DMS Flashcards
What do you fuse porcelain with to reduce the chances of fracture?
Metal alloys
What is the key property of porcelain that makes it a poor material to use and why does it need the support of a metal alloy?
It is extremely brittle
What are the four ideal mechanical properties which metal alloys process and their opposites?
Hard - soft
Ridgid - flexible
Ductile - brittle
Strong - Weak
Define stress?
The amount of force exerted on an object.
Define strain?
The amount of deformation experienced by a body.
Describe the difference between a brittle material and ductile material. Reference the stress-strain graph.
A brittle material fractures very quickly once the elastic limit is reached.
A ductile material allows for much more bending and changing of shape
Define hardness?
Resistance to surface indentation
What does elastic modulus indicate about a material?
How ridgid it is.
Want a high EM/YM
What are the 3 things that make up a porcelain metal restoration?
Porcelain
Metal oxide
alloy
When matching porcelain to alloy what property should you consider?
The thermal expansion co-efficient
The MP (Due to creep)
How rigid it is, reduce brittleness.
What are the 3 ways in which porcelain bonds to alloy?
Mechanical
Stressed skin
Chemical
Define stressed skin in terms of bonding?
Due to slight differences in the thermal expansion coefficient. The alloy grips onto porcelain during the cooling stage
Describe how porcelain and metal bond chemically?
The metal oxide layer and porcelain share electrons during the furnace stage
When is the metal oxide layer created?
Furnace stage
