Dental Casting alloy for Dentistry

1. Dental Casting Alloys
By
Dr. Mujtaba Ashraf
JR-1
Department of Prosthodontics
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2. Contents:
Introduction
Historical Perspective
Desirable Properties
Composition
Classification
Noble Metal Alloys
Base Metal Alloys
Guidelines for the selection of alloys
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3. Introduction:
Today the dental profession has access to a wide
variety of casting alloys.
These alloys are designed for specific clinical
purposes like:
. Inlays
. Onlays
. Crowns
. Bridges
. Partial dentures; and
. Porcelain fused to metal restorations.
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4. ALLOY :
A mixture of two or more metals or metalloids that are
mutually soluble in the molten state; distinguished as
binary, ternary, quaternary, etc., depending on the number
of metals within the mixture.
Alloying elements are added to alter the
hardness, strength, and toughness of a metallic element,
thus obtaining properties not found in a pure metal.
*GPT8
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5. Casting:
Something that has been cast in a mold; an object
formed by the solidification of a fluid that has been
poured or injected into a mold.
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6. Historical Perspective on Dental Casting Alloys
Year Event
1789 Jean Darcet introduced Low-fusing metal alloy
1907 Introduction of Lost-Wax Technique by W.H.Taggart
1933 Replacement of Co-Cr for Gold in Removable Partial
Denture
1950 Development of Resin Veneers for Gold Alloys
1959 Introduction of the Porcelain Fused-to-Metal Technique
1968 Palladium-Based Alloys as Alternatives to Gold Alloy
1971 Nickel-Based Alloys as Alternatives to Gold Alloys
1980s Introduction of All-Ceramic Technologies
1999 Gold Alloys as Alternatives to Palladium-Based Alloys
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7. Desirable Properties of Dental Casting Alloys
All casting alloys must first be biocompatible and
then exhibit sufficient physical and mechanical
properties to ensure adequate function and structural
durability over long periods of time.
Depending on the primary purpose of the prosthesis,
such as to restore function, enhance aesthetics, or
maintain occlusion, the choice of casting alloy or
metal is made.
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8. Some of the clinically important properties and
requirements of the alloys are :
Biocompatibility: The alloy should not react with
the oral fluids and release any harmful products in
oral environment.
Resistance to tarnish: Tarnish is a thin film of a
surface deposit or an interaction layer that is adherent
to the metal surface. Tarnish is usually on silver
alloys and on gold alloys with higher silver content.
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9. Resistance to corrosion: Corrosion may lead to
catastrophic failure; oxidized components may
discolor natural teeth, porcelain veneers and soft
tissues.
Corrosion also contribute to galvanic shock due to
the electrons released during corrosion.
Released metallic components may cause metallic
taste in the mouth.
The presence of noble metals in alloy increases
resistance to corrosion.
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10. Nonallergenic: Although toxic materials are
eliminated from the alloys. However, some
individuals exhibits allergic reactions to some
components. Since these allergic reactions are
peculiar to the individual patient, the dentist
should have a record of all the components of the
alloy that is being used and should inform the
patient accordingly.
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11. Aesthetics: The alloys must be in optimal balance
among the properties of aesthetics, fit, abrasive
potential and clinical survivability.
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12. Thermal Properties: For metal-ceramic
restorations, the alloys or metals must have
closely matching thermal expansion to be
compatible with a given porcelain, and they must
tolerate high processing temperatures.
The melting range of alloys must be low enough
to form smooth surfaces with the mold walls of
the investment.
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13. Liquidus and solidus temperatures:
Liquidus temperature: Temperature at which an alloy
begins to freeze on cooling or at which the metal is
completely molten on heating.
Solidus temperature: Temperature at which an alloy
becomes solid on cooling or at which the metal begins
to melt on heating.
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14. Hence we can say that the melting of the alloys
starts at solidus temperature and is completed at
liquidus temperature.
An alloy must be heated above its liquidus to be
cast successfully.
Alloys with the lower the solidus temperature is
preferred as the lower shrinkage occurs during
cooling.
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15. Hardness: The hardness of an alloy should
be sufficient enough to resist wear by the
opposing tooth or restoration.
At the same time, it should not be high enough to
cause wear of the opposing enamel
(VHN of enamel is 340 kg/mm²).
Hardness of an alloy should not be less than 125
kg/mm² or greater than 340 kg/mm².
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16. Ease of fabrication: The material should be easily
manipulated and the procedure for fabrication
should not be too complicated and lengthy.
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17. Castability: To achieve accurate details in a cast
framework or prosthesis, the molten metal must
able to wet the investment mold material very
well and flow into the most intricate regions of the
mold without any appreciable interaction with the
investment and without forming porosity within
the surface or sub surface region.
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18. Finishing of cast metal: Some metals are harder,
hence more difficult to finish and polish.
Some noble metal alloys are more ductile and
malleable, hence care should be taken during
finishing of the casting.
The hardness of an alloy is a good indicator of the
difficulty in grinding and finishing of
the alloy.
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19. Porcelain Bonding: The alloy used in metal-
ceramic restorations should be able to form a
thin, adherent layer of oxide on its surface to
enable proper bonding with ceramic.
The alloy must have a coefficient of thermal
expansion/contraction closely matching to that
of ceramic so as to create compressive stresses
to enhance fracture resistance of the ceramic.
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20. Composition of Dental Casting Alloys
Various metallic elements are combined in
different proportions to produce alloys with
adequate properties for dental applications.
The metals that are used to make dental alloys are
broadly of two major groups:
Noble metals and
Base metals
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21. Noble Metal Alloys
The periodic table of the elements shows eight
noble metals:
gold, the platinum group metals (platinum,
palladium, rhodium, ruthenium, iridium,
osmium), and silver.
However, silver is more reactive in the oral
cavity and is not considered a noble metal.
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22. 22Mujtaba Ashraf

