L4 ZIrconia Flashcards
ceramics
man made solid objects formed by baking non-metallic inorganic minerals at high temperatures
zirconia (makeup)
zirconium oxide + yttrium oxide
transformation toughening
tetragonal –> monoclinic
increase in size (3-4%)
types of strength transformation
tensile –> compressive
ability of zirconia to arrest crack propagation by changing its phase at the crack’s edges from _____ to _____. thus, the size of the molecules ____, and ____ stresses are replaced by _____ stresses
tetragonal
monoclinic
increase
tensile
compressive
flexural strength of zirconia compared to enamel + dentin
higher
fracture toughness of zirconia compared to enamel and dentin
higher
why zirconia?
- the widespread use of CAD/CAM
- less expensive and less time consuming (when compared to PFM restorations)
monolithic zirocnia
classified by the amount of yttria
the ENTIRE crown is made of zirconia (no porcelain)
layered zirconia
multiple different layers
the key to classifying dental zirconia is _____
the yttria content
monolithic zirconia 3Y - yttria content
3 mol %
monolithic zirconia 3Y - tetragonal vs cubic
> 85% tetragona
<15% cubic
monolithic zirconia 3Y - strength and translucency
high strength
low translucency
monolithic zirconia 3Y - good to use for…
posterior single unit crowns
FDP
DO NOT USE in highly esthetic areas
monolithic zirconia 3Y - preparation
0.5-0.8mm margin - rounded shoulder or heavy shamfer
0.6mm occlusal reduction (manufacture)
0.7-1mm occlusal reduction (studies)
monolithic zirconia 4Y - yttria content
4 mol%
monolithic zirconia 4Y - tetragonal vs cubic
75% tetragonal
25% cubic
monolithic zirconia 4Y - strength and translucency
lower strength compared to 3Y
acceptable translucency
monolithic zirconia 4Y - good to use for…
single unit restorations (premolar area)
monolithic zirconia 4Y - preparation
0.8-1mm margin
1mm occlusal reduction (manufacture)
1.2mm occlusal reduction (studies)
monolithic zirconia 5Y - yttria content
5 mol%
monolithic zirconia 5Y - tetragonal vs cubic
<50% tetragonal
>50% cubic
monolithic zirconia 5Y - strength and translucency
low strenght
high translucency
monolithic zirconia 5Y - good to use for
anterior crowns
monolithic zirconia 5Y - preparation
1mm margin
1mm occlusal reduction (manufacture)
1.5mm occlusal reduction (studies)
layered zirconia - makeup
porcelain fused to zirconia (PFZ)
core and outer layer of layered zirconia
core = 3 mol% zirconia
outside = porcelain
strength and translucency of layered zirconia
high strength
low translucency
dimensions of core and porcelain (layered zirconia)
0.6mm core
1.2mm (<2mm) porcelain
what happens if there is more than 2m of unsupported porcelain?
porcelain chipping
multi-shade layered zirconia
yttria content is the same throughout
restoration has different shades!
multi-yttria layered zirconia
the yttria content is different throughout
made of same shade
DIFFERENT TRANSLUCENCIES
strength and translucency of multi-yttria layered zirconia
variable strength
variable translucency
because of different yttria contents!
in theory, where should the stronger zirconia go in multi-yttria layered zirconia
stronger phase zirconia at cervical part because it increases fracture resistance
in reality, what happens when the weaker zirconia phase is at the occlusal part?
decreases fracture resistance
when should you use sodium hydroxide in zirconia cementation?
after trying in restoration
when should you use sodium hydroxide in zirconia cementation?
after trying in restoration
why use sodium hydroxide for zirconia cementation?
because zirconia has a high affinity to salivary proteins so cleaning it with sodium hydroxide after the try in is necessary
bonding protocol for zirconia
APC concept
- air abrade
- phosphate monomer
- cement
what kind of cement should be used for zirconia?
dual or self/chemical cure
