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99 Cards in this Set

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  • Back
The following describes what kind of material?

amorphous, non-crystalline, vitreous, supercooled liquid
glass
A compound of metallic and nonmetallic elements is a ____
ceramic
Which of these is considered metallic?

Si
F
B
K
O
K

(the rest are NON-metallic)
A solid composed of a glassy matrix and one or more crystalline phases produced by controlled nucleation and growth of crystals in glass is called?
glass-ceramic
A ceramic consisting of glass matrix phase and one or more crystalline phases is called what?
porcelain (feldspathic porcelain)
True or False, all porcelains are ceramics, but not all ceramics are porcelains
True
a ceramic composed of a glass matrix and at least 35 vol% Al2O3 is called?
aluminous porcelain
a ceramic formulated to be sintered at cervical area of a metal-ceramic crown to produce an esthetic and a fracture-resistant butt-joint margin is?
shoulder porcelain
Which level of dental porcelains is 1300-1370C?

High-fusing
Medium-fusing
Low-fusing
Ultra-low fusing
high-fusing
Which level of dental porcelains is 1101-1300C?

High-fusing
Medium-fusing
Low-fusing
Ultra-low fusing
medium-fusing
Which level of dental porcelains is 850-1100?

High-fusing
Medium-fusing
Low-fusing
Ultra-low fusing
Low fusing
Which level of dental porcelains is < 850C?

High-fusing
Medium-fusing
Low-fusing
Ultra-low fusing
ultra-low
Which level of dental porcelains is used in porcelain crown and bridges?

High-fusing
Medium-fusing
Low-fusing
Ultra-low fusing
low and ultra low
Which level of dental porcelains is used in prefabricated pontics?

High-fusing
Medium-fusing
Low-fusing
Ultra-low fusing
medium fusing
Which level of dental porcelains is used in denture teeth?

High-fusing
Medium-fusing
Low-fusing
Ultra-low fusing
high fusing
What is the process of fusion of constituent components of a ceramic followed by a rapid COOLING (quenching) of the glass in cold water, resulting in material having extensive CRACKING due to thermal SHOCK?
fritting
What is a frit?
The fine powder that a material is ground into after the fitting process
The benefits of fritting porcelain includes:

(increase/decrease) firing time
(lengthen/shorten) firing cycle
(decrease/increase) drying time
(increase/decrease) shrinkage
decrease, shorten, decrease, decrease
What is the term for when frit is mixed with water or other vehicle and condensed thoroughly into desired shape to obtain dense packing so as to reduce firing shrinkage and porosities; condensation methods used include brush, vibration and spatulation; best condensation possible when powder particles have a range of sizes?
condensation
What is the term for a process of heating closely packed particles to achieve interparticle bonding and sufficient diffusion to decrease surface area or increase density of structure?
Sintering
Sintering is also called what?
firing
True or False, there is no chemical reaction involved in sintering
True
What type of restoration combines the strength and accuracy of cast metal with the esthetics of porcelain?
MCR (metal-ceramic restoration)
What are the three alternate names for an MCR?
Also known as porcelain-fused-to- metal (PFM), porcelain veneer crown (PVC) or porcelain jacket crown (PJC)
True or False, MCRs are stronger than most all-ceramics
True
"keramos" means what?
pottery/potter
What is the chemical formula for silica?
SiO2
What are the 4 isomorphs of silica?
quartz, cristobalite, tridymite (crystalline forms), fused silica (amorphous form, very high melting)
Which of the 4 forms of silica is NOT considered crystalline?
fused silica
What are the three "other" forms of silica?
yellow sand
flint
gem stones
Fill in the blanks:

____ sand - ____ with iron oxide impurities

flint - ______ silica

gem stones - amethyst, ____
yellow sand - quartz with iron oxide impurities

flint - amorphous silica

gem stones - amethyst, opal
2 other uses of silica include:

As a ___ agent

In ___ to provide transparent compound, translucent to ultraviolet radiation, resistant to ____ and ____ shock
drying

glass, thermal, mechanical
Feldspar melts ____ about 1150C to form new solid and liquid
incongruently
What are the three main components of dental porcelain?
Feldspar, glass modifiers, coloring frit and other modifiers
When feldspar is melted, it forms a new solid called ___ and the liquid forms a ___ on cooling
leucite
glass
What is the main difference between potash feldspar and soda feldspar?
potash feldspar has K whereas soda feldspar has Na
What is imbedded in the glassy matrix after feldspar is melted?
leucite
True or False, there is no feldspar left in fired porcelain
True
Feldspar acts as a binding ___ for quartz and clay
flux
When the ___ is sintered to fabricate an MCR, the (higher/lower) fusing powders flow and fuse the mass together
frit, lower
In Latin, flux means what?
flow
___ is fritted with various metal (iodides/oxides/amines) to form the glassy materials that make up dental porcelains
feldspar, oxides
What component of dental porcelain acts to break up silica network and lower firing temp of porcelain?
glass modifiers
Glass modifiers act to break up silica network and lower firing temp of porcelain, which means allow is not heated to temperatures causing ___ (known as flexural creep) of alloy
sag
What is the purpose of the coloring frits in dental porcelain?
create different shades
Frits produced by the addition of metallic oxides are typically what?
coloring frit
For coloring frit, Ni oxide is the color ___ and Co oxide is the color ___
brown, blue
What type of porcelain was originally designed as add on materials (incisal buildup, porcelain margins, repairs, etc.)

high-fusing
medium-fusing
low-fusing
ultra low-fusing
low fusing
What type of porcelain is used for fusing to gold-colored alloys similar to Type IV gold alloys?

high-fusing
medium-fusing
low-fusing
ultra low-fusing
low fusing
What type of porcelain is the newest group and us used as ceramic cores or as veneering ceramics for Ti?

high-fusing
medium-fusing
low-fusing
ultra low-fusing
ultra low-fusing
The oxidation rate of Ti increases markedly above ___C
900
What type of porcelain contains either well-distributed dispersion of small crystal particles, or few to no crystals, depending on whether the ceramic is to be used as veneer or glaze?

high-fusing
medium-fusing
low-fusing
ultra low-fusing
ultra low fusing
What type of porcelain typically has lower enamel wear rate than those produced by conventional low-fusing porcelains?

high-fusing
medium-fusing
low-fusing
ultra low-fusing
ultra low-fusing
What type of porcelain has varying expansion coefficients and may not be thermally compatible with certain ceramic core materials or metal substrates?

high-fusing
medium-fusing
low-fusing
ultra low-fusing
ultra low-fusing
Fill in the blank for the steps in fabricating and MCR:

Fabrication of a metal ___ or substrate

Cleansing metal substrate by __ or __ blasting

____ the metal substrate to prevent the formation of bubbles

Application of ____
coping

air, sand

degrassing

porcelain
The opaque layer of porcelain typically has (light/dark) oxides
dark
What are the three main "layers" in porcelain application?
opaque, body/gingival, incisal/enamel
True or False, each layer of porcelain is condensed and fired separately and in succession
True
What is the point of vacuum firing (or sintering) porcelain?
to reduce the size and number of porosities
When condensed porcelain is places in a porcelain furnace, (liquid/powder) particles are packed together with (water/air) channels around them. As the air pressure is reduced to about __% of atmospheric pressure, air around the particles is also reduced to this pressure.
powder, air, 10%
(continuation of previous question regarding porcelain application)

As the temperature (lowers/rises), particles sinter together and voids (disappear/remain). At temp of ~ __F below the upper firing temp, vacuum is release and pressure inside the furnace increases by a factor of __. Voids are squeezed to ___% of their original size, this reducing the overall volume of porosity by a factor of 10.
rises, remain, 100, 10, 10
Porcelain is supplied as a fine powder that is mixed with ___ or other vehicle and condensed into the desired form
water
Powder particles are of a particular distribution of sizes that produce the (least/most) dense packing when properly condensed
most
Proper and thorough condensation is also crucial in obtaining dense packing of powder particles, which provides two benefits: (higher/lower) firing shrinkage and (more/less) porosities in the fired porcelain
lower, less
Most dental porcelains (are/are not) vacuum fired. Why?
are, to minimize porosities
Why are porosities undesirable?
Reduce translucency of porcelain by scattering light within porcelain which makes it appear more opaque.

