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120 Cards in this Set
- Front
- Back
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State the general similarities between current resin composite restorative materials
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1. They are all currently based on dimethacrylate resins (for setting, and cross-linked --- shrinks on polymerization)
2. They all contain inorganic fillers 3. There is a coupling agent, to ensure bonding betwen resin and inorganic filler (silane compunds) 4.) There are appropriate chemicals that can generate free radical in the presence of visible light activation 5.) Minor constitiuents ( Pigmens, polymerizatoin stabilizers, UV absorbers) |
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What are the pros and cons of dimethacrylate resins
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Pros
- setting mechanism - cross linking for mechanical properties Cons- shrinks on polymerization |
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What is the coupling agent between composite resin and inorganic filler
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Silane compounds
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What are the reasons for the minor constituents found in resin composite restorative material
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Pigments = good esthetics
- Polymerization stabilizers = polymerization of material on storage - UV absorbers - prevent discoloration in sunlight. |
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What prevents premature polymerization in resin composites
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polymerization stabilizers
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WHat is the main polymer system used for resin composites
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Bowmen's resin
- it combines two methacrylate groups to --> dimethacylate. This results in 1. A place for free radical addtion polymerization to occur --> setting mechanism 2.) the dimethacrylate regions allow for a place for Rigid croos links to form between the polymer chains!!!!! |
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Alternative to Bowmen's Resin for use in composite resins
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Urethane dimethacrylate
From the name you could guess that it is similar to the previous component we talked about. |
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What are a few problems that can occur with Bowmen's resin.
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Bis GMA is very viscous and so something needs to be added to let it flow
- That something si TEGDMA - a monomer - Problem with the monomer --> causes increases in shrinkagea! |
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Why are fillers used in resin composites
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They cause an increase in some key properties.
- Alone, they are very RIGID and experience high stress when under strain. - WHen added with a resin (as long as the ceramic is more rigid and the polymer is well-bonded) you well get better properties. |
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What can fillers be made of
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Quartz (SiO2), barium glass, zirconia, silica
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What are the various size of fillers
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- macrofills >10 um
- midfills 1-10 um - minifills 0.1 - 1 um - microfills 0.04 - 0.1 um - nanofills (o.o2 - o.o7 um) - hybrid materials |
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How much filler COULD be found in a composite resin.
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Anywhere from 40 - 80% of the value.
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Properties of quartz as a filler
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- prepared by grinding process
- Rough surface - Very hard - not opaque to X-rays |
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Properties of Zirconia/silica
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- sol-gel production process
- approzimately spherical particles - Good polishability - Continuum in sizes - High packing density |
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Properties of inorganic fillers (microfillers)
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- 0.04 - 0.1
- Amorphous silica (SI02) - o.o4 - Lower filler content needed = 35% - Low mechanical properties - Excellent polishability |
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Properties of inorganic fillers nonofiller
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0.02 - 0.075 nanoparticals
- High filler loading - excellent mechanical properties ability to take and retain high polish |
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What are microhybrid fillers and hybird fillers
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They are essentially the same thing but the hybrid fillers uses bigger particals to get the jobe done 5 um.
glass particals + microfillers |
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What type of filler is associated with contiuum filled classifications
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Zicronica silica ---> one large contiuum of sizes seen
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what coupleing agent is used in resin composites to bring together the polymer (Resin) and the filler.
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Silane coupleing agent
The key is that it can react with both the polymer and has the ability to hydrolize the ceramic! |
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Classify compositions according to their viscosity and handling characteristics.
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They are usually classified according to the filler.
There are the types of fillers - macrofilled - microfilled - hybrid filled - continum filled - nanofilled Also ased on the flow properties - Flowable - packable |
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The following materials are listed in the range of composite materials, explain the filler that goes with each
- Sealant - Microfilled - Flowable - Hybrid & continum - Packable and condensable |
-Sealants = Based on dimethacyaltes
- Microfilled = amorphous silica (SiO2) - Flowable = syrinable - hybird & continuum - glass particla and zicronia silica - |
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What are the parameters for ability to be syringed
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material of low viscosity
- material that will show shear thinning (pseudoplasticity) - reversible structural beakdown (to make sure th materail doesn't slump |
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What property is it considered to have a material that has: A material which has lower viscosity at faster rates of shearing
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Pseudoplasticity -- shear thinning
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What is another name for reersible structural breakdown
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Thixotropy
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How does thixotrophy or reversible structural breakdown occur
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During syringing, hydrogen bonds are broken and then they quickly reform tomate sure the mnaterial doesn't slump.
