Dental Ceramics Flashcards
What are the 2 main differences in composition between decorative and dental ceramics?
Decorative ceramic contains more KAOLIN then dental.
Dental ceramic contains glass which decorative does not.
Why do you make conventional dental ceramic crowns too big?
Have to make them roughly 20% bigger - upon setting it shrinks by roughly 20% = called SINTERING
What is sintering and what leads to it?
Sintering is the shrinkage of ceramics upon setting - coalesces into a single harder piece of ceramic.
Heating leads to this
What are the properties of conventional dental ceramics (excluding mechanical)?
Aesthetic
Very chemically stable
Good biocompatibility
Thermal properties - similar to tooth substances. Similar thermal expansion co-efficient to dentine
Dimensionally stable - ONCE FULLY FIRED.
What are the mechanical properties of dental ceramics?
High compressive strength
High hardness
Low tensile strength
Low flexural strength
Low fracture toughness
What are some of the problems with dental ceramics?
Static fatigue - time dependant decrease in strength even in absence of any applied load.
Surface micro-cracks - can occur during manufacture, finishing or occlusal wear.
Slow crack growth - cyclic fatigue under occlusal forces in a wet environment over time
Not suitable for bruxist’s due to brittleness
How can you modify ceramic surface to make it more retentive prior to using silane?
Treat surface with 10% hydrofluoric acid
Chemically how does a silane coupling agent work when bonding composite to ceramic?
One end of silane forms strong bond with the oxide groups of the ceramic the other end has carbon double bond that interacts with the composite resin
What is the definition of opalescence?
Shade of the colour
How do you make a conventional ceramic stronger?
Produce a strong coping
What is the benefit of using an aluminia core in ceramics?
Increases fracture toughness - cracks cannot propagate through the material as easily due to large aluminia particles
How are dental ceramics made translucent?
Removal of kaolin (clay)
Feldspar and silica replace it