23. GOLD
•Gold, a soft, yellow metal,
is the most ductile and
malleable of all metals but
it has much lower strength.
•Density 19.3g/cm³
•Melting point 1063°C
•Resistance to corrosion
•High burnishability
•Low yield strength
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24. Platinum, a bluish-white metal
is tough, ductile and
malleable.
•Its hardness is similar to that
of copper
•Density 21.37g/cm³
•Melting point 1755°C
(highest)
•Elevates fusion temperature
•Elevates strength
•Whitens the alloy
PLATINUM
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25. PALLADIUM
•Palladium, a white metal
•It whitens the alloy, any gold
alloy containing more than 6%
palladium will be white.
•Density 11.4g/cm3
•Melting point 1555°C
•Enhance mechanical properties
such as hardness and tensile
strength
Disadvantage: At elevated temperature, it has a great
affinity for hydrogen gas. Consequently high Pd content
castings may causes internal porosity by absorbing large
amount gas, if not cast under ideal conditions. 25Mujtaba Ashraf

26. Other Noble Metals
Iridium (Ir) and ruthenium are used in small
amounts in dental alloys as grain refiners to keep
the grain size small. A small grain size is desirable
because it improves the mechanical properties and
uniformity of properties within an alloy
Osmium (Os) has very high melting point and
extreme cost, so are not used in dental casting
alloys .
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27. Rhodium (Rh) also has a high melting point
(1966°C) and has been used in alloys with platinum
to form wire for thermocouples.
These thermocouples help measure the temperature
in porcelain furnaces used to make dental
restorations.
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28. Base Metal Alloys
•Base metals used in dental alloys include
silver, copper, zinc, indium, tin, gallium, and
nickel.
•Uses
Fabrication of partial denture frame work
As casting and wrought alloys
Surgical instruments
Periodontal splints
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29. SILVER (Ag)
•Silver is a malleable, ductile white metal.
•It is the best-known conductor of heat and electricity.
•Stronger and harder than gold but softer than copper.
•Density 10.4gms/cm3
•Melting point 961oC
• It is unaltered in clean, dry air at any temperature, but
combines with sulfur, chlorine, phosphorus, and vapors
containing these elements or their compounds.
•Foods containing sulfur compounds cause severe tarnish
on silver, and for this reason silver is not considered a
noble metal in dentistry.
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30. COPPER (Cu)
•Copper is a malleable and ductile metal with
high thermal and electrical conductivity
•A characteristic red color.
•Copper forms a series of solid solutions
•with both gold and palladium and is therefore
an important component of noble dental
alloys.
•Melting point of 1083°C
•Density of 8.96 gm/cm³
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31. ZINC (Zn)
Zinc is a blue-white metal with a tendency to
tarnish in moist air.
In its pure form, it is a soft, brittle metal with
low strength.
When heated in air, zinc oxidizes readily to
form a white oxide of relatively low density.
This oxidizing property is exploited in
dental alloys.
Although zinc may be present in quantities
of only 1% to 2% by weight, it acts as a
scavenger of oxygen when the alloy is melted.
Thus zinc is referred to as a deoxidizing agent.
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32. INDIUM (In)
•Indium is a soft, gray-white metal.
• Low melting point of 156.6° C.
•Indium is not tarnished by air or water.
•It is used in some gold-based alloys as a
•replacement for zinc and is a common minor
component of some noble ceramic dental
alloys.
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33. TIN (Sn)
•Tin is a lustrous, soft, white metal
•Not to tarnish in normal air.
