metal ceramics and crowns with labial porcelain margins Flashcards
what is a ceramic
A product made from a non-metallic inorganic material processed by firing at a high temp to achieve desirabled properties
what are the groups of dental ceramics
High fusion
MEdium Low fusion
Ultra low fusion
temp for high fusion ceramics
1290-1370 degrees C
temp for medium fusion ceramics
1090-1260 degrees C
temp for low funsions ceramics
870-1070
temp for ultra low fusion ceramics
less than 850
what dental ceramics are used for Dnture teeth and porcelain jacket crowns
High fusion
Medium fusion
what dental ceramics are used for metal-ceramic crowns
Low fusion
Ultra Low-fusion
what is feldspar made of
A naturally occuring glass with silicas, fluxes, and alumina neatly bound together
what does feldspar bind
all 3 forms of clay bodies together once fused at a high temp
how is Frit mad
materials of dental porcelain are heated to a high temp then cooled fast to cause glass to fracture
what are the chemicals of Feldspar
Potassium aluminum silicate orthoclase
Sodium aluminum silicate albite
what is the chemical in quartz
Silicon oxide
what is vitrification
Turning cystalline silica along with associated fluxes and modifiers into glass
what does porcealin turn into after vitrification
Ceramic body
what is the ceramic body made of
the refractory skeletal structure
feldspathic glass betwen the refractory particles
how is the refractory skeletal structure made in a ceramic body
through sintering and fusing processses to help it maintain shape
how is porcelain different than glass
Glass with a refractory internal structure
do all porcelains have the same composition
No, have different ratios
what are the types of dental porcelains for an MCC
Opaque porcelain
Body/dental porcelain
Incisal/enamel porcelain
what does the opaque porcealin contain
Opacifying oxides
can you see through body porcelain
Yes, it is translucent
what is found in body porcelain
metalic oxides that give shade or base color selected
how see through is the incisal/enamel porcelain
More translucent than body
what are the dental porcelains mixed with
Water based glycerin continaing liqued
how should enamel porcelain be added
over build it
how should grind porcelain
Use stones or diamond burs only used to grind porcelain on a low speed
how should shimstock feel when contact is good
Should drag when crown is seated, but if it holds it is too tight
what wheels are used to adjust contact
Blue: course
Pink: medium
Gray: fine
how to prep porcelain for a second bake
Clean in DI for 10 min
add porcelain to areas that are deficient
advantage of Porcelain labial margin
Improve esthetics
Less plaque retention
disadvantages of porcelain labial margin
- Generally inferior margin adaptation compared to cast metal
- decreased strength compared to metal
- more time consuming
- slight more expesnive than conventional MCC
what are the techniques for porcelain labial margin fab
Platinum foil matrix tech
Porcelain wax technique
Direct lift technique
what is the direct lift technique
Apply shoulder porcelain on margin and dry with tissue paper and brush excess with large brush
advantage of direct lift technique
LEast time consuming
disadvantage of direct lift technique
Shoulder porcelain needed
Slightly rough margins
when were porcelain crowns first used
1903 ( over 100 yeras ago)
what is the problem with cooling porcelain
causes the metal to distort ( low temp is desired)
what chem is the major component of porcelain
SiO2
why should you overbuild porcelain
account for voids
Shrinks 45-30%
what color should shoulder porcelain be
should be opaque
what holds more plaque, ceramic or metal retainers
metal
what technique is generally used to pain porcelain on the margin
Direct lift technique
