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134 Cards in this Set
- Front
- Back
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what is an amorphous, non-crystalline, vitreous, supercooled liquid
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glass
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ceramics are made up of metallic (Al, Ca, Li, Mg, Na, Sn, Ti, Zr) and nonmetallic (Si, F, B, O) elements T/F
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true
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a glass-ceramic is a solid composed of a glassy matrix and one or more crystalline phases produced and controlled by what
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nucleation and growth of crystals in glass
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what is a specific type of ceramic consisting of glass matrix phase and one or more crystalline phases (such as leucite, K20*AL203*4Si02)
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porcelain(feldspathic porcelain)
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all ceramics are porcelains but not all porcelains are ceramics T/F
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false, all porcelains are ceramics, but not all ceramics are porcelains
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what type of porceli is a ceramic composed of a glass matrix phase and at least 35 vol% AL2O3
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aluminous porcelain
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what type of porcelain is a ceramic formulated to be sintered at cervical area of a metal-ceramic crown to produce an esthetic and fracture-resistant butt-joint margin
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shoulder porcelain
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what is the term for the fusion of constituent components of a ceramic followed by rapid cooling (quenching) of the glass in cold water, resulting in a material having extensive cracking due to thermal shock
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fritting
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what is done to produce frit
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after fritting te material is then ground to fine powder
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what are the benefits of fritting porcelain
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decreases firing time, shortens firing cycle, decreases drying time, and decreases shrinkage
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when frit is mixed with water or other vehicle and compressed thoroughly into desired shape to obtain dense packing it is known as what
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condensation
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what is the purpose of condensation of frit
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reduces firing shrinkage and porosities
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what are the 3 types of condensation methods for condensing frit
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brush, vibration and spatulation
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condensation is best when what is true
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when powder particles have a range of size
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what is the process of heating closely packed particles to achieve interparticle bonding and sufficient diffusion to decrease surface area or increase density of structure
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sintering or firing
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what classification of dental porcelain has a fusing temperature of 1300-1370 C, and is used in denture teeth
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high-fusing dental porcelains
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what classificaiton of dental porcelains have a fusing temperature below 850 C and is used in porcelain crowns/bridges
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ultra-low fusing dental porcelains
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what classification of dental porcelains has a fusion temperature between 1101-1300 C, used in prefabricated pontics
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medium-fusing dental porcelains
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what classification of dental porcelains has a fusion temperature range of 850-1100 C, and is used in porcelain crowns and bridges
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low-fusing dental porcelains
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what are the 4 isomorphs of silica
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quartz, cristobalite, tridymite (crystalline forms), and fused silica (amorphous form, with very high melting)
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what 3 isomorphs of silica are crystalline isomorphs of silica
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cristobalite (cubic or tetragonal crystals), tridymite (rhombic crystals), and quartz (hexagonal crystals)
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alpha quartz has a fusion temperature of what and is used in what
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below 575 C and is used in casting investments
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beta quartz has a fusion temperature of what and is used in what
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above 575 C and is used in casting investments
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quartz is transformed into what above 870 C
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tridymite
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quartz is transformed into what above 1470 C
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cristobalite and is used in casting investments
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what is the amorphous isomorph of silica
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fused silica
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yellow sand is a common form of silica that has what components
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quartz with iron oxide impurities
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flint is common form of silica that is made up of what
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amorphous silica
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gem stones are types of silica T/F
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true
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silica can be used in glass to provide a transparent comound, translucent to uv radiation, resistant to thermal and mechanical shock and as a drying agent T/F
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true
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feldspar porcelain can be what two types and what are their formulas
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potash feldspar (K20*AL2O3*6SiO2) and soda feldspar (Na2O*Al2O3*6SiO2)
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feldspar melts incongruently above 1150 C to form what new solid and liquid
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leucite is the new solid, and the liquid forms glass on cooling
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how much feldspar is left in fired porecelain
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none
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feldspar serves as what for quartz and clay
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binding flux, when the frit is sintered to fabricate an MCR, the lower fusing powders flow and fuse the mass together. these lower melting powders are said to act as fluxes
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what are the 3 general components of dental porcelain
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feldspar, glass modifiers, and coloring frits and other modifiers
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what is the purpose of the glass modifier in the dental porcelain
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breaks up silica network and lower firing termpature of porcelain, which means alloy is not heated to temperature causing sag of alloy
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glass becomes more prone to what with increasing amounts of glass modifier
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chemical attack
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what are coloring frits made of
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metallic oxides such as nickel oxide for brown, cobalt oxide for blue, etc
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what are the steps in fabrication of an MCR
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fabrication of metal coping or substrate, cleansing metal substrate by air-blasting or sand-blasting, degassing the metal substrate to prevent formation of bubbles, and porcelain application
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what are the 3 layers in porcelain (after or during condensation and firing?)