•Some gold-based alloys contain limited
quantities of tin, usually less than 5% by weight.
•Tin is also an ingredient in gold-based dental
solders.
•It combines with platinum and palladium to
produce a hardening effect, but also increases
brittleness.
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34. GALLIUM (Ga)
•Gallium is a grayish metal.
•Stable in dry air but tarnishes in moist air.
•It has a very low melting point of 29.8° C
•Density of only 5.91 g/cm3.
•Gallium is not used in its pure form in dentistry,
but is used as a component of some gold- and
palladium based dental alloys, especially ceramic
alloys.
•The oxides of gallium are important to the
bonding of the ceramic to the metal.
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35. NICKEL (Ni)
•Nickel has limited application in gold- and
palladium-based dental alloys, but is a common
component in nonnoble dental alloys.
•Melting point 1453° C
•Density of 8.91 g/cm3.
•When used in small quantities in gold-based
alloys, nickel whitens the alloy and increases its
strength and hardness.
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36. Classification of Noble Metal Alloys
All noble metal alloys have either gold or platinum as the
principal metal by weight percentage.
There are several classifications for dental casting alloys.
The first (i.e. alloy type by nobility) being the simple
classification given by ADA in 1984.
Three categories are described
•high noble (HN),
•noble (N), and
•predominantly base metal (PB).
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37. Alloy type by nobility
A. Category I - High noble (HN) Alloys
contain > 60 wt% of noble metals (Au > 40 wt%)
B. Category II noble (N) Alloys
contain > 25 wt% of noble metals.
C. Category III predominantly base metal (PB) alloys
contain < 25 wt% of noble metals.
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38. Properties of High noble alloys
•These alloys are the most expensive as gold, palladium and
platinum are expensive
•Have relatively high densities that make them easier to cast
•Due to high liquidus ( high melting point) allows them to serve
as alloys for porcelain bonded restoration.
•Low corrosion properties
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39. Properties of Noble alloys
•Moderate densities 10 to 12g/cm3
•Corrosion resistance slight lower than HN alloy
•Cost of these alloys are less than NH alloy
•Used for crown or bridges with or without porcelain covering.
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40. Properties of base metal alloys
Extremely high yield strengths and hardness,
makes difficult to polish.
Less corrosion resistance.
Less biocompatible .
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41. Classification by Bureau of Standard, 1927:
Alloys can also be classified into four types according to
their composition, their use, and the amount of stress they
will be subjected to.
This is the most prevalent classification.
The hardness increases from type I to type IV.
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42. A. Type I (soft-low strength):
• Used for fabrication of castings
subjected to minimal stress.
• Minimum yield strength is 80 Mpa
• Minimum percent elongation 18%
• Used as inlays and class III and class V
restorations.
• These alloys are easily burnishable.
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43. B. Type II (medium- medium strength);
•Used for fabrication of castings subjected to moderate
stresses
•Used for inlays, full crowns, onlays, and thick 3/4th
crowns.
•The minimum yield strength is 180 Mpa.
•The minimum percent elongation is 10%.
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44. C. Type III (hard high strength):
•For castings subjected to high stress.
•Used for fabrication of onlays, thin copings,
thin 3/4th crowns, pontics, full crowns, and
saddles.
•The minimum yield strength is 270 Mpa.
