Dental casting alloys / dental implant courses

DENTAL CASTINGDENTAL CASTING
ALLOYSALLOYS
INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY
Leader in continuing Dental EducationLeader in continuing Dental Education
www.indiandentalacademy.comwww.indiandentalacademy.com

IntroductionIntroduction
Casting is one of the most widelyCasting is one of the most widely
used method for the fabrication ofused method for the fabrication of
metallic restoration outside the mouthmetallic restoration outside the mouth

History of Dental casting alloysHistory of Dental casting alloys
History isHistory is influencedinfluenced byby
• Technological changes of dental prosthesisTechnological changes of dental prosthesis
• Metallurgical advancementsMetallurgical advancements
• Price changes of precious metals since 1968Price changes of precious metals since 1968
Taggart presentation in 1907 was firstTaggart presentation in 1907 was first
Pure gold should be strengthened by additionPure gold should be strengthened by addition
of other metals such as Cu, Ag or Ptof other metals such as Cu, Ag or Pt

Indian Dental academyIndian Dental academy
Leader continuing dental educationLeader continuing dental education
Offer both online and offline dentalOffer both online and offline dental
coursescourses

InIn 19321932 National standard bureau roughlyNational standard bureau roughly
classified alloysclassified alloys
TypeType Au & Pt % VHNAu & Pt % VHN
I (soft) 83% 50 & 90I (soft) 83% 50 & 90
II (medium) 78% 90 & 120II (medium) 78% 90 & 120
III (hard) 78% 120 & 150III (hard) 78% 120 & 150
IV (Extra hard) 75% 150IV (Extra hard) 75% 150

 Tarnish tests indicated that alloys containingTarnish tests indicated that alloys containing
less than 65 – 75 % tarnished too readily forless than 65 – 75 % tarnished too readily for
dental usedental use
 Only Gold & Platinum were considered nobleOnly Gold & Platinum were considered noble
metalsmetals
 By 1948 the composition of noble metals wasBy 1948 the composition of noble metals was
diversediverse

Classification according toClassification according to 19481948
Type Au Ag Cu Pd PtType Au Ag Cu Pd Pt
ZnZn
A 79-92.5 3-12 2-4.5 0-0.5 0-0.5 0-0.5A 79-92.5 3-12 2-4.5 0-0.5 0-0.5 0-0.5
B 75-78% 12-14 7-10 1-4 0-1 0.5B 75-78% 12-14 7-10 1-4 0-1 0.5
C 62-78% 8-26 8-11 2-4 0-3 1C 62-78% 8-26 8-11 2-4 0-3 1
D 60-71.5 4.5-20 11-16 0-5 0-3.5 1-2D 60-71.5 4.5-20 11-16 0-5 0-3.5 1-2

 1950 there was a breakthrough when they1950 there was a breakthrough when they
successfully veneered a metal to porcelainsuccessfully veneered a metal to porcelain
 It was impossible to fuse gold & porcelainIt was impossible to fuse gold & porcelain
 Since 1930 Ni – Cr & Co – Cr have largelySince 1930 Ni – Cr & Co – Cr have largely
replaced type IV gold alloysreplaced type IV gold alloys
 After 1970 attention was diverted to otherAfter 1970 attention was diverted to other
metals when price of noble metals rose upmetals when price of noble metals rose up

Classification of Dental castingClassification of Dental casting
alloysalloys
Alloy types by functionAlloy types by function
Type I (soft) :Type I (soft) : easily burnished & Inlays subject toeasily burnished & Inlays subject to
slight stressslight stress
Type II (Medium) :Type II (Medium) : Inlays subjectInlays subject to moderateto moderate
stress thick three quarter crowns, abutments,stress thick three quarter crowns, abutments,
pontics & full crownspontics & full crowns
Type I & Type IIType I & Type II golds are often referred asgolds are often referred as
“Inlay“Inlay Golds”Golds”

Type III (Hard) :Type III (Hard) : Inlays subject to high stresses,Inlays subject to high stresses,
three quarter crowns, thin cast backings, abutments,three quarter crowns, thin cast backings, abutments,
pontics, full crowns, denture bases & short spanpontics, full crowns, denture bases & short span
fixed partial dentures. These can be age hardenedfixed partial dentures. These can be age hardened
Type IV (Extra Hard) :Type IV (Extra Hard) : Inlays subject to high stress,Inlays subject to high stress,
denture base bars, & clasps partial denture framedenture base bars, & clasps partial denture frame
works, long span fixed partial dentures can be ageworks, long span fixed partial dentures can be age
hardened by appropriate heat treatmenthardened by appropriate heat treatment
Type III & Type IVType III & Type IV are often referred asare often referred as “Crown &“Crown &
Bridge” alloysBridge” alloys

