATURE – FIRST

SOLID FORMS

SOLIDUS TEMPERATURE – LAST

SOLID FORMS

LIQUIDUS

SOLIDUS

65% PALLADIUM & 35 %SILVER

COMPOSITION (65WT% Pd)

Alloy is in liquid state

DASHED LINE PO

POINT R

Temperature - 1400°c

77% Pd

POINT S

57% Pd - Y

71% Pd - W

POINT T

52% Pd - T

Anusavice K J. Equilibrium phases in cast alloys. Philips Science of dental materials. 11th ed. Missouri: Elsevier; 2003p.119-141

13701340

SIGNIFICANCE DISTANCE BETWEEN LIQUIDUS & SOLIDUS LINES

SMALL – Ag-Au SystemLARGE – Au-Pt System

Varies for Au-Cu Sytem

NARROW LIQUIDUS SOLIDUS RANGE

ALLOY IN LIQUID STATE FOR SHORTER

LESS SUCEPTIBLE TO OXIDATION &CONTAMINATION

Alloy remain partially molten for longer period

TEMPERATURE OF LIQUIDUS LINE

Ranges from 962-1064Ranges from 1064-1772

LIQUIDUS LINE AT LOWER TEMPERATURE

Heating easier Fewer side reactions

Shrinkage less problematic

ALLOYS

LIQUID METAL A LIQUID METAL BLIQUID ALLOY ABSOLID ALLOY AB

METALS MIXED IN MOLTEN STATE

OUTCOMES BASED ON SOLUBILITY OF METALS IN EACH OTHER

SOLID SOLUTION - soluble EUTECTIC – not soluble INTERMETALLIC COMPOUND – form specific compound

FOLLOWED BY COOLING

SOLID SOLUTIONSGOLD COPPER SYSTEM

Miscible – in any combination – Properties resemble metals forming alloy

Au atoms occupy some positions of FCC, Cu atoms occupy some other - random

At a certain composition, Au atoms occupy some positions of FCC, Cu atoms occupy some other – specific pattern- ordered solutions

HIGHER STRENGTH & HARDNESSLOWER DUCTILITY

Melting ranges – Lower :smooth transition between two melting points

HIGHER CORROSION RESISTANCE

Presence of atoms of unequal size – more difficult for atomic

planes to slide

Single phase – more homogenousPresence of different phases- interact

electrochemicallyCraig R G, Powers J M. Nature of Metals and Alloys. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002. p164-180.

SOLID SOLUTIONS

Anusavice K J. Equilibrium phases in cast alloys. Philips Science of dental materials. 11th ed. Missouri: Elsevier; 2003p.119-141.