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opaque layer, body/gingival layer, and incisal enamel layer
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each layer of porcelain is condensed and fired together T/F
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false, each layer is condensed and fired seperately and in succession
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what is the purpose of vacuum firing porcelain
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reduce size and number of porosities
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when firing porcelain: at tempeature of 100 F below the firing temperature the vacuum is released and pressure inside the furnace increases by a factor of 10. what does this do
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voids are squeezed to 1/10th of their original size, thus reducing he overall volume of porosity by a factor of 10
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proper and thorough condensation of porcelain components provides what 2 benefits
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lower firing shrinkage and less porosity in the firec porcelain
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why are porosities in porcelain undesirable
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they reduce translucency of the porcelain, and scatter light within the porcelain, which makes it appear more opaque (if porosities are big it can lower strength of porcelain)
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external glazes with higher fusing temperature than dental porcelains due to addition of glass modifiers T/F
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false. lower fusing temperature
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internal glazes have what pros and cons
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produce lifelike results and are not subject to dissolution in oral fluids, but the porcelain has to be completely stripped if color or charictarization is unsuitable
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what types of bonds are involved with porcelain metal bonding
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van der waals forces, mechanical entrapment, compressive forces, and chemical bonding
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how is van der waals forces important to porcelain metal bonding
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minor contributor to overall strength , but are important for initiation of chemical bond
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what is mechanical entrapment associated with porcelain-metal bonding
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it is the interaction between porcelain and microabrasions in alloy surface produced by air abrasion or finishing abrasives
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what is the major contributor to overall bond strength in porcelain-metal bonding
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chemical bonding
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MCR alloys form what during degassing tx or initial firing stages. this is the link between metal and porcelain, and is responsible for dev't of a bond
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oxides
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what is added in trace amounts to noble and high noble alloys to increase the formation of oxides for bonding
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In, Ga, Fe, Zn, or Sn
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base metal alloys containing what readily form oxides and bond to porcelain
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Cr, Ni, and Be
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the addition of what to base metal alloys resultsin oxide layers that improve adherence
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yttrium
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are trace elements added to base metal alloys for oxide formation
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no
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coefficient of thermal expansion for porcelain is what. what is added to bring this up, and what value does it bring it up to
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2-4 X 10^-6/degree C. alkali is added to bring the coefficient of thermal expansion up to 7-8 x 10^-6/degree C
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coefficient of thermal expansion for alloy is what? what is added to bring this number down and what does it bring it down to?
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12-14 x 10^-6/degree C, Pt or Pd to Au-containing alloys is added to lower the coefficient to 7-8 x 10^-6/ degree C
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the optimun difference between the coefficient of thermal expansion for alloy and porcelain is what
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1 x 10-6/degree C or less
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if difference in coefficient of thermal expansion is 1.7 x 10^-6 or greater what occurs
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spontaneous fracture
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what is the most common type of interface failure between porcelain and alloy
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type 4
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what are the types of porcelain-metal bond failure 1-6
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1: between metal and porcelain, 2: between metal oxide and porcelain, 3: cohesive failure within porcelain, 4: between metal and metal oxide, 5: between metal oxide and metal oxide, 6: cohesive failure within metal
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most dental porcelains have what hardness value? does this mean that high abrasion potential is inevitable
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no
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abrasiveness can be minimized how
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if the surface is glazed or polished smooth
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what effect can fluoride have on porcelain
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can attack porcelain. topical fluoride gels etch the glass matrix within minutes, creating a rough, dull surface
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what types of fluoride can etch porcelain
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1.23% acidulated phosphate fluoride or 8% stannous fluoride
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what effect does phosphoric acid, used regularly in dentistry for the acid etch procedure have on porcelain
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little to no effect on dental porcelain
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a glassy matrix containing one or more crystalline phases produced by controlled nucleation and growth of crystals in glass is called what
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glass-ceramic
