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olola's version from 2016-09-19 10:05

rank from highest to lowest (Acrylic, Dentin, Enamel, Amalgam)

Question Answer
Material KHN (hardness)Enamel (343) > Amalgam (110) > Dentin (68) > Acrylic (20)
Elastic ModuliEnamel (48k) > Amalgam & Dentin (both 13.8k) > Acrylic (2.4k)
Compressive StrengthAmalgam (400) > Enamel & Dentin (both 275) > Acrylic (83)
Tensile StrengthDentin (60) > Amalgam (48) > Enamel (35) > Acrylic (21)
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what function does this serve in denture base fabrication

Question Answer
GlycoldimethacrylateCross-linker
Hydroquinoneinhibitor (increase shelf life)
Tertiary AmineChemical cure initiator (only if chemically cured)
PMMA beadsfiller
MMA monomerthe actual polymerization reaction happening that creates the acrylic resin
Sodium Alginate(tin foil substitute) prevents acrylic from bonding with master cast
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unsorted

Question Answer
Rank tooth structure, porcelain, amalgam and PMMA from highest to lowest in terms of coefficient of thermal expansionPMMA > amalgam > porcelain > tooth
the _____ (higher/lower) the coefficient of thermal expansion, the greater the amount of expansion and contraction for a given temperature changeHigher
As a result of it high coefficient of thermal expansion, _____ is not considered as a definitive restorative material, although it was used as such at one time.PMMA
What filler is used during denture fabrication?PMMA (reduces volumetric shrinkage to 5-6% by volume)
This polymer acts to displace monomer and becomes interlocked in the newly formed denture-base matrix, increasing mechanical strength and decreasing its volumetric shrinkagePMMA
PMMA powder is the filler used with _____ liquid monomer for denture base fabricationMMA
To prevent the resin from adhering to the gypsum mold, ____ ____ ____, an alginate material, is used.tin foil substitute
If this layer were not present when processing dentures. the processed denture could not be removed from the master castSodium alginate (tin foil substitute)
list the 4 stages (in order) that acrylic goes through in heat and chemical cure compression moulding denture fabricationSandy, Stingy/Sticky, Doughy, Rubbery
What happens if the denture flask is packed too soon? (before right amount of set)(if before doughy; i.e. during stringy/sticky) then monomer will remain in localized pockets instead of uniformly spread out, producing localized shrinkage porosity
What happens if the denture flask is packed too late? (after appropriate stage of set)(The material will not compress as easily) excessive vertical dimension if packed at this late stage (if packed during Rubbery stage)
T/F: The cured denture base would ideally shrink at the same rate as the gypsum mold when the processing cycle is completed, and this rate of shrinkage is much lower than that of the resin.True
T/F: The cured denture base would ideally shrink at a slower rate than the gypsum mold when the processing cycle is completed, and this rate of shrinkage is much lower than that of the resin.False (must shrink at same rate)
T/F: The cured denture base would ideally shrink at the same rate as the gypsum mold when the processing cycle is completed, and this rate of shrinkage is much higher than that of the resin.False (much lower than that of resin)
As the flask cools, the denture locks in a high degree of ______ ______.residual stress
What is the biggest clinical implication of Residual Stress locked into denture bases as a result of differing thermal contraction between acrylic and master cast as the flask cools?Polishing (heat from friction) and Cleaning with dentures with heat can cause them to warp (causing sore spots or poor fit)
Heat-curing denture flasks should be placed in 65 deg C water for 90 minutes to cure the _____ (thick/thin) sections and then 100 deg C water for 1 hour to cure _____ (thick/thin) sections65 thick; 100 thin
After _____ hours immersed in 65 deg C water, the thick sections of heat-curing denture bases are as converted as they will be1.5 hours
Theoretically, dentures of uniform thickness would not need a ramped temperature processing cycle when heat curingTrue
If heat-curing dentures, and skipping the first step at 65 C (going straight to boiling water) then what would the resultGreater porosity and lower strength (boiling off monomer)
What is the ideal way to repair broken heat-cured denture?heat-cure repair in denture flask
T/F: Repair resins only adhere to the existing denture base by micro-mechanical. means, not by covalent bonding.True
T/F: repair resins adhere to the existing denture base by covalent bondingFalse
T/F: Areas in need of denture repair should be modified because resins do not covalently bond to denture baseTrue
T/F: Areas in need of denture repair do not require modification for mechanical retention, because repair resins bond covalently to denture baseFalse
What is the alternative choice of material for denture fabrication when a patient has an allergy to methacrylates?Polycarbonate (expensive and hard to make)
these materials temporarily cushion irritated tissues to get them into a healthy state prior to the final denture impressionTissue conditioners
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comparing types of denture fab processes

Question Answer
what type of denture fabrication (Fluid-pour, Heat-cured, Chemically-cured) has the lowest residual monomerHeat-cured
what type of denture fabrication (Fluid-pour, Heat-cured, Chemically-cured) necessitate the need for spruesFluid-pour
Do Heat-cured or Chemically-cured dentures have greater residual free monomer?Chemically cured has more (but Fluid pour has most)
Do heat-cured or chemically-cured dentures have more shrinkageHeat-cured has slightly more shrinkage
For which type of denture fabrication (Fluid-pour, Heat-cured, Chemically-cured) do different parts of the denture polymerize at different rates depending on thickness?Heat-cured
what type of denture fabrication (Fluid-pour, Heat-cured, Chemically-cured) has disadvantages of air bubbles and voids in the denture base, shifting of the teeth, increased incidence of "pop-out" of acrylic teeth, decrease of vertical dimension, and higher polymerization shrinkageFluid-pour
What type of cleaners should not be used on lab-cured silicon denture reliners?those with Hypochlorite (because will dissolve adhesive that holds reliner on)
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what are the disadvantages of this type of base compared to acrylic denture bases

Question Answer
Butadiene-styrene rubber-reinforced acryliclower color stability, higher solubility and water sorption (what even does that mean)
Polycarbonateexpensive and difficult to make (must be injection molded at high temperature and pressure.)
Vinyl Resindifficult to make, and increased chance of fracture (greater residual stress)
Metal Denture baserelining not possible (requiring entirely new fabrication after ridge resorbs over time)
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what are the advantages of this type of base compared to acrylic denture bases

Question Answer
Butadiene-styrene rubber-reinforced acrylicless likely to break (harder? less brittle?)
PolycarbonateHigher impact strength, less water sorption
Metal Denture basebetter fit (greater accuracy of lost-wax process), preferable conduction of heat to soft tissue (more like its not there in this respect)
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disadvantages of materials for re-lining or re-basing a denture base

Question Answer
mouth cured-acrylic relinerporous, poorly bonded to denture base, high residual free monomer
Lab-cured acrylic relinersrisk of changing occlusion or warping denture
Soft acrylic relinersbecomes stiffer and less flexible (due to water sorption and plasticizer leaching)
Lab-cured silicon relinerssilicon can grow yeast (candidiasis) & adhesion to denture base is not permanent b/c requires adhesive
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