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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.