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what type of dental ceramic is used to provide a strong base onto which a body ceramic is veneered
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core ceramic
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what type of ceramic contains sufficient Al2O3 for strength
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alumina core
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what is a dental ceramic that is specially formulated to be cast using the lost wax technique
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castable ceramic
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what is a process using heat and pressure to mold the ceramic into a predetermined shape
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injection molding
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what is the term for MgAl2O4 used as a core material
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spinel or spinelle
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which of the following properties is NOT correct concerning ceramics: esthetic, biocompatible, chemically instable, thermal conductivity and coefficient of thermal expansion similar to enamel AND dentin, brittle, non-abrisive, and low fracture toughness and tensile strength
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it IS chemically stable, it IS abrasive
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feldspathic porcelain, leucite-reinforced porcelain, glass ceramic, and all-ceramic are the different types of ceramics T/F
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true
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what are the methods for processing ceramic materials
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sintering, machining, copy-milling, casting, pressure-molding, and CAD-CAM
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what is a stress that is focused at tips of small surface flaws and defects
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stress concentration
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what is a stress that propagates a crack through material
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crack propagation
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how do tensile forces and compressive forces affect brittle materials
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tensile forces tend to pull cracks open, where as compressive forces tend to hold cracks and surface flaws closed
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what are methods for strengthening brittle materials
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surface smoothing, introducing residual surface compressive stress, and interruption of crack propagation
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what are the 3 possible methods of introducing residual surface compressive stresses
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ion exchange, thermal tempering, and thermal expansion mismatch
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how is ion exchange introduction of surface compressive stress accomplished
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by placing a glass article containing sodium in a bath of molten potassium nitrate. because potassium is larger than Na, they must squeeze into sites that are too small and thus they exert stress on the surrounding glass and create compressive stress in the surface layer
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how does thermal tempering introduce residual surface compressive sresses
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the outer skin of molten glass is frozen by jets of air. then when the inner core solidifies, it pulls on the outer skin, creating the compressive stress.
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how does thermal expansion mismatch introduce compressive stresses into the surface layer
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an inner layer of a higher thermal expansion glass is sandwiched between two layers of a lower expansion glass, and allowed to cool.
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what are the 3 types of dispersions used to interrupt crack propagation
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tough crystalline phase (dicor, aluminous porcelain PJCs), particle-matrix thermal expansion coefficient mismatch (MCR porcelains, Optec and IPS Empress), and transformation toughening (partially stabilized zirconia)
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failure of ceramic restorations are found to occur most commonly where
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at sharp internal line angles on coping and at areas of inadequate tooth reduction
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tooth reduction when using a ceramic restoration should be how much axially and occlusally
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1-1.5 mm axially and 2 mm occlusally
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what advantages areprovided by aluminous porcelain crowns and how
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a tin oxide coating is electroplated on Pt foil and they form a bond with porcelain resulting in a restoration with reduced subsurface porosity and fewer microcracks.
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how is the survival rate for aluminous porcelain crowns in anteriors and posteriors
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anteriors have excellent survival rate and in posterior teeth it has a moderate survival rate
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what is the strongest all-ceramic material, that can be used as a single unit crown for anterior and posterior teeth, and 3 unit fixed partial dentures with pontic spanning up to 14 mm
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in-ceram zirconia
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how does the flexural strength, opacity, and fracture toughness of alumina compare to zirconia
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zirconia has double flexural strength and fracture toughness and is also more opaque than alumina. for these reasons zirconia is more suited for use in posteriors
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what types of cements can be used in placing in-ceram zirconia
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GI or resin cements, but not compomers and zinc phosphate cements (due to water sorption, expansion and subsequent failure)
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what type of ceramic is heat-pressed, injection-molded and uses lost wax process. it contains 40-50 % leucite-reinforced feldspathic porcelain, and canbe used for single unit anterior and posterior crowns, inlays, onlays, and veneers
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IPS Empress
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what type of ceramic contains lithium disilicate and lithium orthophosphate in a translucent, porous framework that is infiltrated with a sintered fluorapatite glass-ceramic.
