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100 Cards in this Set
- Front
- Back
a dimensionally stable material that is plastic during manufacture and contains large molecules is called
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plastic
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a chemical compound consisting of large organic molecules formed by the joining of many small repeating monomers is
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polymer
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the temp at which thermal coefficient of expansion increases abruptly and the material gets increased mobility
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Tg - glass transition temp
characteristic of glassy structures |
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What kinds of materials are used at temps abover their Tg
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Maxillofacial prosthetics and impression materials
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What kinds of materials are used at temps below their Tg
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restorative resins
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a resin that softens on reheating above Tg and is fusible, soluble in organic solvents has better flexural and impact properties and generally not cross linked is called
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Thermoplastic
generally have 2ndary bonds between chains(impression compounds, acrylic resins, denture teeth) |
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What are the 4 steps of free radical polymerization
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activation and initiation, propagation, termination, chain transfer
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What is step growth or condensation polymerization
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simple chemical reactions that form byproducts, eliminate small molecules or repeated functional groups
slow(seen in polysulfides and condensation silicone -both impression materials) |
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the amount of monomer available for reactino whcih actually took part is called
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Degree of monomer conversion
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the avg number of monomer units which have been incorporated into a polymer chain
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Degree of polymerization
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total number of monomer units divided by total number of molecules is what
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Number Average degree of Poly. IE Xn
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weight of the sample divided by the number of moles it contains is called
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Weight Average degree of Polymerization. IE Xw
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t or f typicall Mw is >= to Mn
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true
Mo = molecular weight of structural unit Mn = number average mol wt = Mo * Xn Mw = weight average mol wt = Mw * Xw Polydisperity = Mw/Mn |
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what is the formula for polydispersity
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Mw / Mn
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What type of polymerization reaction forms no by products, needs double bonds and radicals to proceed, has no change in composition and is a fast reaction
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Free Radical or Addition Polymerization
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why is UV light not used to activate polymerization
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it can hurt the retinal and unpigmented eye tissues. It also gives poor depth of cure
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What is the wavelength that we must use to activate our polymerization reactions
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470-500 nm
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What is methyl ether of hydroquinone used for
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inhibition of polymerization by preventing spontaneous poly, affecting working and storage times and degree of polymerization
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What inhibitor causes a sticky layer of underpolymerized resin on the restoration surface
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Oxygen
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What do plasticizers do
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Added to reduce the softening temp by neutralizing secondary bonds or intermolecular forces.
they also reduce strength, hardness |
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T or F plasticizers can be both internal(by copolymerization) or external(not commonly used)
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T
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What are the three types of copolymers
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Random
Block Graft or Branched |
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What are the rheometric properties of polymers caused by
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plastic flow when polymer chains slide over one another and relocate
elastic recovery in amophorous regions when coiled chains straighten under force and recoil after force is gone |
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What kind of deformation and recovery due polymers undergo
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Elastic def,plastic def and viscoelastic def(slow recover after stress is eliminated)
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T or F plastics have high degree of permanent deformation and small amount of elastic recover(viscoelastic behavior)
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T
note its elastomers that have a small amount of plastic deformation |
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What does the solvation properties of polymers depend on
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polydispersity, cross linking, crystallinity and chain branching
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T or F polymers tend to absorb water, swell and become soft in solvents
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T
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Do highly crosslinked polymers dissolute in water easily
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no
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If inter carbon distances increase during polymerization then why is shrinkage a problem
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inter carbon distances definitely increase during polymerization but the overall effect is shrinkage due to going from a liquid(4.0 ang) to a solid(1.9 ang)