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What is the goal of getting a packable composite?
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You essentially want to mimic the condensation properties of dental amalgam
- generally not as great as expected. |
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What is a compomer?
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Compomers” are recently introduced products marketed as a new class of dental materials. These materials are said to provide the combined benefits of composites (the “comp” in their name) and glass ionomers (“omer”). Based on an critical review of the literature, the author argues that “compomers” do not represent a new class of dental materials but are merely a marketing name given to a dental composite.
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According to dr. Combe what are they
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Poly-acid modified resins (composites) + glass ionomers
They set by polymerization only. |
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WHat happens when a glass isomer is added to a resin composte material
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Mechanical = reduces toughness
Adhesive = MAY add chemical contribution to bond strength Dimensional = have polymerization on shrinkage still Chemical - no essential aquaeous phase |
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Define Adsorptoin:
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RXN of a substance with a surface
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Define Adsorption:
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RXN of a substance which involves the bulk of the materla
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Chemisorption
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Chemical reaction (not usually reversible) taken place
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Physical adsorptoi:
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Where van der Waals forces operate, more readily reversible than chemisorption
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What factors contribute to bond strength ( one or more...)
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1. Chemical Bonding
2. Micromechanical adhesion --> liquid flows in and holds on 3. Hybridization bonding --> one layer meets up with a second making a hybrid layer. |
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When talking about the factors that contribute to bond strength... what are the key components of each of the following
1. Chemical adhesion 2. Micromechanical adhesion 3. Hybridization bonding |
1 = Glass-ionomer cements to tooth substance
2. Adhesion to etched enamel 3. Bonding to dentin |
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How does chemical adhesion take place
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By Chemisorption
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how does micromechanical adhesion take place
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Physical adsorption (surface) (+ micormechanical)
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How does Hybridization take place
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Absorption (diffused control) - this is through the bulk of the material.
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What is a big difference between the use of the adhesion mechanism between enamel and dentin.
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Enamel uses, chemical and micromechanical adhesion
Dentin: uses all three mechanism |
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What are the effects of acid etching on enamel
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- cleans
- selective de-calcification - porous surface - Reactive surface (high energy ONLY IF IT"S CLEAN AND DISINFECTED - unpolymerized resin can penetrate pores and then polymerize in situ (in place) |
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How much does surface energy changedin etched enamel vs. unetched enamel.
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Etched has almost twice as much surface energy.
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Define Desiccation
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Drying!
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List some practical factors to think of in enamel bonding
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- concentration of etchant
- pH of etchant - time etching - technique of etching - recognition of appearance of adequate etching - washing - DRYING |
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What happens to the bond strenght if micro-organisms are around.
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There is a decreasae in the critical surface tension and the shear bond strength
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What does the durability of enamel bonding depend on
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1. initial ethcing -- dry, lacking microbes?
2. fully integrated interface between polymer and etch enamel - mechanical properties of polymer - Mechanical properties of enamel. |
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Do self-etch systems work on uncut enamel
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They seem to work on cut enamel but on uncut enamel the ph has to be low enough to actually burn away the tooth structure whic is one of the only reasons that Adper Promopt works
It has an acidity close to that of phosphoric acid |
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What is a pit and fissure sealant?
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A material that is placed in pits and fissures of teeth in order to prevent or arrest the development of denal caries.
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Why do we use sealants?
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Best way to keep the area from cavities!
- makes easier to clean - fluoride protection - barier against food and microbes. |
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History of sealants?
old attempts now used |
Old = Super glue ( cyanoacylates)
- Now --> acid etching + dimethacrylate resin (Bis-GMA + TEGDMA) |
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What is our concerns with sealants
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If incomplete polmerizatoin occurs, TEGDMA may come out of the resin
--> TEGMA degraded via enzymes --> Bi |
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What is said to be a total etch ?
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Getting Dentin and Enamel bonded at the same time!
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What are used to make sealants?
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With the range of filled dimethacrylate ploymers?
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What material is used when bonding on orthodontic brackets and what are some concerns with this material?
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Matrial = resin based with acid etch
- Concerns = white spot lesion - concern = iatrogenic damage on de-bonding. |
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What are biocompatibility concerns when it comes to to bonding on enamel
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If there is incomplete polymerization --> TEGDMA would come out in resin
- The TEGDMA could degrade via enzymes and end up in vivo. |
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What is total Etch
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Simultaneous etching and condition of enamel or dentin of a prepared tooth cavity
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What alters the surface of dentin?
