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80 Cards in this Set
- Front
- Back
This is the measure of the body's response to a specific material.
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Biocompatibility
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What are some possible reactions to dental materials?
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Chemical irritation
Unpleasant tastes Localized rxn Generalized rxns Cytotoxicity Inflammatory rxn |
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This is the percent shrinkage or expansion of a material due to a chemical reaction.
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Dimensional change (expressed as a percentage)
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Linear thermal expansions is expressed as...
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...coefficient of thermal expansion.
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What is percolation?
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Contraction of restoration due to cool temperature. When the temperature returns to normal the fluid is forced out of the space.
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Materials with high conductivity are ________ conductors of heat and cold.
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good
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What is galvanism?
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Generation of electrical currents that the patient can feel.
Comes from the presence of dissimilar metals in the mouth. |
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This is the dissolution of metals in the mouth.
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Corrosion
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Corrosion is the result of these.
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Galvanic currents
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This is the surface reactions of metals in the mouth from components in saliva or foods resulting in corrosion.
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Tarnish
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The _________ of the materials in the mouth and the ___________ of oral fluids by the material are important criteria in their selection.
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Solubility
Sorption |
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What is wettability?
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A solid's affinity for liquid-hydrophobic & hydrophilic.
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What is the average biting force of a person with natural teeth?
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77 kg.
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What are the molars biting forces?
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580 N
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What are the biting forces of the bicuspids?
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310 N
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What are the biting forces of the cuspids?
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220 N
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What are the biting forces of the incisors?
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180 N
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Patients with restorations and prothesises can have their biting forces decreased by...
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...50-80%
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What are the 3 types of stress a dental material can experience?
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1. Tensile (pulling)
2. Compressive (squeezing) 3. Shear (sliding) |
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Deformation/Length=
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strain
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Elastic modulus (stress/strain) is a measure of...
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...the stiffness of a material
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2 reasons for dentures to be made from a rigid material:
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1. Load distribution
2. To be used in thin sections without bending |
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What is a material's proportional limit?
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The stress on the stress/strain curve when it ceases to be linear. Where it begins to bend.
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What is a material's yield limit?
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The stress at which it is permanently bent.
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What is the ultimate strength of a material?
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The stress at which that material fractures.
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Elongation & Compression...what are they?
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The amount of deformation that a material can withstand before rupture. The material's brittleness. (Elongation-tensile; compression-compressive stress)
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Elongation is a measurement of...
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...ductility.
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Compression is a measurement of...
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...malleability.
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Ductility is related to ________ stress.
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tensile
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Malleability is related to ________ stress.
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compressive
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Alloys with less than __ percent elongation are considered to be brittle.
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5%
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What is resilience?
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Energy required to deform a material permanently.
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What is toughness?
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Energy required to fracture a material.
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What is hardness?
What is hardness measured by? |
Hardness is the ability of a material to resist indentation.
Hardness is measured in Knoop hardness. |
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What is an intaglio surface?
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The inner surface of a veneer restoration.
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What are the 2 major categories of all ceramic systems?
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1. Silica based (glass based)
2. Non-silica based (high strength) |
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Feldspathic porcelain...what are the 3 main ingredients?
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1. Feldspar (alkaline alumina silica)
2. Silica 3. Kaolin (Clay) |
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What is the chemical formula for feldspar?
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K20*Al2O3*6SiO2
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What is the chemical formula for silica in the form of pure quartz?
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SiO2
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What is the chemical formula for Kaolin?
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Al2O3*2SiO2*2H2O
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What does kaolin add to feldspathic porcelain?
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Opaqueness. Also more sticky so the tech can more easily shape the material.
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Define glasses.
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Materials that solidify without an organized, crystalline structure.
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What makes glass translucent?
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It is one continuous matrix...there is nothing to scatter the light.
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Glass-flexual strength?
Brittleness? |
Low flexual strength and high brittleness.
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Why is it so easy for a crack in glass to spread?
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There are no boundaries to stop its 'flow'.
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What is the strength of glass?
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60-90 megapascals. Could not be used as a 'stand alone' material. It must be bonded to other, stronger materials.
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Besides traditional feldspathic porcelain, what is the other silica-based material used for ceramics?
Who invented it? |
Reinforced feldspathic porcelain.
Introduced by John McClain (also developed glass ionomer cement) |
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How is reinforced feldspathic porcelain created in the lab?