Metal Ceramic (Hard & Extra Hard)Metal Ceramic (Hard & Extra Hard)
• Suitable for veneering with dental porcelain,Suitable for veneering with dental porcelain,
copings, thin walled crowns, short span F.P.Dcopings, thin walled crowns, short span F.P.D
(Hard) long span F.P.D (Extra hard)(Hard) long span F.P.D (Extra hard)
• These alloys vary greatly in composition and mayThese alloys vary greatly in composition and may
be gold-, palladium-, nickel- or cobalt- basedbe gold-, palladium-, nickel- or cobalt- based
Removable Partial Denture AlloysRemovable Partial Denture Alloys
• It includes Ni- or Co- based alloys these haveIt includes Ni- or Co- based alloys these have
largely replaced Type IV gold alloys due tolargely replaced Type IV gold alloys due to
lighter weight, stronger and inexpensivelighter weight, stronger and inexpensive

Alloy types by DescriptionAlloy types by Description
1)1) Crown &Crown & Bridge alloysBridge alloys
 These include both gold & non – gold based, noble & baseThese include both gold & non – gold based, noble & base
metal alloysmetal alloys
 These encompass Type III & Type IV golds & ADAThese encompass Type III & Type IV golds & ADA
certified alloyscertified alloys
2)2) Silver – Palladium alloysSilver – Palladium alloys
 White colored & predominantly silverWhite colored & predominantly silver
 May or may not contain Cu & AuMay or may not contain Cu & Au
 Ag-Pd alloys have properties of Type III & Ag-Pd-CuAg-Pd alloys have properties of Type III & Ag-Pd-Cu
may have properties of Type IV goldsmay have properties of Type IV golds
 The major limitation is tarnish & corrosionThe major limitation is tarnish & corrosion

Metal Ceramic AlloysMetal Ceramic Alloys
Noble Metal AlloysNoble Metal Alloys
 Gold-Platinum-PalladiumGold-Platinum-Palladium
 Gold-Palladium-SilverGold-Palladium-Silver
 Gold- PalladiumGold- Palladium
 Palladium-SilverPalladium-Silver
 High PalladiumHigh Palladium
Base Metal AlloysBase Metal Alloys
 Nickel – ChromiumNickel – Chromium
 Cobalt - ChromiumCobalt - Chromium

Noble Metal Alloys for PorcelainNoble Metal Alloys for Porcelain
BondingBonding
Gold-Platinum-PalladiumGold-Platinum-Palladium
Contain Gold up to 88% with varying amounts of Pt,Contain Gold up to 88% with varying amounts of Pt,
Pd & small amounts of base metalsPd & small amounts of base metals
Gold-Palladium-SilverGold-Palladium-Silver
Contain 39 – 77 % Au, up to 35% Pd & Ag levels asContain 39 – 77 % Au, up to 35% Pd & Ag levels as
high as 22%high as 22%
Gold- PalladiumGold- Palladium
Au – 44 to 55% & 35 to 45% Pd these haveAu – 44 to 55% & 35 to 45% Pd these have
remained popular despite their high costremained popular despite their high cost

Palladium-SilverPalladium-Silver
Posses good high temperature strength, butPosses good high temperature strength, but
the higher levels of silver can causethe higher levels of silver can cause
discoloration (yellow, green or brown)discoloration (yellow, green or brown)
High PalladiumHigh Palladium
These are alloys with a palladium content upThese are alloys with a palladium content up
to 88%. One commercially successfulto 88%. One commercially successful
composition combined 79% Pd, 2% Au withcomposition combined 79% Pd, 2% Au with
small levels of either Copper or Cobaltsmall levels of either Copper or Cobalt

Base Metal Alloys for PorcelainBase Metal Alloys for Porcelain
BondingBonding
Nickel – ChromiumNickel – Chromium
Contains Ni up to 80% & Cr content 13 – 22% theContains Ni up to 80% & Cr content 13 – 22% the
properties & handling are improved by addition ofproperties & handling are improved by addition of
2% Beryllium2% Beryllium
Cobalt – ChromiumCobalt – Chromium
Contain 55–68% Co & 25-27% Cr but no BerylliumContain 55–68% Co & 25-27% Cr but no Beryllium
these alloys oxidize readily than Ni-Cr-Be group andthese alloys oxidize readily than Ni-Cr-Be group and
their longevity is yet to be establishedtheir longevity is yet to be established