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For small amounts of shrinkage, volumetric shrinkage is approx how many times linear shrinkage
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3
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What are the four types of dental resins
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Acrylic
Methyl methacrylate poly(methyl methacrylate) Multifunctional resins- bis-GMA, TEGDMA, HEMA, UEDMA, PAA, PENTA-P |
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what type of resin is an ethylene derivative with a vinyl group and are hard, transparent and imbibe water
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Acrylic REsins
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What are the physical properties of methacrylate resins
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strong, resilient, resist wear and occlusal forces, dimensionally stable and have low specific gravity if used for dentures(helps suction activity with saliva)
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A liquid monomer that is clear, transparent has a high vapor pressure and is an excellent solvent that can be activated by light heat or chemicals is called
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Methyl Methacrylate
also can polymerize at room temp in air and has 21% volumetric shrinkage upon polymerization |
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what monomer is hard, transparent, transmits uv light, is stable and doesn not color with age
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poly(methyl methacrylate)
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what monomer is an aromatic ester of dimethylacetylate that is synthesized from expoy resin(ethylene glycol of bis phenol A) and methyl methacrylate
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Bis GMA
also very viscous so TEGDMA is used to thin it out |
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a compound of two or more distinctly different materials such that the compounds properties are superior to that of the constituents is called a
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composite
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what are the compositions of enamel, dentin and
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enamel 1%wt enamelin and 90-92 hydroxapetite and water
dentin 18 wt% collagen and 75 wt% hydroxyapetite and water |
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in the 40s and 50s what esthetic, insoluble, insenstive to dehydration and inexpensive material that was easy to manipulate was used
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unfilled acrylic resin
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why were filler particles added to acrylic resin
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reduce the high polymerization shrinkaage and high thermal expansion coefficient
note the lack of filler to resin chemical bonding resulted in high wear, filler loss and roughening/staining of surface |
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What are the components of a composite resin
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REsin matrix(continous phase- he stressed this)
filler particles(dispersed phase- stressed this to) coupling agent activator-initiator inhibitor modifiers, opacifiers and UV absorbers |
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Who developed bis GMA(bisphenol A-glycidyl methacrylate)
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Dr. R. L. Bowen
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describe bis GMA
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high weight, highly viscous, very cross linked multifunctional resin that has better properties than acrylic resins like methyl methacrylate
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BisGMA has ____ times molecular weight and ____ density of methyl methacrylate double bonds
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5, 1/5
this leads to a proportionately less polym shrinkage than |
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name some dimethylacrylate monomers that are resin matrix materials
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bis GMA(widely used)
UDMA - monomer with one or more urethane groups and two methacrylate end groups TEGDMA - low mol weight, diluent monomer that permits addition of a high filler content and creates a composite resin with a usable consistency HOWEVER IT INCREASES POLY SHRINKAGE AND WEAR OF THE RESIN |
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what was the first filler particle used that was hard and abbrasive
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Quartz, glass amorphic silica fillers
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how are microfillers made
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precipitation of pyrolytic processes, they add viscosity and improve consistency
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What are some radiopaque fillers and why are they used
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Ba, Sr, Zr glasses, used so you can see where fillings are on radiographs
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what is the primary purpose of fillers
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strengthen composite resin and reduece amount of matrix material
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what properties are improved due to increased filler loading
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Reinforcement of matrix resin which gives higher hardness, strength and decreased wear
reduction in poly shrinkage reduction in thermal exp coeff improved workability due to incr viscosity reduction in water sorption, softening and staining increased radiopacity and diagnostic sensitivity(Ba, Zr, Sr) |
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what does the matrix-filler thermal coeff mismatch help do
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toughens material
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name some things the filler-matrix comb does
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lowers pol shrinkage,
lowers CTE-(produces less interface stress) improves compressive and tensile strengths reduces water sorption and softening |
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what are organosilanes(gamma-MPS and vinyl tricholrsilane) used as
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Coupling agents -they bridge the Silanol groups on the filler surface to the siloxane bonds of the coupling agent as well as binding covalently to the methacrylate groups of the resin
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what permits transfer of stresses from matrix to stiffer filler particles
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coupling agents(organosilanes)
they improve mechanical and physical properties and provide hydrolytic stability |
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what are the 4(loosely used cause he said 3 in class but were four in handout) types of activator initiator systems
