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30 Cards in this Set
- Front
- Back
What is a composite?
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A compound of 2 or more different materials with properties that are superior or intermediate to those of the individual constituents.
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What composes composite?
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1. Matrix
2. Filler particle 3. Coupling agent 4. Optical-modifier 5. Initiators & accellerators |
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What are the two viscous liquid organic polymer matrix oligomers?
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1. Bis-GMA (aromatic oligomer)
2. UDMA (urethane diacrylte oligomer) |
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What do the inorganic filler particles of a resin do?
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1. Improve physical and mechanical properties of the matrix
2. Reduce the polymerization shrinkage 3. Reduce water sorption & coefficient of thermal expansion |
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What is the shape of resin's inorganic filler particles?
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Spherical or irregularly shaped
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What are the inorganic filler particles of resins composed of?
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Quartz, lithium aluminum silicate, zirconia, barium, strontium, zinc, or ytterbium glass
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Rank the following inorganic filler particles from largest to smallest:
Microfine Nano Macro Micro |
Macro > Micro > Microfine > Nano
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Micro-filled composite:
What % filler particle? How is its polishability? Which classes is it for? |
32-50% vol filler particle
Very good polishability For class III & VI |
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Micro-Hybrid composite:
What % filler particle? What is it a hybrid of? Strength-Strong or weak? Which classes is it for? |
60-70% vol filler particle
Hybrid of micro & microfine filler particles High strength For all classes |
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Nano-filled composite:
What % filler particle? Polishability? Strength? Which classes is it for? |
78.5% vol filler particle
Very good polishability High strength For all classes |
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What is a coupling agent for resins? What does it do?
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Silanes-A bifunctional molecule
It provides bonding of the inorganic filler particles to the resin matrix |
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What does an optical modifier do? What is it made from?
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An optical modifier is a pigment that use inorganic oxides to match different shades.
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What are the 3 steps of addition polymerization?
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1. Initiation
2. Propagation 3. Termination |
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Composite resins (shink or expand) during polymerization?
What direction is determined by... |
Shrink
...shrinkage direction determined by cavity shape and bonded surfaces (c-factor) |
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How do you calculate c-factor?
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Bonded surfaces/Unbonded surfaces
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Where does resin polymerization cause mechanical stress?
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1. Enamel/dentin
2. At interface 3. In restoration |
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What are some consequenses of resin polymerization shrinkage?
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1. Postop sensitivity
2. Microleakage 3. Secondary caries |
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How can resin polymerization shrinkage be reduced?
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1. More and smaller fillers
2. By using soft-start curing lights 3. Layer composite in 2 mm increments with low c-factor |
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What do bonding agents do?
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Provide resin composites with attachment to tooth structure/ceramic/metal (Adherend)
Adhesive |
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What is an adherend?
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The substrate that an adhesive (bonding agent) is bonded to (enamel/dentin)
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What are 3 different mechanisms that can be used for bonding resin composites?
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1. Micromechanical
2. Chemical 3. Van der Waals bonds |
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What are 3 factors that affect adhesion to tooth structure?
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1. Physico-chemical & mechanical properties of the adherend and the adhesive
2. Surface contamination, wettability (contact angle), & adaptation 3. Oral environment |
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What is the % breakdown (by weight) of enamel?
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95% Inorganic
1% Organic 4% Water |
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What is the % breakdown (by weight) of dentin?
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70% Inorganic
20% Organic 10% Water |
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Etchants:
pH level? What type of acid? |
pH = 1
A thixotrope gel (Phosphoric acid) |
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Primers:
Hydrophilic or hydrophobic? Monomers or oligomers? What solvents? |
Hydrophilic
Monomer Solvent: acetone, alcohol, water, solvent-free |
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Adhesives:
Hydrophilic or hydrophobic? Monomers or oligomers? |
Hydrophobic
Dimethacrylate oligomers Compatible to monomers in primers and composites |
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What about enamel allows resin better wetting of the surface and penetration into the micro porosities?
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Its high surface energy.
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How long should enamel be acid etched for?
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15-30 seconds...longer for uncut or primary enamel.
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How long should dentin be acid etched for?
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15 seconds with 37% phosphoric acid.
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