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Combine feldspathic porcelain powder with Al Oxide (alumina) powder. Fire them to the MP of feldspathic powder (~1000 degrees C--with 2 ingredients fire to the lower MP).
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How is alumina suspended in reinforced feldspathic porcelain?
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Alumina's MP is way higher (~2000 degrees C) than feldspathic's. FS melts and then rehardens with the unmelted particles of alumina stuck in the glass. Alumina particles prevent cracks from perpetuating.
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What is the flexual strenght of traditional feldspathic?
Of reinforced feldspathic? |
Trad: 60-90 megapascals
Reinforced: about 160 megapascals |
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Reinforced feldspathic porcelain is a _______ based restoration.
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Glass. Glass is the matrix, alumina is the filler.
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What is the most popular type of reinforced FS porcelain?
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Leucite reinforced FS porcelain
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How do you create a leucite reinforced FS porcelain?
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Fire FS porcelain against an oxide layer.
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For what are leucite reinforced FS porcelains used?
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*Onlays (up to 1st molar)
*Single units (up to 1st molar) *Veneers *Inlays |
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What is the flexual strength of the leucite reinforced FS porcelain?
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220 megapascals--still require bonding for longevity.
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What are the limitations of leucite reinforced FS porcelain?
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1. 220 megapascals, require bonding for longevity
2. very translucent, if going over discolored teeth it cannot mask the foundation color. |
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How do you bond reinforced FS restorations?
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1. Roughen the surface by applying an acidic agent (usually HF acid)
2. Apply adhesive (usually Bis GMA) to this roughened surface for a mechanical lock |
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Can silica based agents be etched?
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Yes.
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What are the three types of reinforced FS porcelains?
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1. Alumina reiniforced FS
2. Leucite reinforced FS 3. Lithium disilicate reinforced FS |
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What percentage of Lithium disilicate particles are condensed in glass? What does this tell us?
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66%-The strongest silica based material (360 megapascals)
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What is the flexual strength of Lithium disilicate reinforced FS?
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360 megapascals
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What were lithium disilicate reinforced FS designed for primarily?
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Fixed partial bridges and dentures (very strong)
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What are the 2 types of non-silica based ceramic-type materials?
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1. Alumina based (aluminum oxide based)
2. Zirconium based (zirconium oxide based) |
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What are the two types of alumina based non-silica materials?
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1. Glass infiltrated aluminous porcelain
2. Densely sintered alumina |
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What was the major problem in fabricating a coping/framework for alumina?
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Shrinkage
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What is the precentering temperature?
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A temperature high enough to cause the particles to start moving, one towards the other and fuse at the grain boundaries.
Not a lot of fusion, but still good enough to prevent shrinkage-higher temp causes more fusion but mor shinking Allows for glass infiltrated aluminous porcelain |
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Glass infiltrated aluminous porcelain is a ______ based restoration.
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Alumina. Glass is the filler, alumina is the matrix.
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What is the flexual strength of glass infiltrated aluminous porcelain?
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450 megapascals
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Glass infiltrated aluminous porcelain was the first ceramic crown that was able to do what?
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Be cemented on its own. (Still have to apply FS on top of it-this is just the coping) It was the first to be able to survive the forces of mastication.
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What are the indications of the glass infiltrated aluminous porcelain?
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Single units up to the 1st molar.
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What is densely sintered alumina?
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Non-silica.
Alumina particles are fired all the way. Densely sintered-no porosity. |
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What is the flexual strength of densely sintered alumina?
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700 megapascals
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Where can a densely sintered alumnia crown be used?
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Anywhere in the arch.
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What is the biggest obsticles with densely sintered alumina?
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Shrinkage (Al oxide 5-20% shrinkage)
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How can one compensate for the inevitable shrinkage of densely sintered alumina?
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Put alumina on bigger die, raise temp until stable, pull die out yielding a big coping.
Now raise temp all the way up, will keep shinking when reaches original dimension of die. Uses CAD (comp assisted design) CAM and milling |
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The radiopacity of densely sintered alumina?
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Similar to tooth dentin.
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Non-silica based vs. Silica based with regard to translucency?
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Non-silica-Opaque
Silica-Translucent |
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What is the flexual strength of zirconia based non-silica?
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About 1000 megapascals
The strongest coping of all ceramic materials. |
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In an all ceramic bridge, what dental material are you most likely to use?
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Zirconia based non-silica.
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What is major limitation of zirconia based ceramic?
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Shrinkage-need to formula of shrinkage so you can compensate for it. (Enlarge die with gypsum or other methods)
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