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chemically acitvated - 2 pastes benzoyl peroxide initiator and tertiary amine activator
light activated - single paste containing camphoroquinone (photosensitizer molecule of wavelength about 470 nm <= .2 wt%)and aliphatic amine initiator(.15 wt% DMAEMA) dual cured systems(usually in resin cements nor restorative materials) - two pastes, benzoyl peroxide and camphoroquinone in one and tertiary amine activator in the other paste - then light cured for -usually for places where light may not completely penetrate heat activated - direct and indirect composites can be subjected to additional curing by heat in an oven |
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what is the inibitor added into the composite resins today
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.01 wt% butylated hydroxytoluene)
minimize spontanteous polym. ensure good work time and extend shelf life |
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T or F ligher and less opaque shades are more difficult to polymerize
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F, darer more opaque shades are tougher to polymerize
NOTE place in thinner layers to get complete polymerization |
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what are two problems caused by air bubbles that are formed when mixing chemically activated resins
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trapped air bubble voids
Oxygen in voids inhibits polymerization |
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Whats some more disadvantages of chemically activated resins
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no control on work time - once mixed you only have so long
disturbing polymerization during setting causes problems, so you cant disturb it for a few minutes after inserting it |
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What do voids in chemically activated resins cause
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Voids relieve stress by relaxtion and slower curing results in internal flow to compensate for polym shrinkage
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What is an advantage of light activated resin systems
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you can work it and contour then light cure it(COMMAND POLYMERIZATION)
note- not as sensitive to oxygen inhibition |
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What wavelength range is used in most light cure systems
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400-500 nm
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Describe the QTH light system
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Quartz tungsten halogen - they need a filter to produce inthe 400-500 range has 350 mW/cm^2 radiant poer density
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what is another word for light intensity
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radiant power density
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describe the blue light emmiting diode light system
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blue light emitting diode - emit light in very narrow range 440-480 nm, can be battery powered, have long moderate curing times, compact mobile, generate less heat so they dont have cooling fans, light filters not needed
NOTE MAY NOT WORK WITH NON CAMPHOROQUINON CONTAINING ADHESIVE RESIN |
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describe plasma arc curing lights
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have gas like xenon ionized to produce plasma(thus high intensity 1800-2000 mW/cm^2), must be filtered to get 400-500 nm range, have short curing times but create tremendous heat which might be hazardous to soft tissue and pulp, have smaller diameter tips and are 2-3 times more expensive
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describe argon laser lights
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very high radiant power density, very narrow spectrum(around 490 nm so may not cure all types of resins), 3-4 times more expensive, small diamter tips, short cure times, high maintenance costs and is very bulky, requires dedicated power source
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what is DC
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degree of conversion - percentage of C=C bonds consumed based on the formula below
DC= (1-R) * 100 R = ratio of unreacted methacrylate groups before and after polymerization |
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What oes a higher DC value mean
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better strength and wear resistance
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What does DC depend on
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composition, transmission of light, and amounts of activator, initiator and inhibitor
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What is the typical DC value
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50-70 %
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what is the thickness of a resin that can be converted from a monomer to a polymer under a specific light curing condtion
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depth of cure
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what things can changed light intensity of QTH unit
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age and quality of light source, orientation and distance of light from tooth and contamination of tip
NOTE CHECK LIGHT INTESITY WITH RADIOMETER FREQUENTLY |
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what are the classifications of composite resins(4)
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Traditional - (macrofilled) 8-12 micrometers
Small particle Filled - (SPF) 1-5 micrometers Hybrid - .5- 1.0 micrometers = filers from 2 different size ranges Microfilled - .04 - .40 micrometers - can be home or heterogeneous |
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Whats in a traditional(conventional or macrofilled composite)
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70-80 wt% or 60-70 vol% ground amorphous silica and quarts filler which are radiolucent
phys and mech properties much better than unfilled acrylic resins |
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How does a traditional composite compare to unfilled acrylic resin
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higher compressive and tensile strength, hardness, elastic modulus and wear resistance
lower CTE and less polym shrinkage |
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what is a drawback of traditional composites
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rough surface due to wear by selective abrasion of softer resin matrix which allows discolorization
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Describe small particle filled composites(usually in posterior teeth)
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more inorganic filler (80-90 wt% or 65-77 vol%) than traditional composites.