FACTORS DETERMINING EXTENT OF SOLID SOLUBILITY OF METALS

ATOMIC SIZE SIZE DIFFER BY LESS THAN 15%

VALENCE METALS OF SAME VALENCE MORE LIKELY TO FORM SOLID SOULTIONS

CHEMICAL AFFINITYHIGH DEGREE OF CHEMICAL AFFINITY – INTERMETALLIC

COMPOUND

CRYSTAL STRUCTURE SAME TYPE OF CRYSTAL STRUCTURE

EUTECTIC ALLOYSSILVER COPPER SYSTEM

Solidus lower than pure Ag OR Cu779.4

28.1 % Cu 71.9 % Ag

ABEGD - solidus AED – liquidus

Meet at mid range

Pure eutectic - melting point

Eutectic composition

Ag-Cu System important in high copper dental

amalgam

INTERMETALLIC COMPOUNDSSILVER TIN SYSTEM

Two metals react to form a specific compound

Ag₃Sn important intermetallic compound in dental amalgam

Ag₃Sn Intermetallic compound in Ag-Sn System, seen at 26.8wt% of Sn

EFFECT OF MECHANICAL TREATMENT

COLD / WORK HARDENING

CAST INGOT SUBJECTED TO

ROLLING, SWAGING,

WIRE DRAWING

MECHANICAL DEFORMATION

WROUGHT STRUCTURE

CRYSTALLINE/DENDRITIC STRUCTURE

GRAINS BROKEN,

ENTANGLED, ELONGATED

FIBROUS STRUCTURE

SUPERIOR MECHANICAL PROPERTIES

EMBRITTLE ALLOYS – LESS DUCTILE

EFFECT OF HEAT TREATMENT

RECRYSTALLIZATION & GRAIN GROWTH

COLD WORKED METALS & ALLOYS HEATING / ANNEALING

FIBROUS STRUCTURE GRADUALLY LOST

GRAIN/CRYSTALLINE STRUCTURES REAPPEARS RECRYSTALLIZATION/

GRAIN GROWTHDEPENDS

TEMPERATURE & DURATION OF

HEATINGCraig R G, Powers J M. Nature of Metals and Alloys. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002. p164-180.

ALLOY STRENGTHENING MECHANISMS

Solid solutions

Precipitation hardening

Grain refiners

Cold working

HEATING ALLOYSSECOND PHASE

APPEARS IN BODY OF ALLOY

BLOCKS THE MOVEMENT OF DISLOCATIONS

STRENGTH & HARDNESS INCREASEDAu-Pt alloy Fe

FePt₃

MECHANISMS FOR CORROSION RESISTANCE

Polishing metal restorations

Passivation

Increasing noble metal content

Avoiding dissimilar metal restorations

THIN ADHERENT OXIDE

PREVENTS DIFFUSION OF O₂

Fe - C Cr

Stainless steel

GOLD ALLOYS

ADA SPECIFICATION No. 5

High Gold Alloys - >70% Type I Type II

Type III

Type IV

Low Gold Alloys - >10wt%, < 45-50%

White Gold Alloys- Silver palladium alloys

INLAY GOLD ALLOY

CROWN & BRIDGE ALLOY

CASTING GOLD ALLOYSTYPE I - SOFT

HIGHLY DUCTILE

BURNISHED EASILY

Areas of low occlusal stress designed for simple inlays such as used in class I, III & V cavities

PROPERTIES

Hardness VHN (50 – 90)Tensile Strength 276 MPa Yield Strength 180 MPa Linear Casting Shrinkage 1.56%

Elongation or ductility 18- 46%

COMPOSITION

Au Ag Cu Pt Pd Zn&Ga 83% 10% 6% - 0.5% balance

CASTING GOLD ALLOYSTYPE II- MEDIUM

DUCTILE

HIGHER YEILD STRENGTH

Inlay or onlay restorations subject to moderate stress, thick three quarter crowns, pontics and full crowns

PROPERTIES

Hardness VHN (90-120)Tensile Strength 345 MPa Yield Strength 300 MPa Linear Casting Shrinkage 1.37%

Elongation or ductility 10 - 40.5%

COMPOSITION

Au Ag Cu Pt Pd Zn&Ga 77% 14% 7% - 1% balance

HARDER

CASTING GOLD ALLOYS

TYPE III- HARD

NOT DUCTILE

AGE HARDENED

Inlays subject to high stress and for crown and bridge

PROPERTIES

Hardness VHN (120-150)Tensile Strength 360 MPa Yield Strength 331MPa Linear Casting Shrinkage 1.42 %

Elongation or ductility 5- 39.4 %

COMPOSITION

Au Ag Cu Pt Pd Zn&Ga 79% 11% 5% - 3.5% balanceCraig R G, Powers J M. Noble dental alloys and solders. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002.

p449-4724

CASTING GOLD ALLOYSTYPE IV- EXTRA HARD

NOT DUCTILE

AGE HARDENED

Very high stress, crowns and long span bridges

PROPERTIES

Hardness VHN (150-200)Tensile Strength 462 MPa Yield Strength 703 MPa Linear Casting Shrinkage 2.03 %

