BIOM_ceramics Flashcards
a ceramic is a composed of ______ and _______ elements
metallic and non-metallic –> e.g. oxides, nitrides, silicates
what are the 4 interrelated “key points” that affect materials selection and design. Each affects the other.
structure
properties
processing
applications
properties of ceramics
- very stiff and strong
- brittle
- dense
- insulators of electricity
- refractory: retian strength at high temperatures
- most are opaque
- chemically stable: don’t corrode
ceramics have a (higher or lower) modulus of elasticity
higher –> they are stiffer - after their elastic limit the stress strain curve wains –> there is very little plastic region of the graph - it just breaks - you can’t “bend” it like you can a metal
why are ceramics used very little in dentistry
bc of their lack of toughness - ceramics are too brittle - fracture easy
metals are (more or less) tough than ceramics
more
ceramics are (more or less) biocompatible than metals. WHY?????
more - bc they are already oxidized - they can’t corrode or release ions into their surroundings
in regards to the structure of ceramics - the most important feature to understand their mechanical properties is to know that ceramics form ________ bonds between atoms
ionic
ionic bonds are (more or less) strong than metallic bonds. WHY????
more strong than metallic bond.
- difficult to stretch: higher Modulus of Elasticity
- difficult to break: high strength
what is an ionic bond (what are the electrons doing)
the atoms are TRANSFERRED from one atom to another. marriage analogy.
versus metallic bond where the electrons are promiscuous and free to flow.
true/false. ceramics can be amorphous/glass
true
is it possible for atoms engaged in an ionic bond to form a dislocation?
NO - no plasticity - brittle, once the bonds are broken, once a crack appears…. in grows rapidly and POOF. You’re done.
important things to consider (general principles) when choosing dental materials
durability, efficacy, longevity —–> biocompatability, safety…… slide 10
