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Metallurgy
The technique or science of working or heating metals so as to give them certain desired shapes or properties
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______ is the oldest restorative material
Metal
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Alloy is a
mixture of two or more metals
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Properties and function of metals are explained by the _______ of all metals
Crystalline structure
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________ perfects an accurate casting procedure for dental restoration using gold
William H. Taggart
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In the 1930’s four types of gold alloy were developed what were they used for
- Type I soft for inlays
- Type II medium for onlays and crowns
- Type III (hard) for onlays, crowns and bridges
- Type IV extra hard for partial dentures
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The gold content of an alloy is described in two ways
Karat and Fineness
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24K gold is how much fineness and what percentage of pure gold
1000 fine= 100% pure gold
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18K gold is how much fineness and what percentage of pure gold
750 fine= 75% pure gold
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12K gold is how much fineness and what percentage of pure gold
500 fine= 50% gold
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Noble metals are _____ and include _____
- Inert or non-reactive
- Gold Platinum Palladium Iridium Ruthenium Osmium
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noble metals were formerly known as
precious metals
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Base metals have
increased stiffness, strength, and oxide formation (which is critical for veneering the porcelain onto the metal surface).
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Base metals include
Nickel Chromium Beryllium Molybdenum
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For materials to be considered High Noble Alloys what is required
Noble Metal Content of at least 60% with gold content of at least 40%
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For materials to be considered titanium and titanium Alloys what is required
Titanium content of at least 85%
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For materials to be considered noble Alloys what is required
Noble Metal Content of at least 25%
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For materials to be considered Predominantly Base Alloys what is required
Noble Metal Content 25% or less
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Porcelain is esthetic but
lacks shear and tensile strength to stand alone in most restorations
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_______ were the most sophisticated material of the Stone Age and they have been important ever since
Ceramics
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For dental purposes their properties are
- Low thermal conductivity
- Low electrical conductivity
- High compressive strength to resist wear Exceptional esthetics and light reflection. Low shear strength (brittle material) which makes their use in posterior a challenge
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Ceramics are materials composed of
metallic oxide compounds like feldspar, quartz, and clay
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Porcelain is ______ and is made of ______
- ceramic
- feldspar, quartz, kaolin and Lucite
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What is the purpose of the feldspar in porcelain
the bulk of the material
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What is the purpose of the kaolin in porcelain
opacifier that makes mass more workable
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What is the purpose of the Lucite in porcelain
a crystalline material that strengthens the mass and makes it more useful in stress bearing areas
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What was the original use for porcelain
porcelain jacket crown
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because the porcelain jacket crown was limited it led to the ___ technique
- veneering
- a strong metal coping with a very esthetic porcelain
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What is high fusing and what is it used for
1300-1350 degrees C. Used for denture teeth
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What is low fusing and what is it used for
850 – 1050 degrees C. Used to veneer metal in PFM’s
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What is medium fusing and what is it used for
1100-1250 degrees C. Used in anterior porcelain jacket crowns (the old style)
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The most useful all ceramic crown is the
all zirconia crown
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E-MAX is a strong ceramic called
lithium disilicate
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To repair fractured porcelain a chemical etch with a strong acid solution such as _______ is required and a ______ bonding agent
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