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robbypowell's version from 2016-12-10 20:19

composite

Question Answer
Define: a material consisting of two chemically different components separated by a distinct interface. Thus, when viewed by eye or under the microscope, there will be a definitive demarcation between the material components.Composite material (e.g. fiberglass, concrete, Dentin)
T/F: Properties of composite are better than those of each component aloneTrue
T/F: Properties of composite are less desirable than those of each components aloneFalse (better)
List the three broad categories of monomer systems used in commercial dental composite materials.a. Bis-GMA b. TEGDMA & c. UDMA (urethane dimethacrylate)
_______ used as a common co-monomer in many dental resin systems. It aids in making the co-resin mixture less viscous and easier to handleTEGDMA
Compared to MMA, the dental monomers (Bis-GMA, TEGDMA & UDMA) have _______ (higher/lower) values of polymerization shrinkageLOWER (lower shrinkage is desirable for dental restorations)
What quality of Bis-GMA accounts for it having a lower polymerization shrinkage than MMA?Increased Monomer size, (less space in polymer accounted for by bond, and more by monomer chain means less shrinkage)
Which results in less polymerization shrinkage... larger or smaller monomersLarger --> less shrinkage (ideal in dental materials)
List 3 clinical consequences of polymerization shrinkage - open margins (from pulling away) (white-line, gap formation) - microleakage - tooth strain (during curing resulting in post-insertion pain and sometimes overt cracking of tooth structure)
compared to other materials (ceramics and metals), polymers are _______ (stronger/weaker)weaker (low wear resistance of the restoration, low fracture resistance)
Water sorption combines concepts related to _______ ((to suck up, take in) & ________ (sticking to the outer layer); resulting in color instability, lowered strength & high creepAbsorption (to suck up; to take in) & Adsorption (sticking to the outer layer)
Compared to PMMA, Composites absorb less because the cured matrix is more __________ (stronger and more resistant to deformation forces of water) and it is filled with a material that is not affected by water (the glasslike filler components)Cross-linked
Why is composite less susceptible to water sorption than PMMA?Greater Crosslinking & Filler Material unaffected by water (glass-like filler)
_____ results in a physical change in the material dimensions due to load applied over a long timeCreep
Does greater water sorption increase or decrease creep (change in the material dimensions due to load applied over a long time)Increase
polymers have ______ (high/low) coefficients of thermal expansionhigh
When a tooth and a polymer are both subjected to higher temperature... which expands more?polymer (b/c higher coefficient of thermal expansion)
Clinical implications of higher COTE for polymers than tooth structure is largely Marginal ______; this will mean staining, redecay potential, & sensitivityPercolation
Compared to PMMA Composites have _____ (higher/lower) CoTE, ______ (higher/lower) curing shrinkage, ________ (higher/lower) strength, & _______ (higher/lower) water sorptionLower CoTE; Lower shrinkage, Higher Strength & Lower Water sorption
How does composite compare to PMMA in terms of Coefficient of Thermal Expansion?Composited have Lower Coefficient of Thermal Expansion
How does composite compare to PMMA in terms of strength and what accounts for the difference?Composites are stronger (because of the addition of glasslike particles that are chemically bonded to the polymer network)
How does composite compare to PMMA in terms of water sorption and what accounts for the difference?Composites absorb less (because the cured matrix is more cross-linked, also glass-like filler particles in composite are unaffected by water)
How does composite compare to PMMA in terms of shrinkage and what accounts for the difference?Bis-Gma and composites shrink much less (because of their monomer length) (size)
The _______ phase of composites provides a matrix that holds filler particles and conforms to the shape of the cavity preparation, it can also be termed the continuous phase because it present throughoutOrganic Phase (usually monomer)
The _______ phase of composites is usually referred to as fillersInorganic
How does the addition of filler affect compressive strengthIncrease (desirable effect)
How does the addition of filler affect hardnessincrease (desirable effect)
How does the addition of filler affect water sorptiondecrease (desirable effect)
How does the addition of filler affect thermal expansiondecrease (desirable effect)
How does the addition of filler affect flexural strengthIncrease (desirable effect)
How does the addition of filler affect polymerization shrinkagedecrease (desirable effect) Although! Even with fillers, composites still shrink between 1.5 - 3% by volume, an amount which may have serious clinical implications
Even with fillers, composites still shrink between ___ to ___% by volume, an amount which may have serious clinical implications1.5-3%
Even with fillers, composites still shrink to an extent that can have serious clinical implicationsTrue
With the addition of fillers, composites shrink to an extent that no longer has clinical implicationsFalse (even with fillers, shrink 1.5-3% and this can have serious clinical implications)
List the 3 materials used as fillers in resin composites and state which of these materials provide radiopacity1. Silica Dioxide (SiO2), (basically sand)(NOT radiopaque), 2. Glasses (e.g. barium alumino borosilicate glasses)(CAN be made to be radiopaque) & 3. Zirconia/SiO2 blends (***naturally radiopaque***)
List 3 elements added to glass fillers to make them radiopaquealuminum, barium & strontium
T/F: Silica Dioxide fillers are radiopaqueFalse (restorative materials containing only silica as the filler will not appear opaque on dental X-rays)
T/F: Silica Dioxide fillers are radiolucentTrue (restorative materials containing only silica as the filler will not appear opaque on dental X-rays)
Silica can be formed through evaporation and deposition of materials resulting in extremely small filler particles. This form of silica is termed “_______ silica” and particle size is near 0.04 micronsFUMED silica
What is the size of silica filler particles made through grinding? What about fumed silica?grinding --> ~1 micron (just less than); fumed silica --> 0.04 microns (40nm)(1/10th the size of blue light's wavelength)
What are 2 advantages of Glasses such as barium alumino borosilicate glasses over Silica dioxide fillers? Disadvantages of these glass fillers?Advantages: Cost less to produce, Can be made radiopaque (silica is not); Disadvantage: may slowly dissolve in aqueous media
What is the main advantage of Zirconia/SiO2 blend fillers?Naturally radiopaque
______ agent functions to chemically attach the polymer matrix (via a (C=C) bond) to the inorganic filler particle by means of a silane bond.Coupling agent
Coupling agent chemically attaches polymer matrix to inorganic filler via _____ bondSilane bond
The coupling agent used in dental composites chemically binds polymer matrix to inorganic filler and technically termed an ______-______ coupling agentOrgano-silane coupling agent
In coupling reaction ______ group is released upon attack by water to form ethanol, and an “Si-O” bond is formed between the filler particle and the silane end of the coupling agent, thus covalently bonding the filler particle to the silane coupling agent.Methyl group
T/F: If silane is not present, the organic phase reacts independently of the inorganic phase (decoupling). Thus, silane gives the composite its true propertiesTrue
The effects of coupling agent (organo-silane) affect elastic modulus how?Increase (desirable effect)
The effects of coupling agent (organo-silane) affect strength how?Increase (desirable effect)
The effects of coupling agent (organo-silane) affect thermal expansion how?Decrease (desirable effect)
The silane bond to the filler is sensitive to _________.HYDROLYSIS (If this bond is broken, the filler particle is free to fall out of the polymer matrix, and it will not reinforce the polymer as before. Instead of having one restorative material with the combined properties of two distinctly different components, each material then acts independently of one another. The overall effect is a great lowering of desired physical properties)
to increase filler amount, some material is polymerized and then ground and incorporated back into an uncured polymer matrix. These are termed "_____ fillers""pre-polymerized fillers"
Why are fillers sometimes "pre-polymerized"?to increase filler amount (some material is polymerized and then ground and incorporated back into an uncured polymer matrix)
What are 3 indications for Microfills; Contraindications?Class 3, Class 5, veneer over other types composites (where smooth, polishable surfaces are needed, but not subjected to high stress); Areas placed under high stress (anything that occludes or has retentive clasps or rest seats interacting with it... there are probably more examples)
What is the Product example given of a MicrofillSilux Plus (3M)
Not all "micro-fills" will fall under the description given above. Some are made utilizing a much different method that results in formation of __________ of micro-fillers. These products permit enhanced volumetric loading and have superior physical and clinical properties compared to the conventional microfills described above.“agglomerates”
_____-Hybrids: Addition of nano-sized particles with the larger filler particles that are in general less than 1 micron in size. Thus a mixture of nano-fills and hybrids. They still have a portion of microfill particles in themNano-hybrids
_____-Hybrids: average particle size less than one micron. Provides strength needed with a highly polishable surface (universal composite)(Herculite XRV, Prodigy, Caulk TPH). Usually, the average particle size is near 0.6μm. However, newer products are now being introduced which claim an average particle size of 0.4 μm with enhanced levels of filler loading and polishability like conventional microfillsSub-micron Hybrids
_____-Hybrids: average particle size between one and five microns. Provides more strength, but the esthetics of the final product are less than those of the sub-micron hybrids and micofills. Because of the higher glass loading, these products will be more difficult to polish, and should a filler particle be lost at the restoration surface, the defect remaining will become visibly noticeable.Small Particle Hybrids
_____-Hybrids: Very wide distribution of particle size for the purpose of maximizing filler loading. These products are designed for posterior use and in high stress areas. These materials lack translucency and life-like features, and are thus used mostly for posterior applications.Heavily Filled Hybrids
memorize