•The minimum percent elongation is 5%.
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45. D. Type IV (extra hard- very high strength):
•Used for castings subjected to very high stresses
such as saddles, bars, clasps, partial denture
framework, and long span bridge framework.
•The minimum yield strength is 300 Mpa.
•The minimum percent elongation is 3%.
Types 1 and 2 alloys are often referred to as inlay alloys.
Types 3 and 4 alloys are generally called crown and bridge alloys.
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46. The alloys for metal-ceramic restorations can be used for
all-metal (or resin-veneer) prostheses, whereas the alloys
for all-metal restorations should not be used for metal-
ceramic restorations.
The reasons are as follows:
(1)The alloys may not form thin, stable oxide layers to
promote atomic bonding to porcelain.
(2)Their melting range may be too low to resist sag
deformation or melting at porcelain filing
temperatures.
( 3 ) Their thermal contraction coefficients may not be
close enough to those of commercial porcelains
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47. Carat and Fineness
•For many years, noble alloys were described on the basis of
their gold content, in terms of carat and fineness.
•Both refer only to the gold content of the alloy.
•Carat represents 1/24th part of the whole.
•For example, 24-carat gold is pure (100% gold), whereas
22-carat gold (91.67% gold) is an alloy containing 22 parts
pure gold and 2 parts of other metals.
•Fineness represents the number of parts of gold in 1000
parts of the alloy.
•Pure gold is 1000 fine.
The use of these terms is less common nowadays.
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48. ADA Specification No. 5 formerly classified gold alloys as types
1 to 4 depending on the content of gold, palladium, and platinum.
The content of noble metals by weight ranges from 83% (type 1)
to 75% (type 4).
Both the current ADA Specification No. 5 (1997) and ISO
Standard 1562 (2004) have classified four types of casting alloys
using similar minimal yield strength and percent elongation
values for each type of alloy.
Gold Based Alloy
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49. •Gold Based alloys are generally yellow in color .
•Type 1 gold alloys
•Relatively Soft
•Au-83%; Ag-10%; Pd-0.5%; Cu-6%;
Ga,In, & Zn-Balance
•Soft and designed for inlays supported by teeth and not
subjected to significant mastication forces.
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50. •Type 2 gold alloys
•Medium strength
•Au-77%; Ag-14%; Pd-1%; Cu-7%;
Ga,In, & Zn-Balance
•Widely used for inlays because of their superior
mechanical properties, but they have less
ductility than type 1 alloys.
•Used for conventional inlays onlays or full
mouth crowns.
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51. •Type 3 gold alloys
•High Strength
•Au-75%; Ag-11%; Pd-3.5%; Cu-9%;
• Ga, In, & Zn-Balance
•Used for constructing crowns and onlays for
high-stress areas.
•Increasing the Pt or Pd content raises the
melting temperature, which is beneficial when
components are to be joined.
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52. Type 4 gold alloys
Extra High Strength
•Au-56%; Ag-25%; Pd-4%; Cu-14%;
Ga, In, & Zn-Balance
•Used in high-stress areas such as bridges and
partial denture frameworks.
•The cast alloy must be rigid to resist flexure.
•Possess high yield strength to prevent permanent
distortion, and be ductile enough for adjustment if
the clasp of a framework has been distorted or
needs adjustment.
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High Noble and Noble Alloys for
Metal Ceramic Prostheses
•Porcelain and ceramic materials have been used for
fabricating esthetic dental restorations since the early
1800s.
•The first published reports describing the successful
use of porcelain fused to alloys appeared in the mid-
1950s.

