materials for indirect restoration Flashcards

1
Q

what should the choice of materials facilitate

A

do not remove too much tooth tissue but allow for optimum tooth tissue response

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2
Q

what do we need to be considerate of when removing tooth tissue

A

technical considerations

materials and tissues forming opposing and adjacent contacts

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3
Q

what are the material requirements for indirect restorations

A
thermal expansion
shouldn't attract plaque 
biocompatibility 
accurate fit 
strength - resistance and retention
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4
Q

what are some types of gold and palladium alloys

A
Type III gold alloys 
Silver palladium 
Palladium silver gold 
Gold silver copper palladium 
Palladium copper 
Palladium tin
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5
Q

what are some types of base metal alloys

A

Nickel chromium
Nickel chromium beryllium
Titanium

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6
Q

how do we choose what material to use

A
depending on 
cost 
corrosion 
strength
stiffness 
ductility
hardness
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7
Q

what does the gold colour provide

A
Adds to the colour, 
Adds tarnish resistance
And corrosion resistance
 increases Malleability of an alloy 
Increases density of the alloy
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8
Q

what does the copper add

A

Strengthener
And colour enhancer
Au-Ag-Cu alloys tend to have a reddish colour

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9
Q

what is the role of silver

A

Balance the reddening effect of copper

Silver rich Au-Ag-Cu tend to have a greenish colour

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10
Q

define material biocompatibility

A

The ability of a material to perform with an appropriate host response in a specific application

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11
Q

what are the major drawbacks of use metal alloys

A

controlled casting conditions and of increasing concern biocompatibility

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12
Q

disadvantages with compatibility

A
Grinding and casting fumes
Can lead to conjunctivitis 
Dermatitis 
Bronchitis 
High levels of nickel are carcinogenic 
More commonly nickel is well known to cause contact dermatitis
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13
Q

what might nickel cause

A

contact dermatitis

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14
Q

what is the role of indium

A

In PFM alloys
It strengthens and hardens both gold and palladium
Raises the thermal expansion of both

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15
Q

what does the Griffith equation show

A

the failure stress is = the fracture toughness/ constant x square root fo critical flow size

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16
Q

if we want to increase the failure stress what do we do

A

the critical flaw size

17
Q

why are ceramic better than glass

A

Usually a ceramic consists of a crystalline material in a glassy matrix

If a crack starts to propagate in the class the crystalline domains deviate the propagation

Thus the progression of the crack is hindered

18
Q

which is better ceramic or glass

A

ACC

19
Q

what is our gold standard for aesthetics

A

ceramic

20
Q

what does the addition of alumina do

A

crack stopper prevents cracks propagating through the material increasing the strength

21
Q

what are IPS EMAX crowns made from

A

60% lithium disilicate
Lithium orthophosphate
Core strength of 400Mpa

22
Q

what is the core strength of emax

A

Core strength of 400Mpa