Removable Partial Denture AlloysRemovable Partial Denture Alloys
Cobalt – ChromiumCobalt – Chromium
Contain 60% Co & 25-30% CrContain 60% Co & 25-30% Cr
Are used since 1930, Vitallium is the name commonlyAre used since 1930, Vitallium is the name commonly
associatedassociated
Nickel – ChromiumNickel – Chromium
Most often used due to relative ease of handling &Most often used due to relative ease of handling &
finishingfinishing
Cobalt – Chromium- NickelCobalt – Chromium- Nickel
Nickel is added to form strengthening phasesNickel is added to form strengthening phases

Noble MetalsNoble Metals
 These are elements with good metallic lustre thatThese are elements with good metallic lustre that
retain their surface in dry airretain their surface in dry air
 They react easily with sulfur to form sulfides, butThey react easily with sulfur to form sulfides, but
their resistance to oxidation, tarnish & corrosiontheir resistance to oxidation, tarnish & corrosion
during heating, casting soldering or use in mouthduring heating, casting soldering or use in mouth
is very goodis very good
 The noble metals are gold, platinum, palladium,The noble metals are gold, platinum, palladium,
iridium, rhodium, osmium & ruthenium. Silver isiridium, rhodium, osmium & ruthenium. Silver is
not considered in this categorynot considered in this category

Gold (Au)Gold (Au)
 Pure Gold is soft, malleable, ductile metal withPure Gold is soft, malleable, ductile metal with
rich yellow color % strong lustrerich yellow color % strong lustre
 Melts at 1064 c & has a density of 19.32g/ccMelts at 1064 c & has a density of 19.32g/cc
 Presence of 0.2% Pb makes it extremely brittlePresence of 0.2% Pb makes it extremely brittle
 Addition of Ca improves its mechanicalAddition of Ca improves its mechanical
properties & Hg has harmful effectproperties & Hg has harmful effect
 Air or water at any temp do not tarnish Au.Air or water at any temp do not tarnish Au.
 Because Gold is nearly as soft as lead, it must beBecause Gold is nearly as soft as lead, it must be
alloyed with Cu, Pt & other metals to develop thealloyed with Cu, Pt & other metals to develop the
hardness, durability & elasticityhardness, durability & elasticity

Platinum (Pt)Platinum (Pt)
 Pt is a bluish white metal with a melting pointPt is a bluish white metal with a melting point
of 1772 c and a density of 21.45g/ccof 1772 c and a density of 21.45g/cc
 It is tough, ductile & malleableIt is tough, ductile & malleable
 Has hardness similar to copperHas hardness similar to copper
 Has numerous applications in dentistry due toHas numerous applications in dentistry due to
high fusing pt & resistance to oral conditionshigh fusing pt & resistance to oral conditions
& elevated temperatures& elevated temperatures
 It has got CTH close to porcelain & addsIt has got CTH close to porcelain & adds
greatly to hardness & elastic qualities of Augreatly to hardness & elastic qualities of Au
 It tends to lighten the color of yellow goldIt tends to lighten the color of yellow gold
based alloysbased alloys

Palladium (Pd)Palladium (Pd)
 It is a white metal somewhat lighter than Pt. It isIt is a white metal somewhat lighter than Pt. It is
malleable & ductile with a melting point of 1554 cmalleable & ductile with a melting point of 1554 c
& density of 12.02g/cc& density of 12.02g/cc
 Palladium has the quality of absorbing orPalladium has the quality of absorbing or
occluding large quantities of hydrogen gas whenoccluding large quantities of hydrogen gas when
heatedheated
 It is not used in pure state because it imparts manyIt is not used in pure state because it imparts many
of the properties of platinum to dental alloys and itof the properties of platinum to dental alloys and it
is cheaper its often used as a replacement foris cheaper its often used as a replacement for
platinumplatinum

Iridium (Ir), Ruthenium (Ru) &Iridium (Ir), Ruthenium (Ru) &
Rhodium (Rh)Rhodium (Rh)
 These are used as Grain refinersThese are used as Grain refiners
 A small grain size is desirable because itA small grain size is desirable because it
improves the mechanical properties of the alloysimproves the mechanical properties of the alloys
& improves the informity& improves the informity
 The grain refining properties of these elementsThe grain refining properties of these elements
occur largely because of their high meltingoccur largely because of their high melting
points thus these elements do not melt during thepoints thus these elements do not melt during the
casting of the alloys & serve as nucleatingcasting of the alloys & serve as nucleating
centers for the metal as it cools resulting in finecenters for the metal as it cools resulting in fine
grained alloy.grained alloy. www.indiandentalacademy.comwww.indiandentalacademy.com