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Gold–platinum–palladium
(Au–Pt–Pd) alloys
•This was the first casting alloy formulated for use
with metal-ceramic restorations.
•This high noble alloy has a gold content of 8l%-87%;
• Pt 4.5%-10%, and Pd 5%-11%.
•The casting temperature is around l330°C-1335°C.

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•As with other high noble alloys, it has high
corrosion resistance.
•This alloy is used exclusively for metal-ceramic
prostheses (single crowns and short span
bridges), it is contraindicated in long span
bridges since its sag resistance is low and it is
susceptible to dimensional change.

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Gold–palladium–silver (Au–Pd–Ag) alloys
The Au–Pd–Ag alloys were developed in an attempt to
overcome
the major disadvantages of the Au–Pt–Pd alloys:
High cost, low hardness, and poor sag resistance.
Subdivided in two smaller groups:
High silver (More than 12% Ag) and
Low silver (5%-11.99% Ag)
The principle disadvantage of these alloys is the potential for
their silver content to discolor porcelain

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Greening
It is the general term applied to porcelain
that is discolored due to contamination with silver.
Tuccillo suggested that silver may be responsible for
staining when it evaporates as a positively charged ion
during porcelain firing.

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During firing the silver atoms enter the body
of the porcelain or diffuse through the glazed
surface and cause green, yellow-green, or
yellow-orange to brown discoloration.

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Prevention of greening:
Regular use of a graphite block to maintain a
reducing atmosphere near the alloy which
inhibits the formation of silver oxide.
A pure gold film is fired on the alloy surface;
this reduces the amount of free silver ions
available on the alloy surface for vaporization.

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Gold–palladium (Au–Pd) alloys
•The Au–Pd alloys were developed to address the
two main problems associated with silver-
containing alloys:
•Porcelain discoloration and
•a high coefficient of thermal expansion.
•Introduced by J.F. Jelenko & Co in 1977
•Contains 45%-52% Au and 37%-45% Pd

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These alloys exhibit a “white gold” color and have been
commercially successful.
The only significant disadvantage is having a
degree of thermal expansion incompatible with some high
expansion porcelains causes crack formation.
In an effort to address this problem,
a number of Au–Pd alloys have recently been developed that
contain less (<5% silver)
Due to these alloys low silver content,
porcelain does not discolor, castability is improved, and
the coefficient of thermal expansion is increased

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Palladium–silver (Pd–Ag) alloys
In 1974 the first “gold-free” noble-metal metal-
ceramic alloys, the Pd–Ag alloys, were introduced.
They were specifically developed to offer an
economical alternative to more expensive gold-based
alloys.

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The compositions Pd-Ag alloys fall within a
narrow range of 53% to 61% Pd and 28% to 40%
Ag.
Tin and/or indium are usually added to increase
alloy hardness and to promote oxide formation and
adequate bonding to porcelain.

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The high silver content compared with that of
gold-based alloys, the silver discoloration effect
is most severe for these alloys.
Gold metal conditioners or ceramic coating
agents may minimize this effect.
The elastic modulus for Pd–Ag alloys is the most
favorable of all of the noble-metal
metal-ceramic alloys as a result Pd–Ag alloys
have excellent sag resistance.

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High-palladium alloys
Several types of high-palladium alloys were
introduced in the
1980s.
These alloys were primarily developed for economic
reasons and to address biocompatibility concerns of
nickel-based casting alloys, and
to minimize the possibility of porcelain
discoloration.
The most popular types have been
Pd–Cu, Pd–Co, and Pd–Ga.

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Palladium-Gallium-Silver
Palladium-gallium-silver alloys is the most recent of the
noble metal alloys.
Advantages
• Slightly lighter colored oxide than the Pd-Cu alloys.
•Thermally compatible.
•Low hardness

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Base Metal Alloys
Metals that oxidize or dissolve readily to release ions.
Base metal alloys are primarily made of cobalt,
nickel, and/or titanium; though minor amounts of
noble metals may also be present.

