Quiz 2 Review Flashcards
what is the most effecient way to adjust zirconia?
use fine diamonds
the coarsest diamond you want to use is medium
___ or more missing coronal tooth structure warrants a build-up
1/2
what is the most significant factor in long-term success when it comes to teeth restored with build-ups?
amount of coronal tooth structure remaining
___ is a solid transparent plastic made of polymethylmethacrylate
lucite
___ is a white or gray feldspathic mineral composed of potassium and aluminum silicates
leucite
of lucite and leucite, which one has crystals that increase resistance to crack propagation in ceramics, and provide the strengthening component of ceramics?
leucite
which company produces most of the zirconia powder in the world and why is it important to know that?
- Tosoh corp. - they produce 98% of the world’s zirconia
- quality control! it is the purest zirconia
what is transformation toughening?
- a property of zirconia that makes it an ideal material
- when a crack forms in zirconia, a crystalline phase change is induced near the point of the crack, and the zirconia in this area transforms from tetragonal to monoclinic, which takes up the most volume, so the crack doesn’t get any bigger
why is it critical that the abrasive used to adjust zirconia is harder than the zirconia itself?
it doesn’t cause the phase transformation from tetragonal to the other forms - it just cuts the material away instead
what are some things you want to avoid when adjusting zirconia?
don’t apply too much pressure, don’t go too quick, don’t cause too much friction (aka heat)
all of these things can damage the zirconia
what order of abrasives should you use when adjusting zirconia?
start with medium, then fine, then extra fine
which is thinner, accufilm or madame butterfly?
accufilm
of accufilm and madame butterfly, which shows relative intensities?
madame butterfly
of accufilm and madame butterfly, which can give false negatives?
accufilm
of accufilm and madame butterfly, which tends to give better marks in moist environments?
madame butterfly
which material generates the worst marks with articulation ribbon? of accufilm and madame butterfly, which is easier to read on this material?
gold
madame butterfly is easier to read on gold
what order should you adjust a crown/temp?
start with proximal contacts, then esthetics, then margin, then occlusion
how should you adjust proximal contacts?
you want to sneak up on the contact so you don’t overpolish and lose the contact
what are some characteristics of zirconia 3y-tzp?
- yttria partially stabilized
- soft cast
- polycrystalline
- tetragonal zirconia
what are some characteristics of zirconia Ce-TZP/A?
- ceria stabilized tetragonal
- zirconia polycrystalline with alumina nanocomposites
porcelain is a ceramic
zirconia is a ceramic
but ___ is not a ___
zirconia is not a porcelain
describe the 3 zirconia crystalline phases
- cubic = smallest, weakest
- tetragonal = intermediate, strongest, this is the ideal phase
- monoclinic = largest
what is the basic manufacturing process for zirconia?
- hard and soft processing
- partially cintered, green state = soft machining
- remember, green state is larger than the final product because it shrinks when it is cintered, so it needs to be calibrated prior to cintering
- hard machining means fully cintered
what is the basic manufacturing process for lithium disilicate?
pressed and hard machined
what do build-ups do?
- enhance connection to the tooth structure
- minimize amount of restorative material (very important with gold crowns)
- provide thermal insulation
- acts as a chemical barrier
besides the amount of coronal tooth structure remaining, what else correlates with long-term success of indirect restorations?
favorable occlusal scheme in final restoration - this reduces lateral loading and ultimately enhances restorative longevity
why don’t we put pins in all the time?
potential for fracture
greatest potential for iatrogenic failure
we use composite resin as a restorative and foundation material very often. what are some of the disadvantages?
- it shrinks
- higher moisture absorption vs. amalgam
- higher coefficient of thermal expansion
- these disadvantages are pretty much negated though because you can get a very nice restoration using composite resin
if you were doing a build-up in a moist environment, what would be the best material of choice?
zinc-free amalgam
zinc in the amalgam causes it to creep
what margin type can you not use with lithium disilicate?
chamfer
which margin type should you use with gold?
chamfer
what are the advantages of a chamfer margin?
- easy to read
- relatively easy to prepare
- allows a reasonable bulk restorative material
it is easier to put a lip (ski jump) on which type of margin?
rounded shoulder
rounded shoulder margins can be used with any restorative material other than what?
gold or PFM
___ is the only ceramic material where you can get away with a chamfer margin; all other ceramics need more ___
- zirconia
- bulk material
what cement should you use for posts? what cement should you avoid?
- you should use relyx unicem
- avoid glass ionomer cements
