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126 Cards in this Set
- Front
- Back
What are the 4 different mechanisms of adhesion?
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Mechanical, adsorption, diffusion and electrostatic
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What type of adhesion has interlocking of the adhesive with irregularities in the surface of the substrate, or adherend
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mechanical
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What type of adhesion has chemical bonding between the adhesive and the adherend.
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adsorption
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What type of adhesion has interlocking between mobile molecules
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diffusion
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What type of adhesion has electrical double layer at the interface of a metal with a polymer that is part of the total bonding mechanism.
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Electrostatic
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What type of adhesion uses ionic, vanderwaals, covalent or hydrogen bodning?
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adsorption
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what adhesion has precipitation of substances onto tooth surfaces that resins can bond to? (uses this mechanism
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diffusion
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what adhesion uses this mechanism? penetration of resin into tooth that forms tags
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mechanical
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what adhesion uses this mechanism?
chemical bonding to the inorganic component (HA -hydroxyapatite) or organic components - (mainly type I collagen) of tooth structure |
adsorption
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T/F a combination of the previous mechanism is possible
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true
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T/F ALMOST every case of dental adhesion is based primarily on mechanical bonding.
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true, chemical bonding may occur as well, but generally makes a limited contribution
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What are the requirements for adhesion?
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good wetting, clean surfaces
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many parts are ________ one part are _____-
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polymer,monomer
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monomers are in what phase?
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liquid
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What are the reactions of radical polymerization?
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initiation, activation, propagation, termination
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These kind of reaction usually occur with unsaturated molecules containing double bonds (usually difunctional, MMA (methly methacrylate) is monofunctional)
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free-radical polymerization
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are there any by-products after polymerizatin?
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no
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________ monomers, widely used in dentistry, undergo chain reaction polymerization.
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acrylic
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What is an accelerator to increases the rate of activation?
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chemical, light, heat
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_______ or _________ can consume newly formed free radical and prevent or postpone initiation.
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inhibitors or retarders
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in the termination phase, is there more than one possibe event?
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yes,
propagation continues, until all monomers were used up if it were not for the strong endency of radical to react in pairs this tendency is overcome by the use of small amount of initiators (radical species) and large amounts of monomer. |
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When you create a structure with 2 double bond = rigid cross-linked structure, give an example of this with what we use.
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dimethylacrylate
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When the structure has 1 dble bond and creates linear chains (_______) then it is a monomethylacrylate.
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plastic
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Name so advantages of pure polymers:
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Can control viscosity
Easily wet surfaces Adhesives are solvent diluted monomer |
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During activation the ______ bonds are broken and can then be added to.
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double
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During the propagation phase does the volume ________ (inc.dec.)
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decreases, making linear polymers. with monomethylacrylate
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POlymers use ______- bonds. They have a ________ molecular weight. and long molecules are usually composed of non- ______ elements. (usually CONH - organic)
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covalent, high, metallic
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What is a disadvantage to using polymers?
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shrinkage, (the more volume, the greater shrinkage) - pure resins sed primarily in thin films.
poor wear resistance: inorganic fillers added to improve wear and reduce shrinkage (composites) |
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What can you add to decrease the disadvantages of polymers
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add inorganic fillers = composites
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To make the composite you mix (thick) _______ with (watery) ______ to fll all grooves (becuase you can't fill spaces with honey!)
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monomer, polymer
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What are the two phases of dental composites
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matrix phase
dispersed phase |
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________-- ________ is the (continuous phase). has monomer resin, photoinitiars, and pigments
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matrix phase
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_____ ______ is the discontinuous phase. has glass fillers and silane coating
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dispersed phase
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_______-- resin is when you have a mixutre of two or more materials.
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composite
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T/F The goal of composite resin is to blend properties of the parts to obtain intermediate properties and take advantage of the best properties of each phase.
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t
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A dental composite is a ______- (filler phase) mixed into a _______-- (matrix phase).
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dispered matrix
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What are the methods of polymerizing composites?
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self curing, ultraviolet light curing, visible light-curing, dual curing, staged curing, can't fill to level of enamel with our materials
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When something is harder/strong has more ______- content.
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mineral
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T/F silicate glasses, strengthen and have optical properties
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true
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What makes the initial mixture of dental composite fluid and moldable
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acrylic monomers
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The composite resin is supplied as a past (whether it is thick or thin depends on ________)
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filler content
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Usually ___- the matrix of any system produces more desirable clinical properties.
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decreasing
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what is the phase that generally is transiently fluid during manipulation or placement of teh material; tend to have the least desirable properties; usually decreasing teh matrix of any system produced more desirable clinical properties
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continuous phase
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It is important for the _____ phase to be bonded effectively to the _______ phase to distribut ________ within the system to all phases.
