Fixed Prosthodontics Materials Flashcards
Porcelain adherence achieved in high noble metal alloys by adding
Tin and indium
Green discoloration caused by
Silver diffusing into sodium ions in porcelain, this is reduced by substituting potassium ions
Which gold alloy is harderst and strongest
ADA type IV
Gold solders are used for
Fixed bridgework
Silver solders are used for
orthodontic appliances
Modifies the orange color of copper
Silver
Increases hardness
Copper
Increases resistance to tarnish and corrosion
Gold
Recommneded distance between parts to be joined should be
0.25mm
A soldering joint should be
Circular in form and occupy region of the contact area
Most important prerequisite of soldering is
Cleanliness
Most common antiflux
Soft graphite pencil
The casting is placed in acidic solution which reduces surface oxides
Pickling
Fe(iron) is key in
PFM bonding to gold based alloys
Chromium is key in
PFM bonding to gold substitute alloys
What is predominant mechanism in metal ceramic bond
Chemical form of attachment
When materials heated to form glassy mass and. Then rapidly cooled to fracture them into many small fragments is called
Frit
What are glass modifiers in porcelain
Potassium and sodium
Most formulations of porcelain consists of
Low fusing glass frit and high expansion frit
Devitrification occurs if
Ceramic is fired too often
What happens to porcelain after firing
Volumetric shrinkage
Which porcelain masks the darkness of metal oxide
Opaque porcelain
Milky state of porcelain
Because of devitrification and it makes glazing difficult
Most PFM failures because of
Built in stresses in porcelain