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These alloys are more complex, science they
may contain 6-8 elements in addition to their
primary constituents including:
molybdenum, chromium, aluminum, vanadium,
iron, carbon, beryllium, manganese, gallium,
silicon, etc.

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Base-Metal Metal-Ceramic Alloy
Nickel-
Chromium
Beryllium
containing
Beryllium
free
Cobalt-
Chromium
Titanium
*(adapted from Naylor and O’Brien
Compositional classification of base-metal metal-ceramic alloys

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Historically, the base-metal alloys were divided
into four groups:
•nickel–chromium–beryllium,
•nickel–chromium,
•nickel–high-chromium, and
•cobalt–chromium

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Nickel–chromium–beryllium, nickel–chromium,
nickel–high-chromium are used for fabrication of
crowns and bridges (with and without ceramic).
while cobalt–chromium predominantly used for
removable partial dentures and dental implants.

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Nickel–chromium (Ni–Cr) alloys
Most common base metal alloy used in metal-
ceramic prostheses.
The composition includes:
•Nickel (61.5%-77.5%
•Chromium (12.8%-22%)
•Molybdenum (4%-14%)
•Aluminum (0%-4%), and
•Iron (0%-5%)
•Ni-Cr-Be alloys also contain 0%-2% beryllium

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•Yield strength is 260-830 MPa
•Hardness ranges between 175VHN -380 VHN
•Tensile strength 400-1200 MPa
•Modulus of elasticity 150-210 GPa
•Percentage elongation is 8%-28%

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•Chromium contributes to the corrosion resistance.
•Molybdenum decreases coefficient of thermal expansion.
•Nickel and aluminum form an intermetallic compound i.e
Ni₃Al that contributes to strength and hardness.
•Nickel is also a known allergen, more so in females
(4.5%) than males (1.5%).
•It results in contact dermatitis and hypersensitivity
•OSHA regulations allow 15 μg/m³ of Ni in air.

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Beryllium is primarily added to lowering the
melting range of the alloy, enhances fluidity, and
improves grain structure.

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•Beryllium is known to be toxic, more so to the
laboratory technician during alloy melting.
•Toxicity that is termed as berylliosis may be
exhibited from mild to moderate symptoms as
contact dermatitis to severe chemical pneumonitis.
•Permissible maximum concentration of Be in air
is 5 μg/m³, while Occupational Safety and Health
Act (OSHA) guidelines permit an exposure of a
maximum of 2 μg/m³.

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Reasons for the use of nickel-chromium alloys in
dentistry:
•Nickel is combined with chromium to form a highly
corrosion resistant alloy.
•It is low cost alloy as compared to Gold based alloys.
•Alloys such as Ticonium-100 have been used in
removable partial denture frameworks for many years with
few reports of allergic reactions.
•Nickel alloys have excellent mechanical properties,
such as high elastic modulus (stiffness), high hardness, and
a reasonably high elongation (ductility).

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Cobalt–chromium (Co–Cr) alloys
In 1907 Haynes patented cobalt-chromium.
In 1929 Co-Cr alloys were used in dental
appliances.
Cobalt is the main constituent of cobalt-based
metal-ceramic alloys, with chromium added for
strength and to provide corrosion resistance via
passivation.

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The composition of Co-Cr alloy is
Cobalt (52%-28%)
Chromium (15%-28%)
Tungsten (10%-14%)
Other trace elements are
Ga 0%-7%, Ru (0%-6%), Fe (0%-1%)
Cu (0%-1%)

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Yield strength is 460-640 MPa
Elastic modulus is 145-220 Gpa
Elongation is 6%-15%
Hardness is 330-465 VHN and
Tensile strength is 520-820 MPa.