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disperesed, continuous, energy
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How do you classify the composite resin?
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by the size of the filler
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Why type has a (mix) with colloidal microfils and paste like stuff?
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Hybrid type - has colloidal microfill and silicates
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What is the purpose of having colloidal microfills?
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helps to keep fills suspended
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What filler size corresponds to these?
10-100 microm 1-10 microm .1-1mcicrom .01 - .1 microm |
macrofill
midifill minifill microfill nanofillers are the smallest - these are all nanofillers |
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fillers bond to ______ phase
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resin
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what elements are found in silicate glasses:
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barium zinc and yttrium -modified silicate glasses currently most popular fillers
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what is the most popular filler used today?
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modified silicate glasses
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in modern composites silica particles are _________ with monomolecular filsm of _________ coupling agetns
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precoated, silan
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there are many various sizes, but the bigger the filler the ______ the surface
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rougher
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______ _______ ______ are difunctional molecules that couples or bonds fillers to polymer; provies interfacial bonding between the phase
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silane coupling agents
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when do silane coupling agents work best?
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with silica particles, thus all composites have been based on silica -containing fillers
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What elements are added to produce radiopaque qualties of the filling? in non-crystalline filler
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Ba, Zn, B, Zr, Y ions used to produce radiopacity in filler particles - makes radiodiagnose easer on x-ray.
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non-crystalline (glasses) has been modified. What element are added to make the filling softer?
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Na, K, and CA
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non-crystalline (glasses ) have been modified. What elements are added to make the filler more crushable?
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Al, Li
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Crystalline is radioluscent, why?
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quartz, crystobalit, trydymite - radioluscent, very hard and abrasive - don't have elements that no -crystaline have.
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Is the filler surface hydrophobic or philic?
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philic
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What is the bifunctional molecule that bonds to the filler surface and changes it from a philic to a phobic and assist in bonding the filler to the polymer.
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silane
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Composite monomers are hydro____
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phobic
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Bis-GMA has high viscosity
UDMA - moderate viscosity TEGDMA - low viscosity These are all examples of what? |
composite MONOMER
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What material do we use when we make custom tray?
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dimethylacrylate
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Bis-GMA and UDMA have a ______ mol. weight
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higher
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TEGDMA ________ like h20
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runs
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the Bis-GMA and UDMA recude shrinkage, but what is the disadvantage?
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difficult to mix filler in with
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the glass surface is hydro_ and the monomers are hydro ____--
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philic,phobic - thus they have poor wetting and no bonding - so USE SILANE!
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something unique of composite monomers is that they have ____- functional gropus on each side and can make cross-linked structure = more riged
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2
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T/F bis-GMA is an oligomer
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true
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What are examples of resin matrix?
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bisGMA, UDMA, TEGDMA
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Oligomers are known to be ____.
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thick
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t/F udma is an oligomer?
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true
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t/f TEGDMA is an oligomer?
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false, it is a DILUTENT
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how does TEGDMA improve degree of polymerization
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more dble bonds convert, better physical and mechanical properties.
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What do most composites empoy as a photoinitiator?
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camphorquinone - yellow in color absorbs blue light
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What are the three levels of dentinal reaction to caries?
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reaction to long term, low-level acid demineralization associated with slowly advancing lesion
reaction to a moderate -intensity attack reaction to sever, rapidly advancing caries characterized by vary high acid levels |
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What determines the material structure?
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atomic arragnetment: crystallin vs. non crystallin
bonding: primary (metallic, ion, covalent), secondary (hydrogen, van der waals) composition: elements and phases) Defects: macroscopic (pores) atomic scale (microflaws) |
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What are the materials properties?
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physical: environment
chemical: bonding affeted biologic: living tissue Mechanical: forces |
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In 1955 what was an introduction of acid-etch technique?
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buonocore
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what percentage of phosphoric acid did buonocore use?
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85
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What is the first step in enamel bonding?
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etching dissolves some mineral (like caries)
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what leave a very irregular enamel surface (whitish looking like incipient caries)
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etching
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When a low viscosity monomer (fluid resin-based material - TEGDMA) where does it go?
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the resin flows into microporosities (added by capillary action)
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monomers in the material polymerize and become ________ with enamel
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interlocked
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formation of ______- within the enamel surface is the fundamental mechanismof adhesion of resin to enamel
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microtags
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what are the two types of resin tags
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macrotags, and microtags
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_ is a resin tage which forms between enamel and rod peripheries
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macrotags
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_ is a smaller tag that forms from resin penetrating dissolved crystals
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microtages
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t/f the chemical composition of enamel varies
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t, if the surface has been removed, fluorinated, demineralized and remineralized are all of different composistion
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what kind of acid is used for etching?