Noble Dental AlloysNoble Dental Alloys
 The new ADA no 5 has classified the alloys inThe new ADA no 5 has classified the alloys in
much more inclusive mannermuch more inclusive manner
1)1) High Noble :High Noble : with a noble metal content ofwith a noble metal content of
>60 wt% & Au content >40% it includes Au->60 wt% & Au content >40% it includes Au-
Ag-Pt, Au-Cu-Ag-Pd-Ag-Pt, Au-Cu-Ag-Pd-II & Au-Cu-Ag-Pd-& Au-Cu-Ag-Pd-IIII
2)2) Noble :Noble : with a noble content of > 25% & nowith a noble content of > 25% & no
stipulation for Au it includes Au-Cu-Ag-Pd-stipulation for Au it includes Au-Cu-Ag-Pd-IIIIII
Au-Ag-Pd-In, Pd-Cu-Ga & Ag-PdAu-Ag-Pd-In, Pd-Cu-Ga & Ag-Pd
3)3) Predominantly base metal :Predominantly base metal : with a noblewith a noble
content of < 25%content of < 25%

CompositionComposition
 Zn is added primarily as oxygen scavengerZn is added primarily as oxygen scavenger
because Ag in the composition absorbs oxygenbecause Ag in the composition absorbs oxygen
 In, Sn, & Fe are additions that harden the alloysIn, Sn, & Fe are additions that harden the alloys
Ga is added to compensate for COTGa is added to compensate for COT
 All modern alloys are fine grain this isAll modern alloys are fine grain this is
accomplished by addition of Ru, Ir & Rhaccomplished by addition of Ru, Ir & Rh
 Au, Ag, & Pd are soluble in solid state & all areAu, Ag, & Pd are soluble in solid state & all are
Face centered cubic so alloys are Face centeredFace centered cubic so alloys are Face centered
 Cu is principal hardener it reddens the alloyCu is principal hardener it reddens the alloy
which is minimized by silverwhich is minimized by silver

Lower Au content alloysLower Au content alloys
 Pd was specific in rendering the Ag in Au alloysPd was specific in rendering the Ag in Au alloys
tarnish resistant. For low Au composition abouttarnish resistant. For low Au composition about
1% Pd was needed for every 3% Ag to offset1% Pd was needed for every 3% Ag to offset
tarnish propensity of the silvertarnish propensity of the silver
 The Ag : Cu ratio has to be carefully balanced theThe Ag : Cu ratio has to be carefully balanced the
new alloy contained 42%Au, 25%Ag & 9% Cunew alloy contained 42%Au, 25%Ag & 9% Cu
 The major difference between the Type III &The major difference between the Type III &
Type IV Ag-Pd white alloys is that latter can beType IV Ag-Pd white alloys is that latter can be
age hardened by heat treating because of its Au &age hardened by heat treating because of its Au &
Cu contentCu content

Heat Treatment of Noble MetalsHeat Treatment of Noble Metals
 Gold alloys can be hardened if alloys containsGold alloys can be hardened if alloys contains
sufficient amount of coppersufficient amount of copper
 Type I & II alloys usually do not harden, or theyType I & II alloys usually do not harden, or they
harden to a lesser degree than Type III & IVharden to a lesser degree than Type III & IV
 Actual mechanism of hardening is solid- solidActual mechanism of hardening is solid- solid
transformations & criteria are Time & Temptransformations & criteria are Time & Temp
 Alloys that can be hardened can also beAlloys that can be hardened can also be
softened the softening heat treatment is referredsoftened the softening heat treatment is referred
to as solution heat treatment & hardening heatto as solution heat treatment & hardening heat
treatment is termed age hardening.treatment is termed age hardening.

Softening Heat TreatmentSoftening Heat Treatment
 The casting is placed in an electric furnace forThe casting is placed in an electric furnace for
10min at a temp of 70010min at a temp of 70000
c(1292c(129200
F) &then it isF) &then it is
quenched in water.quenched in water.
 During this period, all intermediate phases areDuring this period, all intermediate phases are
presumably changed to a disordered solid soln,presumably changed to a disordered solid soln,
and rapid prevents ordering from occurringand rapid prevents ordering from occurring
during cooling. The tensile strength, proportionalduring cooling. The tensile strength, proportional
limit, and hardness are reduced by such treatmentlimit, and hardness are reduced by such treatment
but the ductility is increasedbut the ductility is increased