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IPS Empress 2
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what is IPS Empress 2 used for
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full coverage crowns and 3-unit fixed partial dentures up to the 2nd premolar
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how does IPS Empress 2 compare to IPS Empress
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IPS E2 is 3 times stronger, shows lower wear on opposing teeth and has a better fit
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what type of cement is used to place IPS Empress 2
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use hybrid ionomer cement having less than .5 % linear expansion if conventional cementation technique selected
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what is CEREC
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CAD/CAM using ceramic blocks, that uses 2-D intraoral scan of the prepped tooth before milling. can be used to fabricate anterior and posterior crowns, inlays, onlays, and veneers
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what does CAD/CAM stand for
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Computer-Aided Design, Computer Aided Machining
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what all ceramic material claims to have one of the highest flexural strengths, can be used for single unit crowns for anterior and posterior teeth only, uses CAD/CAM scan of master die which is sent in digital format to a manufacturer
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procera allceram
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what all ceramic material has the strength, reliability and biocompatability of zirconia and the accuracy, control and advanced materials of CAM process.
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cercon
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what all ceramic material is actually a class of porcelain, originally designed as add-on material
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low fusing porcelains
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what is the definition of biocompatible
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harmonious with life and not having toxic or injurious effects on biologic function
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what is any substance, other than a drug, that can be used as part of a system to treat, augment or replace any tissue, organ or fxn of the body
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biomaterial
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when would you see an inert material
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never. it is not feasible because a response will occur, you want a response that is acceptable
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adverse reactions reported from patients to all classes of dental materials, especially what 3 findings
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hypersensitivity, contact sensitivity, and estrogenicity
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contact sensitivity to latex resins, HEMA, TEGDMA, and camphoroquinone are very common to the dental team T/F
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true
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what is defined as a substance that is not irritating on first exposure but produces reactions on subsequent exposure to similar concentrations
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allergen
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what is defined as an inflammatory response brought about without intervention of an antibody or immune system
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irritation
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what is defined as an inflammatory response requiring participation of an antibody system specific for the allergenic material
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sensitization
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what is an organic compound that is not a normal component of the organism
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xenobiotic molecule
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what are the tiers of biocompatability testing
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tier 1(in vitro tests), tier 2 (animal tests), and tier 3 (usage tests)
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tier 2 tests are tests done in an animal that are usage tests T/F
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FALSE: they are done on animals bur are not usage tests
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tier 3 is when the material is in use in human volunteers T/F
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true
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fill in the blanks for advantages and disadvantages for 1,2, and 3
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in biocompatability testing what would a score of 0, or +1, or +2 indicate
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0 indicates safety, 1 indicates moderate reaction , 2 indicates dangerous to cells tested
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dental materials are considered what by the FDA? what does this mean to testing?
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they are considered devices. during testing only need to show safety and efficacy
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the amount of a specific agent released from a material is always proportional to the amount present in the material T/F
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False, it is not proportional to the amount present in the material
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toxicity is dose dependant and proportional to the amount T/F
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true
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what allergic response is acute anaphylactic and what response is a delayed or cell mediated hypersensitivity
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type 1 is anaphylactic, type 4 is delayed or cell mediated hypersensitivity
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what would a mutagenic effect cause
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a change in DNA sequence
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what percentage of crowns/partials contain Ni in the US
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33%
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what is the toxicology fo Ni
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toxic in high concentration, potent allergen, known carcinogen in some forms
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what are the 3 forms of mercury
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elemental, inorganic ion, and organic
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place the types of mercury in order from most toxic to least toxic
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organic, elemental, inorganic
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how is elemental merucry absorbed
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via skin or inhalation as vapor
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how is organic mercury absorbed
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absorbed by gut
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what is the half life of mercury in the body
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20-90 days
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what is the most common occupational disease for dental workers
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allergic contact dermatitis
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allergic contact dermatitis is a reaction to what compounds
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bonding agent monomers, latex products, acrylc components of dental cements, and polyethers (independant of dose for all of these)
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what is the most common adverse reaction to dental material
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allergic contact stomatitis
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what is allergic contact stomatitis typically a reaction to
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Cr, Co, Hg, eugenol, components of resins, and formaldehyde
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what is the ability of chemicals from the env't known as xenoestrogens to mimic the effect of human estrogen
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estrogenicity
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what compound was hypothesized to be a xenoestrogen but was not found to be released from sealants or restorative resins
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bisphenol A
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