materials for indirect restoration Flashcards
what should the choice of materials facilitate
do not remove too much tooth tissue but allow for optimum tooth tissue response
what do we need to be considerate of when removing tooth tissue
technical considerations
materials and tissues forming opposing and adjacent contacts
what are the material requirements for indirect restorations
thermal expansion shouldn't attract plaque biocompatibility accurate fit strength - resistance and retention
what are some types of gold and palladium alloys
Type III gold alloys Silver palladium Palladium silver gold Gold silver copper palladium Palladium copper Palladium tin
what are some types of base metal alloys
Nickel chromium
Nickel chromium beryllium
Titanium
how do we choose what material to use
depending on cost corrosion strength stiffness ductility hardness
what does the gold colour provide
Adds to the colour, Adds tarnish resistance And corrosion resistance increases Malleability of an alloy Increases density of the alloy
what does the copper add
Strengthener
And colour enhancer
Au-Ag-Cu alloys tend to have a reddish colour
what is the role of silver
Balance the reddening effect of copper
Silver rich Au-Ag-Cu tend to have a greenish colour
define material biocompatibility
The ability of a material to perform with an appropriate host response in a specific application
what are the major drawbacks of use metal alloys
controlled casting conditions and of increasing concern biocompatibility
disadvantages with compatibility
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
what might nickel cause
contact dermatitis
what is the role of indium
In PFM alloys
It strengthens and hardens both gold and palladium
Raises the thermal expansion of both
what does the Griffith equation show
the failure stress is = the fracture toughness/ constant x square root fo critical flow size
if we want to increase the failure stress what do we do
the critical flaw size
why are ceramic better than glass
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
which is better ceramic or glass
ACC
what is our gold standard for aesthetics
ceramic
what does the addition of alumina do
crack stopper prevents cracks propagating through the material increasing the strength
what are IPS EMAX crowns made from
60% lithium disilicate
Lithium orthophosphate
Core strength of 400Mpa
what is the core strength of emax
Core strength of 400Mpa