Hardening Heat TreatmentHardening Heat Treatment
 This can be accomplished in many waysThis can be accomplished in many ways
 Most practical is by soaking or aging the casting atMost practical is by soaking or aging the casting at
a specific temperature for a definite time, usuallya specific temperature for a definite time, usually
15 to 30 min before it is water quenched15 to 30 min before it is water quenched
 The aging temp depends on alloy composition &The aging temp depends on alloy composition &
is generally between 200is generally between 20000
c to 450c to 45000
cc
 Before the age hardening alloy should beBefore the age hardening alloy should be
subjected to softening heat treatment. Thesubjected to softening heat treatment. The
hardening treatment is indicated for metallichardening treatment is indicated for metallic
partial dentures, saddles, bridges & similarpartial dentures, saddles, bridges & similar
structures for inlays it is not usually employedstructures for inlays it is not usually employed

Grain SizeGrain Size
 By the addition of small amounts (50ppm) ofBy the addition of small amounts (50ppm) of
elements such as iridium & ruthenium, fineelements such as iridium & ruthenium, fine
grain castings are producedgrain castings are produced
 The mechanical properties of tensile strengthThe mechanical properties of tensile strength
& elongation are improved significantly (30%)& elongation are improved significantly (30%)
by the fine grain structure in castings, whichby the fine grain structure in castings, which
contributes to uniformity of properties fromcontributes to uniformity of properties from
one casting to otherone casting to other
 Hardness & yield strength, show less effectHardness & yield strength, show less effect
from the grain refinementfrom the grain refinement

PropertiesProperties
Melting RangeMelting Range
 Dental casting alloys do not have melting pts theyDental casting alloys do not have melting pts they
have range because these are not pure metalshave range because these are not pure metals
 The diff between solidus & liquidus temp shouldThe diff between solidus & liquidus temp should
be narrow most of the alloys have 70be narrow most of the alloys have 7000
c or lessc or less
 The Au-Ag-Pt, Pd-Cu-Ga & Ag-Pd alloys haveThe Au-Ag-Pt, Pd-Cu-Ga & Ag-Pd alloys have
wider ranges which makes them diff to castwider ranges which makes them diff to cast
 The liquidus temp determines their burnout temp,The liquidus temp determines their burnout temp,
the type of investment & type of heat source usedthe type of investment & type of heat source used
during castingduring casting

 In general the burnout temp must be about 500In general the burnout temp must be about 50000
cc
belowbelow liquidus temp thus for the Au-Cu-Ag-Pd-liquidus temp thus for the Au-Cu-Ag-Pd-II
alloys the temp is 450-475alloys the temp is 450-47500
cc
 If the burnout temp reaches 700If the burnout temp reaches 70000
c then Gypsumc then Gypsum
bonded investment cannot be used becausebonded investment cannot be used because
Calcium sulfate will decompose & embrittle alloysCalcium sulfate will decompose & embrittle alloys
 At temp > 700At temp > 70000
c phosphate bonded is usedc phosphate bonded is used
 Gypsum bonded investment can be used for Au-Gypsum bonded investment can be used for Au-
Cu-Ag-Pd-Cu-Ag-Pd-I-II-IIII-II-III & Au-Ag-Pd-In& Au-Ag-Pd-In alloysalloys
 The Gas air torch will adequately heat alloys withThe Gas air torch will adequately heat alloys with
liquidus temp below 1100liquidus temp below 110000
c so it can be used forc so it can be used for
Au-Cu-Ag-Pd-Au-Cu-Ag-Pd-I-II-IIII-II-III & Au-Ag-Pd-In& Au-Ag-Pd-In alloysalloys
otherwise Gas oxygen torch or electric inductionotherwise Gas oxygen torch or electric induction
is usedis used www.indiandentalacademy.comwww.indiandentalacademy.com

 The liquidus temp is determined byThe liquidus temp is determined by
composition of alloyscomposition of alloys
 If the alloy contains a significant element thatIf the alloy contains a significant element that
has a high melting pt, then the alloy is likely tohas a high melting pt, then the alloy is likely to
have a high liquidus temphave a high liquidus temp
 Thus the alloys containing significant amountsThus the alloys containing significant amounts
of Pt or Pd have a high liquidus temp theseof Pt or Pd have a high liquidus temp these
include Pd-Cu-Ga, Ag-Pd & Au-Ag-Pt alloysinclude Pd-Cu-Ga, Ag-Pd & Au-Ag-Pt alloys

DensityDensity
 It is important during the acceleration of moltenIt is important during the acceleration of molten
alloy in to the mold during castingalloy in to the mold during casting
 Alloys with high density form complete castingAlloys with high density form complete casting
these are mainly containing Au & Ptthese are mainly containing Au & Pt
 Lower densities (7-8g/cc) seen in theLower densities (7-8g/cc) seen in the
predominantly base metals pose a problem duringpredominantly base metals pose a problem during
castingcasting
 Thus the Au-Ag-Pt & Au-Cu-Ag-Pd-Thus the Au-Ag-Pt & Au-Cu-Ag-Pd-II alloys arealloys are
among the most dense of the casting alloysamong the most dense of the casting alloys