Elongation or ductility 3 - 17 %

COMPOSITION

Au Ag Cu Pt Pd Zn&Ga 56% 25% 14% - 4% balanceCraig R G, Powers J M. Noble dental alloys and solders. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002.

p449-4724

CASTING GOLD ALLOYS

HEAT TREATMENTS

SOFTENING HEAT TREATMENT

HEATING FOR 10 MINS AT 700 C THEN QUENCHING

AGE HARDENING HEAT TREATMENT

HEATING CASTING TO ABOVE 450°C AND THEN ALLOWING IT TO COOL SLOWLY UNTIL TEMP DROPPED TO 200ᵒC FOLLOWED BY QUENCHING

REQUIREMENTS

They should be able to bond with porcelain.

Coefficient of thermal expansion

Its melting temperature should be higher than the porcelain firing temperature. It should be able to resist creep or sag.

It should not stain or discolor porcelain.

Oldest metal ceramic alloys

Composition:Gold – 75% to 88%Palladium – Upto 11%Platinum – Upto 8%Silver – 5%Trace elements like Indium, Iron and Tin for porcelain bonding

Gold-Platinum -Palladium

Biocompatibility Ease of melting Ease of casting Ease of polishing Sag reistance COTE Good wear resistance Hardness Resistance to discolouration Porcelain Bonding Economical

Composition:Gold – 39% to 53%Silver – 12% to 22%Palladium – 25% to 35%

trace amount of oxidizable elements are added for porcelain bonding

Gold-Palladium-Silver Biocompatibility

Ease of melting Ease of casting Ease of polishing Sag resistance COTE Good wear resistance Hardness Resistance to discoloration Porcelain Bonding Economical

Composition:Palladium – 55% to 60% Silver – 25% to 30% Indium and Tin

Palladium – 50% to 55% Silver – 35% to 40% Tin (Little or no Indium

Palladium-Silver Biocompatibility

Ease of melting Ease of casting Ease of polishing Sag resistance Thermal compatibility Good wear resistance Hardness Resistance to discoloration Porcelain Bonding Economical

Composition:

Palladium – 78% to 88% Cobalt – 4% to 10%

Palladium-Cobalt alloy Biocompatibility

Ease of melting Ease of casting Ease of polishing Sag resistance Thermal compatibility Good wear resistance Hardness Resistance to discoloration Porcelain Bonding Economical

CASTING MATERIALS

CONTENTS

• Base metal alloys• Titanium alloys• Comparison between noble metal & base metal

alloys• References

NOBLE METALS

BASE METALS

SOLIDIFICATION

TYPES OF ALLOYS

SOLID SOLUTIONS

EUTECTIC

INTERMETALLIC COMPOUNDS

TYPES OF ALLOYS

GOLD ALLOYS

BASE METAL ALLOYS

Nickel-chromium

Be FREE ALLOYSBe CONTAINING

ALLOYS

Composition:

Nickel – 62% to 77% Chromium – 11% to 22%Boron ,iron, molybdenum, Niobium or columbium and tantalum (trace elements).

Composition:

Nickel – 62% to 82% Chromium – 11% to 20%Beryllium – 2.0%aluminum, carbon, gallium, iron, manganese, molybdenum, silicon, titanium and /or vanadium are present.

ECONOMICALALLERGIC

POTENTIAL

CAN BE ETCHED

CASTING IS EASIER

BASE METAL ALLOYS

Composition:

Cobalt - 55 to 65%Chromium - 23 to 30%Nickel - 0 to 20%Molybdenum - 0 to 7%Iron - 0 to 5%Carbon - upto 0.4%Tungsten, Manganese, Silicon and Platinum in traces.

