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Wrought Dental Alloys
and Dental Wire
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Dental Alloys
Cast Wrought
Dental wireInstruments
Orthodontic bracketsStainless steel crown
Etc.
Fixed partial dentureCrown
Removable partial dentureEtc.
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Wrought Alloys
= alloys that have been worked or shaped andfashioned into a serviceable form for an appliance.
Examples: dental wire, orthodontic brackets, endodonticinstruments, .etc.
Cast
Mechanical work
Wrought
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Microstructure
= fibrous , results from the cold work appliedcuring the shaping operation.
Wrought forms normally have a measurableincrease in tensile strength and hardness butdecrease in ductility and resistance to corrosionwhen compared with corresponding cast
structures.o Results from the entangled, fibrous internal structure
created by the cold work.
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A cast gold alloy Same alloy in wire form
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Wrought forms willrecrystallize during heatingoperations.o The fibrous microstructure is
converted to a grained structuresimilar to the structure of a castform.
Recrystallization results in a
reduction in mechanicalproperties in proportion to theamount of recrystallization.
Fibrous structure
Grained structure
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Fibrous structure
Grained structure
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**Wrought Stainless Steel Alloy
Steel = iron and carbon alloy Stainless Steel = Alloys of iron and
carbon that contain chromium, nickel,manganese, and other metals.
Applications: Orthodontic appliances,
Endodontic instruments, Stainless steelcrown, Denture clasp, etc.
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Stainless steel orthodontic wire
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**Chromium amount must be between 13% and28% for optimal corrosion resistance.
o Cr28% chromium-carbides form embrittle the
steelo Cr resists corrosion well because ofthe formation of a
strongly adherent coating of oxide on the surface
which prevents further reaction with the metal belowthe surface.
o The formation of such oxide layer is calledpassivation.
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Heat treatment above 650oC recrystallization,compositional change, and formation of
chromium-carbides. mechanical propertiesand corrosion resistance.
Stress-relieving treatmentso To remove the effects of cold working during
fabrication and increase ductility 400oC to 500oC for 5 to 120 seconds
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Wrought Cobalt-Chromium-Nickel
Alloy
Elgiloy 40% Co, 20% Cr, 15% Ni, 7% Mo, 2%
Mn, 0.4% Be, 0.15% C, 15.4% Fe, 0.05%other
Applications: orthodontic wire (soft,
ductile, semispring temper, and springtemper)
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Wrought Nickel-Titanium Alloy
Nitinol 55% Ni and 45% Ti High resiliency, limited formability, and thermal memory Shape-Memory Effect: will return to its original shape
when heated from below to above a temperaturetransitional range (TTR).o The term Shape Memory Alloys (SMA) is applied to that group of
metallic materials that demonstrate the ability to return to some
previously defined shape or size when subjected to the appropriatethermal procedure. Generally, these materials can be plasticallydeformed at some relatively low temperature, and upon exposure tosome higher temperature will return to their shape prior to thedeformation.
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Wrought Beta-Titanium Alloy
78% Ti, 11.5% Mo, 6% Zr and 4.5% Sn Can be shaped easily.
Can be soldered and welded.
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