StrengthStrength
 Strength of the alloys can be measured by theStrength of the alloys can be measured by the
either the yield strength or tensile strength.either the yield strength or tensile strength.
 Yield strength is more applicable in dentistry as itYield strength is more applicable in dentistry as it
implies the stress at which permanent deformationimplies the stress at which permanent deformation
of the alloys occurof the alloys occur
 Formation of ordered phase increases yieldFormation of ordered phase increases yield
strengthstrength

Hardness
 It is a indicator of ability of material to resistIt is a indicator of ability of material to resist
local permanent deformation under occlusallocal permanent deformation under occlusal
load it is similar to Yield strengthload it is similar to Yield strength
 Alloys having greater hardness create problemAlloys having greater hardness create problem
during polishing these are alloys mainlyduring polishing these are alloys mainly
containing Pdcontaining Pd
 The hardness of most of noble casting alloys isThe hardness of most of noble casting alloys is
less than that of enamel (343kg/mmless than that of enamel (343kg/mm22
))
otherwise they will tend to wear the enamelotherwise they will tend to wear the enamel

Elongation
 It is a measure of ductility of an alloyIt is a measure of ductility of an alloy
 For crown & bridge alloys value of elongationFor crown & bridge alloys value of elongation
is no concernis no concern
 Alloys with high elongation can be burnishedAlloys with high elongation can be burnished
easilyeasily
 In the soft conditions elongation of nobleIn the soft conditions elongation of noble
casting alloys is (8-30%) its more than basecasting alloys is (8-30%) its more than base
metals (1-2%)metals (1-2%)

Base MetalsBase Metals
 These are combined with noble metals toThese are combined with noble metals to
develop alloys with properties that are suitabledevelop alloys with properties that are suitable
for dental restorationsfor dental restorations
 Base metal alloys used in dentistry includeBase metal alloys used in dentistry include
silver, copper, zinc, indium, tin, gallium, &silver, copper, zinc, indium, tin, gallium, &
nickelnickel

 Dental applications of cast &Dental applications of cast &
wrought base metal alloyswrought base metal alloys
1)1) Cast Co-Cr alloys :Cast Co-Cr alloys : Partial denturePartial denture
framework & porcelain – metal restorationsframework & porcelain – metal restorations
2)2) Cast Ni-Cr alloys :Cast Ni-Cr alloys : Partial denturePartial denture
framework, Crowns & Bridges & porcelain –framework, Crowns & Bridges & porcelain –
metal restorationsmetal restorations
3)3) Cast Titanium % Titanium alloys :Cast Titanium % Titanium alloys :
Partial dentures & ImplantsPartial dentures & Implantswww.indiandentalacademy.comwww.indiandentalacademy.com

4)4) WroughtWrought Titanium % Titanium alloys :Titanium % Titanium alloys :
Partial DenturesPartial Dentures & Implants& Implants
5)5) Wrought stainless steel alloys :Wrought stainless steel alloys :
Endodontic instruments, Orthodontic wires &Endodontic instruments, Orthodontic wires &
brackets Preformed crownsbrackets Preformed crowns
6)6) Wrought Co-Cr-Ni alloys :Wrought Co-Cr-Ni alloys : OrthodonticOrthodontic
wires & Endodontic fileswires & Endodontic files
7)7) Wrought Ni-Ti alloys :Wrought Ni-Ti alloys : Orthodontic wires &Orthodontic wires &
Endodontic filesEndodontic files
8)8) Wrought beta – titanium alloys :Wrought beta – titanium alloys :
Orthodontic wiresOrthodontic wires

General Requirements for AlloyGeneral Requirements for Alloy
 It should not be toxic & allergic to patient &It should not be toxic & allergic to patient &
operatoroperator
 It should be resistant to corrosion & physicalIt should be resistant to corrosion & physical
changes when it is in oral fluidschanges when it is in oral fluids
 The physical & mechanical properties, such asThe physical & mechanical properties, such as
conductivity, melting temp, COT, & strengthconductivity, melting temp, COT, & strength
should be satisfactoryshould be satisfactory
 The technical expertise needed for fabrication &The technical expertise needed for fabrication &
use should all be feasible for the average dentistuse should all be feasible for the average dentist
& skilled dentist& skilled dentist
 They should be inexpensive & readily availableThey should be inexpensive & readily availablewww.indiandentalacademy.comwww.indiandentalacademy.com