COBALT CHROMIUM ALLOY

HIGH STRENGTH

EXCELLENT CORROSION RESISTANCE

POOR BURNISHABILITY

BASE METAL ALLOYS

TITANIUM ALLOYS

Properties of titanium:

• Relatively light weight• Low density (4.5 g/cm3)• High strength (yield strength = 170-480 MPa; • ultimate strength = 240-550 MPa)• Passivity• Low coefficient of thermal expansion (8.5 x 10–6/°C)• Melting & boiling point of 1668°C & 3260°C

“MATERIAL OF CHOICE” IN DENTISTRY

OXIDE FORMATION PROPERTY

BIOCOMPATIBILITY

TITANIUM ALLOYS

Difficulties in casting Titanium :

-High melting point-High reactivity > 600°C – H, O, N-Difficulty in finishing-Difficulty in welding-Requires expensive equipments

LOW DENSITY DIFFICULT TO CAST IN CENTRIFUGAL CASTING

COMBINING CENTRIFUGAL,

VACUUM, PRESSURE, GRAVITY CASTING WITH ELECTRIC ARC MELTING

TECHNOLOGY

Marzouk MA. Cast restorations. 1st ed. India: All India publishers and distributers; 2001p.307-323.

NOBLE METAL ALLOYS

BASE METAL ALLOYS

DENSITY

MODULUS OF ELASTICITY ELONGATION

CASTING ENVIRONMENTTARNISH & CORROSION

ULTIMATE STRENGTH

RANGE OF MELTING TEMPERATURE

FINISHING & POLISHINGCASTABILITY-MOLDABILITY

SOLDERING

BIOCOMPATIBILITY

PORCELAIN BONDING

CASTING SGRINKAGE

NOBLE METAL ALLOYS

BASE METAL ALLOYS

DENSITY

HIGHEST DENSITY

LESS FORCE IN CENTRIFUGAL

CASTING

DENSITYALMOST HALF OF HIGH NOBLE

LOWER DENSITY ALLOWS MORE

RESTORATIONS PER UNIT WEIGHT &

LIGHTERACCELERATES FASTER – FORMS COMPLETE

CASTING MORE EASILY

VERY THIN CROSS SECTION DETAILS TO

BE AVOIDED

NOBLE METAL ALLOYS

BASE METAL ALLOYS

MELTING RANGE

LOWEST MELTING RANGE

CAST USING LOW HEAT TECHNIQUE

HIGHEST MELTING RANGE

GAS AIR FUEL

Ca SO₄ DIHYDRATE BONDED

INVESTMENTS

PHOSPHATE & SILICATE BONDED

INVESTMENTS

HIGH HEAT TECHNIQUEELECTRIC

RESISTANCE/INDUCTION MELTING

NOBLE METAL ALLOYS

BASE METAL ALLOYS

ULTIMATE STRENGTH

SUFFICIENT STRENGTH

FAILURE NOT CATASTROPHIC

DOUBLE TENSILE STRENGTH

SELDOM FAILS MECHANICALLY

NOBLE METAL ALLOYS

BASE METAL ALLOYS

ELONGATION

BURNISHABLE

EASIER TO ADJUST MARGINS IN CASE OF

DISCREPANCY

NOT BURNISHABLE

MARGINS TO BE PLACED IN

REACHABLE AND REPRODUCABLE

AREAS, CLASP ADJUSTMENT

DIFFICULT

NOBLE METAL ALLOYS

BASE METAL ALLOYS

MODULUS OF ELASTICITY

2-3 TIMES LESS THAN BASE METAL ALLOYS

ABRASION RESISTANCE LESS IN

COMPARISON

HIGH MODULUS OF ELASTICITY

GOOD ABRASION RESISTANCE

NOBLE METAL ALLOYS

BASE METAL ALLOYS

PORCELAIN BONDING

COMMONLY USED FOR FABRICATION OF

METAL CERAMIC RESTORATIONS

MOSTLY Ni Cr USED FOR METAL CERAMIC

McCabe J F, Walls A W G. Gold and Alloys of Noble metals, Applied dental materials. 9th ed. Hong kong; Blackwell Publishing Ltd: 2008. p62-70,McCabe J F, Walls A W G. Base metal casting alloys. Applied dental materials. 9th ed. Hong kong; Blackwell Publishing Ltd: 2008. p71-79