Can also lower strength if porosities are extensive
What are the two types of glaze firing?
internal and external glazes
(internal/external) glazes with lower fusing temperature than dental porcelains due to addition of glass modifiers. Stain are tinted/colored glazes
external
(internal/external) glazes produce lifelike results and are not subject to dissolution in oral fluids. However, porcelain has to be stripped completely of color or characterization is unsuitable.
internal
MCR alloy forms ___ during degrassing treatment or initial firing stages (if no degrassing is done)
oxides
What is the link between metal and porcelain in an MCR?
oxides
True or False, oxides are responsible for the bind between metal and porcelain in an MCR
True
What metal elements can be added to noble or high noble alloys to increase formation of oxides for bonding?
In, Ga, Fe, Zn, Sn
Base metal alloys containing Cr, Ni and Be (do/do not) readily form oxides and bond to porcelain, so oxide formation must be carefully controlled
do
True or False, no trace elements are added to BASE metal alloys for oxide formation
True (but they are added to noble and high noble alloys
alphaP is alpha of ___

(alpha = coefficient of thermal expansion)
porcelain
alphaM is alpha of ___

(alpha = coefficient of thermal expansion)
alloy
alpha of porcelain is approximately __ x 10^-6/C so it was RAISED to __ x 10^-6/C by adding what to the porcelain frit?

(alpha = coefficient of thermal expansion)
2-4, 7-8, alkali
alpha of alloy is approximately __ x 10^-6/C so it was LOWERED to __ x 10^-6/C by adding what two metals to Au-containing alloys?

(alpha = coefficient of thermal expansion)
12-14, 7-8, Pt or Pd
Optimum difference is:

(alpha of alloy) > (alpha of porcelain) by __ x 10^.6/C or less

(alpha = coefficient of thermal expansion)
1
Shell and Neilson (1962) determined that spontaneous fracture occurs at __ x 10^-6
1.7
Which of these is NOT thermally compatible under any circumstance?

(alpha of alloy) > (alpha of porcelain)

(alpha of porcelain) > (alpha of alloy)

(alpha = coefficient of thermal expansion)
alpha of porcelain > alpha of alloy is NOT thermally compatible
What are the most common types of failures? (list two)
V (metal oxide-metal oxide) and IV (metal-metal oxide)
Most dental porcelains demonstrate (high/low) hardness values
high
True of False, high hardness means high abrasion potential is inevitable
False
Abrasiveness can be minimized if the surface is ___ or (smooth/rough)
glazed, smooth
(vacuum/non-vacuum) fired dental porcelain can be worked to a very smooth surface for what reason?
vacuum, almost completely free of porosities
True or False, polishing porcelain is at least as effective as glazing in reducing roughness and abrasion potential
True
True or False, fluoride can attack porcelain
True
True or False, acidulated fluorides can etch glass matrix in porcelain
True
What are two examples of fluoride gels that can etch porcelain?
1.23% acidulated phosphate fluoride (APF) and 8% stannous fluoride
What would be considered acceptably low concentrations of stannous and sodium fluoride for us around dental porcelains?
0.4% stannous and 2% sodium
True or False, phosphoric acid has the most destructive effect relative to how long it's applied compared to any other dental acid
False, it has VERY LITTLE EFFECT on dental porcelains!!!
The longevity of MCRs is (worse/better) than all-ceramic restorations
better
All-ceramic restorations have (worse/better) biocompatibility and (more/less) plaque retention than MCRs
better, less
Emergence profiles are less likely to be over-contoured in (all-ceramic/MCRs) restorations
all-ceramic
the cost of all-ceramics is comprable to what type of MCR?
HN
Which has better esthetics, MCR or all-ceramic?
all-ceramic
Fill in the blank for the reasons why all-ceramic restorations are mor esthetic than MCRs:

A (wider/narrower) range of translucency and opacity can be achieved

No masking of metal ___ necessary

No exposed ___ margins are visible

finish lines can be at or slightly below gingival margins, thereby maintaining adequate ___ health and providing acceptable esthetics
wider
oxides
metal
gingival