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Why is amorphous silica filler added to small particle filled composites
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radiopacity
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Which composite of the 4 types has the best physical and mechanical properties
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small particle filled- thats why they are used in posterior teeth most oftenly
also has best wear resistance and surface smoothness heavy metal fillers hydrolize soften and wear |
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which composites of the 4 types is used most oftenly for ant teeth
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microfilled - has very smooth surface finish but have weak bonds between composite particles and matrix which cause wear by chipping, staining and cracking --DONT USE IN WEIGHT BEARING RESTORATIONS
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t or f microfilled particles have superior properties than traditional composites
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F, traditional have better properties than microfilled but small particle have best of all 4
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describe the hybrid composite
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filler content 75-80 wt% of colloidal sillica filler and heavy metal containing glass fillers. esthetic with very smooth surface
Properties range between traditional and small particle filled but are superior to microfilled and can be somewhat stress bearing |
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what is a flowable composite
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modified hybrid and SPF composite
USUALLY USED AS PREVENTIVE RESIN RESTORATION |
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flowable composites have properties similar to what
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compomers - have high flexibility, low elastic modulus but are more susceptible to wear and have higher polymerization shrinkage
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T or F direct posterior composites are better for conservative restorations
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T, amalgams should be used for more invasive restorations
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what are some drawbacks of direct posterior composites
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poor interproximal contacts
gingival margins can have interfacial gap due to pol shrinkage when restorations are in dentin or cementum not as polishable high rates of occlusal wear in contact and non contact areas(10-20 micrometers/year) |
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what are packable composite resins commonly mistermed as
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condensable resin
they are highly filled composite resins(>80 wt%) |
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T or F packable composite resins can be bonded to the mandible
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F all composites must be bonded to the tooth with some form of bonding resins
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what are the advantages of packable composite resins
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low shrinkage 2-3% vol
low wear rates - comparable to indirect composite and amalgam high depth of cure(>5 mm) no sticking or slumping of resin high elastic modulus(stiffness) |
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what are the disadvantages of packable composites
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poor interproximal contacts
poor adaptation to tooth due to high viscosity not many shades mot very polishable high spots not burnished away as in amalgams DONT OVERFILL MATERIAL IN PREP some products crumble easily |
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what are the 2 types of posteriior composite resins
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indirect - fabricated in lab then cemented to tooth, have less wear and shrinkage you can do direct inlay made in patients mouth and further polymerize in lab or do indirect inlay where you take impression and inlay fabricated in lab on a die
direct |
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what were veneer resins originally made of
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poly (methyl methacrylate)
now made of bisGMA |
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How are veneers installed
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polymerized by light or heat+pressure
retained by bonding agents such as 4-META micromechanical retention or silicoating |
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what are some advantages of veneers
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ease of fabrication, intraoral repairability and less oppossing wear
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what are some disadvantages of veneers
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low proportional limit, distorting on occlussal loading, leaking, staining, and less stress resistant
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what can lead to marginal leakage in composites
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poly shrinkage, CTE mismatch with tooth structure(percolation)
water sorption low wear resistance |
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What are some limitations of composites
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Mechanical properties not as good as amalgam
technique sensitive mechanical and chemical degradation in oral fluids does not directly bond to tooth |
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if unpolymerized resin is to close to pulp what can happen
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it can leach components and cause chronic inflammation - very few people show true allergic response to resins
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What causes marginal leakage on composites
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polym shrinkage, can lead to secondary decay and pupal reactions
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