classification of composites

Question Answer
We should think of dental composites as a combination of a _________(a)_________ and a _________(b)_________. Those materials with a large proportion of _________(a)_________ will tend to be weaker and softer than those having a large proportion of the _________(b)_________.(a)Plastic; (b)Glass
We should think of dental composites as a combination of a _________(a)_________ and a _________(b)_________. It is much easier to polish the _________(a)_________ components than it is to polish _________(b)_________, so composites with high proportion of _________(a)___ will polish easier, and have a more pleasing esthetic appearance, than those which are heavily filled with _________(b)___(a)Plastic; (b)Glass
This method of describing filler extent can be misleading... and usually this metric is uselessweight percent filler content
This method of filler content presentation is a better indicator of potential performance of the restorative materialVolumetric percent filler content
Generally, volumetric measurements are ___ to _____% lower in value than weight % value10-20% lower
the importance of determining filler content by volume percent as opposed to weight percent is that volume percent will provide you with a true indication of the _____ _____ that is glass and that which is plastic; this is essential when determining its ______ potentialSurface area; Esthetic potential
T/F: Nanofills are made from grinding silicasFalse (Not made from grinding silica, special method used to “grow” fillers to specific sizes)
T/F: Nanofills are not made from grinding silica, special method used to “grow” fillers to specific sizesTrue (“true” nanofilled particle is 10 nanometers or less)
“true” nanofilled particle is ___ _____ (#, unit) or less10 nanometers (0.01microns)
T/F: because of the small size it is difficult to keep nano fill particles from clumping togetherTrue (10 nm or less)
T/F: practitioners must be careful because manufacturers often change their units describing filler particle size and then call them nanofillTrue
What are Nanofill composites especially known for?ability to maintain a highly polished, lustrous surface over time
Fumed silica creates what size of particles... (nano-fill, micro-fill or small particle)Micro-fill (size averages near 0.04 μm or 40 nm)
memorize

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