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phosphoric
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what is the concentration of the acid we currently use?
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most current phosphoric acid gels are 30-40% -
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concentration too low or too high can result in
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formation of precipitates, or poorly defined etch patterns respectively
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What are the main etching variables
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time (some studies suggest as low as 15 sec.)
etchant form (liquid, gel) rinse time (20 sec) chemical composition of enamel |
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what is used for the interprism resin penetration?
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macrotags
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etching can increase ______about 2000x
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surface area
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ENAMEL ETCHING CAN RESULT IN __ different micromorphologic patterns
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3
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Type I etching is mainly through ______ bonding
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mechanical
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Properties of a material depend on the direction; for example, wood. In a piece of wood, you can see lines going in one direction; this direction is referred to as "with the grain". The wood is stronger with the grain than "against the grain". Strength is a property of the wood and this property depends on the direction; thus it is ________
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anisotropic:
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The stronger bonding occurs where in enamel bonding?
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rod ends
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Th weaker bonding occurs where in enamel bonding?
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to sides of rods because enamel is anisotropic - not bonding to the 'grain' of the wood
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t/f enamel structure is very consistent regardless off location.
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true
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t/f enamel can be dry with no moisture
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true
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t/f dentin can be dry with no moisture
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fAlse
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how long can sealants last?
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10-20 years
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are enamel bonds long lasting and durable?
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true
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what is easier to place, and enamel bond or dentin bond
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ENAMEL
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do sealants wear away?
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they tend to slowly wear away until only small amount left in the grooves
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When dentin bonding do you still etch?
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yes, the dentin surface was altered from cavity prep,
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What does etching surface of dentin serve to do?
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enlarges tubular openings
remove or solubilize smear layer (ideally would leave smear plugs which would greatly reduce dentin permeability and sensitivity) demineralize surface detin |
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What do you have to be careful of etching dentin in relation to the demineralization of surface dentin
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removes much of the surface HA; leaves interconnected network of collagen fibrils. too much etch - too much demineralization - weak layer between restoration and tooth
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what are the problems of dentin bonding?
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LOTS OF WATER - the enamel adhesives are very hydrophobic - so wouldn't completely penetrate SMEAR LAYER covered surface and was loosely attached (weak link like painting a greasy wall-paint peels off)
DENTINE STRUCTURE DIFFERS with location and age |
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t/f the dentine structure differs with location and age
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treu
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how should you dry etched dentin?
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air dry, don't desiccate
short bursts of air not continuous |
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after etching dentin does it need to be rinsed?
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yes this removes excess acid gel to stop etch process
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why should the dentin be left slightly moistened?
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improves primer and adhesive ability to penetrate collagen fibrils to form hybrid layer, which is basis for micromechanical bond to dentin
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why must dentin remain moist?
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to keep collagen from collapsing (like sponge)
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collapsed dentin (like spaghetti noodles) is ______ permeable to hydrophilic monomers and creates weak interface
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less
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can poor drying technique of etched dentin produce pain?
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YES - seen in posterior teeth
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After etching and air dry of dentin, what is next and why?
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apply primer/resin - made of hydrophilic resins (monomers) in a water, alcohol, or acetone carrier -photoinitiators present (yellow color)
continuously applied for 15-20 sec |
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What do the resins placed after etching do for dentin bonding (wet bonding)?
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penetrate into the inherently moist dentin surface and copolymerize with the composite restoration;
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what is the hybrid layer, where does it come from
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some of the bonds form from resin tags extending into tubules; most of bond strength is form resin penetrating and adapting to demineralized intertubular dentin and exposed collagen fibres; reslultant interdiffusion zone often ermed the hybrid layer
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Why do you lightly blow air over the adhesive (resin/primer) in dentin bonding?
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thins out the adhesive layer which is inherently weak, drives off volatile carrier used to thin primer/adhesive mix
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does the primer need to be cured in dentin bonding?
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yes, 10-20 sec cure of adhesive, surface remains unpolymerized due to oxygen inhibition
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after the primer has been light cured in dentin bonding, what is next?
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apply composite resin into restoration
no more than 2 mm increments - light scatters and not enough gets into deeper areas to assure good polymerization |
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what are the 3 major elements or strategies of dentin bonding?
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smear layer - removed with acid etch similar to enamel etch (shorter time)
hydrophilic (love water) Monomers (primers) used instead of hydrophobic |