Silver (Ag)Silver (Ag)
 Is a white metal that is malleable & ductile & hasIs a white metal that is malleable & ductile & has
density of 10.49g/cc & melting pt of 961.9 cdensity of 10.49g/cc & melting pt of 961.9 c
 Best known conductor of heat and electricity, isBest known conductor of heat and electricity, is
stronger & harder than Au, but is softer than Custronger & harder than Au, but is softer than Cu
 Foods containing sulfur compounds cause severeFoods containing sulfur compounds cause severe
tarnish on silver it occludes appreciable amountstarnish on silver it occludes appreciable amounts
of oxygen in molten state this can be reduced byof oxygen in molten state this can be reduced by
addition of 5 – 10% Cuaddition of 5 – 10% Cu
 Ag forms a series of solid soln with both Au &Ag forms a series of solid soln with both Au &
Pd its therefore common in Au & Pd basedPd its therefore common in Au & Pd based
alloys it also hardens goldalloys it also hardens goldwww.indiandentalacademy.comwww.indiandentalacademy.com

Copper (Cu)Copper (Cu)
 Is a red color metal with 8.92g/cc density &Is a red color metal with 8.92g/cc density &
1083.4 c1083.4 c
 Cu forms a series of solid soln with both Au & PdCu forms a series of solid soln with both Au & Pd
 When added to Au based alloys Cu imparts aWhen added to Au based alloys Cu imparts a
reddish color & hardens the alloyreddish color & hardens the alloy
 It is used in Pd bases alloys to reduce melting ptIt is used in Pd bases alloys to reduce melting pt
& strengthen the alloy& strengthen the alloy
 The ratio of Ag & Cu must be carefully balancedThe ratio of Ag & Cu must be carefully balanced
in both Au & Pd based alloys because these arein both Au & Pd based alloys because these are
not mutually misciblenot mutually miscible

Zinc (Zn)Zinc (Zn)
 It is a blue white metal with a tendency to tarnish inIt is a blue white metal with a tendency to tarnish in
moist airmoist air
 Melts at 419.6 c & has density of 7.14g/ccMelts at 419.6 c & has density of 7.14g/cc
 In its pure form it is a soft, brittle metal with lowIn its pure form it is a soft, brittle metal with low
strength when heated in air it oxidizes to form astrength when heated in air it oxidizes to form a
white oxide of low densitywhite oxide of low density
 Although it may be present in 1 -2% it acts as aAlthough it may be present in 1 -2% it acts as a
deoxidizing agent because of its low density thedeoxidizing agent because of its low density the
resulting zinc oxide lags behind the denser moltenresulting zinc oxide lags behind the denser molten
mass during casting & is therefore excluded frommass during casting & is therefore excluded from
the castingthe casting if present in large amounts it makes alloyif present in large amounts it makes alloy
brittlebrittle www.indiandentalacademy.comwww.indiandentalacademy.com

Indium (In)Indium (In)
 Is a soft gray white metal with a low melting ptIs a soft gray white metal with a low melting pt
of 156.6 c & density of 7.31g/ccof 156.6 c & density of 7.31g/cc
 Indium is not tarnished by air or water it is usedIndium is not tarnished by air or water it is used
in some Gold based alloys as replacement for Znin some Gold based alloys as replacement for Zn
 Recently it is used in greater amounts in ( up toRecently it is used in greater amounts in ( up to
30%) in Pd – Ag alloys to impart a yellow color30%) in Pd – Ag alloys to impart a yellow color
to metalto metal

Tin (Sn)Tin (Sn)
 It is lustrous, soft white metal that is notIt is lustrous, soft white metal that is not
subject to tarnish in normal airsubject to tarnish in normal air
 Has melting pt of 232 c & density of 7.29g/ccHas melting pt of 232 c & density of 7.29g/cc
 Some Au based alloys contain limited amountsSome Au based alloys contain limited amounts
of tin usually 5% by weightof tin usually 5% by weight

Gallium (Ga)Gallium (Ga)
 It is a grayish metal that is stable in dry air butIt is a grayish metal that is stable in dry air but
tarnishes in moist air.tarnishes in moist air.
 It has very low melting pt of 29.8 c & densityIt has very low melting pt of 29.8 c & density
of 5.91g/ccof 5.91g/cc
 Its not used in pure form in dentistry but isIts not used in pure form in dentistry but is
used as component in some Au- & Pd- basedused as component in some Au- & Pd- based
alloys especially in ceramic alloysalloys especially in ceramic alloys
 The oxides of Ga are important to the bondingThe oxides of Ga are important to the bonding
of the ceramic to metalof the ceramic to metal