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Cobalt–chromium alloys are the most common
base-metal alternative for patients known to be allergic
to nickel.
Second highest melting point of all dental casting alloy.
Disadvantages of Co-Cr alloys:
Difficult laboratory procedures ( casting, finishing,
polishing).
Incompatibility in CTE between Co-Cr alloy and
porcelain.

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Co-Cr alloys are used for the metal framework
of cast partial dentures, since they are much less
ductile than Ni-Cr.
These-alloys are not used for metal
ceramic prostheses, since the oxide layer formed
on these alloys are susceptible to delamination
and adversely affect the bonding with porcelain

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TITANIUM (Ti) AND TITANIUM ALLOYS
Titanium was discovered in the late 1700s and
is the fourth most abundant metal in the earth’s
crust .
Process for extracting of Titanium was
introduced by Kroll in 1936.

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Titanium has a number of advantages, such as
light weight, adequate strength, good corrosion
resistance, excellent biocompatibility.
Titanium alloys are being used as
dental implants
For implant prosthesis, cast partial dentures and
metal ceramic prostheses.

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Titanium based alloys containing 90% titanium, 6% aluminum
and 4% vanadium, hence this alloy is termed as Ti-6Al-4Va

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Due to its high melting range ( upto 1668°C), Ti-based
alloys are difficult to cast and requires a special Centrifugal
induction casting machine and argon atmosphere.
Pure Cp-Ti has tensile strength of 240-890MPa
Hardness 125-350VHN

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Titanium has highest melting point of all
metals and alloys used in dentistry
High fusion temperature and low CTE.
High corrosion resistance
Titanium forms porous and non-adherent
oxide layer which does not form reliable
porcelain to metal bond.

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GUIDELINES FOR THE SELECTION OF
ALLOYS
Choosing an alloy for prosthodontic
restorations is a formidable task.
Although there is no proven formula
for selection, practitioners may find the
following guidelines helpful.

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Develop an understanding of alloys
1. Avoid selecting an alloy based on its color unless
all other factors are equal.
2. Know the complete composition of alloys, and
avoid elements to which the patient is allergic. Know
the alloys that the laboratory uses; specify a specific
alloy in the laboratory prescription.

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3. When possible, use single-phase alloys over
multiple-phase alloys.
4. Keep track of alloys used in the patient with the
Identalloy system or something similar. At
minimum, the name of the alloy and the
manufacturer should be
recorded.

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Use clinically proven products from quality
Manufacturers
5. Use alloys from companies that research and
manufacture their own alloys. These companies will
be able to provide the most accurate information, the
best service, and the best answers when problems
arise.

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6. Use alloys that have been tested for elemental
release and corrosion and that have the lowest
possible release of elements.
7. Use a dental laboratory that is knowledgeable
about its alloys and willing to discuss issues about
them. Be comfortable with the alloys that the
laboratory uses.

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Develop a clinical philosophy
8. Focus on the long-term clinical performance and
long-term costs of restorations rather than on short
term costs.

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9. Consider the clinical situation (esthetics,
occlusion, space, and systemic allergy) when
selecting an alloy. Select the alloy that meets the
needs of the patient. Avoid a “one size fits all”
approach.
10. Remember that the practitioner is ultimately
responsible for the safety and efficacy of any
restoration.

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Conclusion
It is not always possible or feasible to use noble or
precious metals and alloys for fabrication of
restorations. Moreover, most removable partial dentures
are fabricated from chrome-cobalt alloys. Base metal
alloys do have applications in dentistry, though noble
metal alloys are superior in performance. Some patients
may be allergic to some components of the base metal
alloys and care should taken when fabricating such
prostheses.

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References
Phillips Science Of Dental Material 10th & 11th Edition
Restorative Dental Materials – Craig 13th Edition
Dental Materials And Their Selection- 3rd Edition By William J. O'brien
Wataha Jc. Alloys For Prosthodontic Restorations. J Prosthet Dent 2002
Metal-ceramic Alloys In Dentistry: Howard W. Roberts; J Prosthet Dent
Base Metal Alloys Used for Dental Restorations and Implants:
Michael Roach

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