NOBLE METAL ALLOYS

BASE METAL ALLOYS

CASTING ENVIRONMEN

LESS SENSITIVE TO CASTING

ENVIRONMENT

ALLOY LESS SUCEPTIBLE TO CONTAMINANTS

MORE CONTROLLED & DEVOID OF

CONTAMINANTS

PALLADIUM – HIGH AFFINITY FOR

OXYGEN – POROSITY

CONTAMINANTS ( C,O₂) ADVERSELY CHANGE

PROPERTIES OF ALLOY

SILVER HAS HIGH AFFINITY FOR OXYGEN

– POROSITY & ROUGHNESS

NOBLE METAL ALLOYS

BASE METAL ALLOYS

CASTING SHRINKAGE

LESS SOLIDIFICATION SHRINKAGE

LESS TECHNIQUE SENSITIVE

HIGHER SOLIDIFICATION

SHRINKAGE

DIFFICULT TO PRODUCE RESTORATION WITH SATISFACTORY FIT

NOBLE METAL ALLOYS

BASE METAL ALLOYS

FINISHING & POLISHING

EASILY ACCOMPLISHED

LESS COMPLICATED ARMAMENTARIUM

MORE TIME TO ATTAIN BIOLOGIC SURFACES

REQUIRE HIGH SPEED EQUIPMENT

MORE ABRASIVE TOOLSELECTROLYTIC

POLISHING REQUIRED FOR Co Cr

NOBLE METAL ALLOYS

BASE METAL ALLOYS

SOLDERING

FAIRLY PREDICTABLE & EASY

GOLD SOLDERS FOR HIGH NOBLE. OR SILVER SOLDERS

TECHNIQUE SENSITIVE

REQUIRE INERT ENVIRONMENT

SPECIFIC SOLDER FOR EACH ALLOY

NOBLE METAL ALLOYS

BASE METAL ALLOYS

TARNISH & CORROSION

EXCELLENT RESISTANCE

NOBILITY

GOOD RESISTANCE

PASSIVITY

NOBLE METAL ALLOYS

BASE METAL ALLOYS

BIOCOMPATIBILITY

GENERALLY REGARDED AS HAVING GOOD

BIOCOMPATIBILITY

PALLADIUM ALLERGY

CONTAIN COMPONENTS

REGARDED AS TOXIC OR KNOWN ALLERGENS

Ni – KNOWN ALLERGENBe THOUGHT TO BE

CARCINOGENIC

CONCLUSION

NOBLE METAL ALLOYS SUPERIOR TO BASE METAL ALLOYS

COST IMPORTANT FACTOR

Marzouk MA. Cast restorations. 1st ed. India: All India publishers and distributers; 2001p.307-323

REFERENCES• Anusavice K J. Equilibrium phases in cast alloys. Philips Science of dental

materials. 11th ed. Missouri: Elsevier; 2003p.119-141.

• Anusavice K J. Solidification and Microstructure of metals. Philips Science of dental materials. 11th ed. Missouri: Elsevier; 2003p.103-117.

• Smith E A. A Manual on dental metallurgy and non-metallic Materials 6th Ed. London:J & A Churchill Ltd;1947.p3-4.

• Craig R G, Powers J M. Nature of Metals and Alloys. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002. p164-180.

• Craig R G, Powers J M. Noble dental alloys and solders. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002. p449-472.

• Craig R G, Powers J M. Cast and wrought base metal alloys. Restorative Dental Materials. 11th Ed. Missouri: Mosby; 2002. p449-472.

REFERENCES• Marzouk MA. Cast restorations. 1st ed. India: All India publishers and

distributers; 2001p.307-323.

• Marzouk MA. The biologic form and choice of materials for cast restorations. 1st ed. India: All India publishers and distributers; 2001p.341-344.

• Darvell BW. Metals I, Metal II, Casting alloys. 9th ed. New Delhi: Woodhead publishing INDIA Private limited; 2009. p 280-305, 306- 322, 435-449.

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