Nickel (Ni)
 Common component of non noble alloysCommon component of non noble alloys
 Has a melting pt of 1453 c & density ofHas a melting pt of 1453 c & density of
8.91g/cc8.91g/cc
 When used in small quantities in gold basedWhen used in small quantities in gold based
alloys, nickel whitens the alloy & increases itsalloys, nickel whitens the alloy & increases its
hardness & strengthhardness & strength

Composition & PropertiesComposition & Properties
Composition of major Base Metal alloysComposition of major Base Metal alloys
ElementsElements VitalliumVitallium TiconiumTiconium
1)1) Cr 30% 17%Cr 30% 17%
2)2) Co Balance -Co Balance -
3)3) Ni - BalanceNi - Balance
4)4) Mb 5% 5%Mb 5% 5%
5)5) Al - 5%Al - 5%
6)6) Fe 1% 0.5%Fe 1% 0.5%
7)7) C 0.5% 0.1%C 0.5% 0.1%
8)8) Be - 1%Be - 1%
9)9) Si 0.6% 0.5%Si 0.6% 0.5%
10)10) Mn 0.5% 5%Mn 0.5% 5%www.indiandentalacademy.comwww.indiandentalacademy.com

PropertiesProperties
Melting TemperatureMelting Temperature
 These melt at temp of 1400These melt at temp of 140000
c to 1500c to 150000
c asc as
compared to cast Gold alloys (800-1050compared to cast Gold alloys (800-105000
))
 Only Ticonium melts at below 1300 c, at temp ofOnly Ticonium melts at below 1300 c, at temp of
1275c addition of Be lowers the melting temp of1275c addition of Be lowers the melting temp of
Ni-Cr alloys about 100cNi-Cr alloys about 100c
 The melting temp is important in the selection ofThe melting temp is important in the selection of
casting equipment & control of the castingcasting equipment & control of the casting
TechniqueTechnique

StrengthStrength
 The dental alloys should have a yield strength ofThe dental alloys should have a yield strength of
at least 415Mpaat least 415Mpa
 Usually base metal alloys have yield strengthUsually base metal alloys have yield strength
greater than 600Mpagreater than 600Mpa
 The tensile strength of these metals is more thanThe tensile strength of these metals is more than
800Mpa800Mpa

Crown & Bridge Casting AlloysCrown & Bridge Casting Alloys
 The Ni-Cr alloys can be divided in to thoseThe Ni-Cr alloys can be divided in to those
containing or not containing Becontaining or not containing Be
 Most of the alloys contain 60-80% Ni, 10-27%Cr &Most of the alloys contain 60-80% Ni, 10-27%Cr &
2-14% Mb2-14% Mb
 Co-Cr alloys contain 53-57% Co, 25-32%Cr & 2-Co-Cr alloys contain 53-57% Co, 25-32%Cr & 2-
6% Mb they may also contain Al, C, Co, Cu, Ga,6% Mb they may also contain Al, C, Co, Cu, Ga,
Fe, Mn, Si, Sn, Ti & ZrFe, Mn, Si, Sn, Ti & Zr
 Those containing Be the % is 1.6% to 2%Those containing Be the % is 1.6% to 2%
 These exhibit more hardness & elastic modulusThese exhibit more hardness & elastic modulus
 More technique sensitive difficult to cast due toMore technique sensitive difficult to cast due to
higher solidification shrinkagehigher solidification shrinkage

 Alloys containing Be & Ni should be protectedAlloys containing Be & Ni should be protected
from metallic vapor, dust or grindingsfrom metallic vapor, dust or grindings
responses include contact dermatitis to severeresponses include contact dermatitis to severe
pneumoniapneumonia
 Ni is believed to be allergen allergy is higherNi is believed to be allergen allergy is higher
in females than for malesin females than for males
 Ni based alloys should be avoided in patientsNi based alloys should be avoided in patients
with known allergywith known allergy

Japanese GoldJapanese Gold
 It’s a Copper based non precious casting alloyIt’s a Copper based non precious casting alloy
 Also referred as Orden Golden Casting AlloyAlso referred as Orden Golden Casting Alloy
CompositionComposition
 Cu – 53.04%, Zn – 45%, Al-1.3% Fe-0.2%Cu – 53.04%, Zn – 45%, Al-1.3% Fe-0.2%
 V.H.N -181-182, Density – 8.1g/cc &V.H.N -181-182, Density – 8.1g/cc &
Elongation% is 6%Elongation% is 6%

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