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- scatches in cavity prep
- Partially denatured smear layer - if it is denatured far enough, you will have smear plugs which goes all the way into tubules. |
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What does acid etch do on dentin
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Remove the smear layer
- demineralize the most superficial hydroxyapatitie crystals |
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What does dentin look like after conditioning?
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The dental tubules are exposed.
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What are the consequences of conditioning dentin
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1. infiltration of monomers into dentin
2. The formation of a hybrid layer made of resin, collagen, and hydroxyapatite. 3. Tensil strength 4. Absorption (bulk of the goods) |
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What are the components of hybridization bonding
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- Resin
- Hybrid layer - dentin. |
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What types of bonds occur with dentin hybridizations.
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- Chemical = covalent (chemisorption
- micormechanical = physical adsorption - Hybridization = Adsorptoin (diffusion controlled) USES ALL SYSTEMS! |
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What are the general steps used for etching
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Conditioner, primer, adhesive
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Classifiy Etch Rinse vs, self etch rince
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There are four types
3 E&R - Everything done individually. conditioner- wash - primer - adhesive 2 E&R Combine last two steps - Conditioner - wash - primer/adhesive _________________________ no wash needed 2 SEA: Conditioner/ primer - adhesive 1 SEA Conditioner/Primer/Adhesive I think the number stands for the amount of actual steps that are taken discluding the wash. They get more consise with time. |
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Nature of Dimethacrylate monomers
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An example is Bowman's resin
- they will react with monomers of restoration to form covalent bonds |
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Nature of hydrophilic monomer and common name
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2 - HEMA
Readily polymerizes hydrophilic |
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Nature of polyalkenoic acids or methacrylates with carboxylate groups
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trying to mimic chemical adhesive effects of zinc
- cement |
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nature of inorganic fillers
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mechanical toughening, analagous to resin composites
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Nature of solvating agents
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water
ethanol ethanol/water acetone (too volatile |
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Nature of initiators
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Like those for the resin composites.
should be cured before application to ensure the liquid is set. |
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Define the causes of microleakage
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Margins allow stuff in
- known of for years. |
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Define the causes of nanoleakage
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passage of leakants of small size through the material
In adhesives that were HEMA rich, droplets were also abserved due to water absorption from dentin caused by osmoss. |
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in vivo durability of bonding
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The "gold stars of care are still older than the etch and rinces which are fairly new"
The gold star is the 3 step, ethanol water based etch and rinse adhexive. |
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WHat are the problems with the all in one adhesives
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- to hydrophilic
- high solven concentration phase separations may occur - acidic components may adversely affect initiator system. |
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Define Amalgam
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An ally of mercury with another metal
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What is amalgamation
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A reaction of mercury with other metalic materials,
can occur at room temp. |
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What are the practical stages in the preparation of an amalgam restoration
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1. Mix powdered allowy with liquid mercury
2. Metallic paste is formed 3. Paste is packed (condensed) into tooth cavity 4.) Material is carved to correct anatomy 5.) Amalgamation RXN occurs 6. Material sets and hardens 7.) Restoration is polished |
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Describe the intermetallic compond Ag3Sn (y phase)
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The component of Ag3Sn
- 73.15 % Ag - 26.85 % Sn How does it come together - Melting Ag and Sn in the correct proportions - solifiy the material - Ue a machine to form a powder (lathe cut) OR - can be preparted into spherical form by the use of atomizing material |
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Discuss the reaction of Ag3Sn with Hg
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silver tin (Ag3Sn) + mercury yields three compounds
1. Silver- mercury (y1) 2. Tin - mercury (y2) Also some unreacted Ag3Sn (found in the core) rest is the combo of y1 and y2 |
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Describe the structure of the set material resulting in the reaction of Ag3Sn (y phase) with mercury
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A core of unreacted powder surrouned by reaction products from the reaction
- JUST LIKE CEMENT - the tin-mercury actually collects in small particles - the Sliver mercury seems to dispurse well. |
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What is the composition of traditional amalgams
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There was mixture of Silver, tin copper and zin, listed from highest to lowest
- CU increases the strength and hardness Zn is the Scavenger for Ox during manufacture --> this helps the production of the product |
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In the traditional, low Cu alloys, what happens when the amount of Sn, Ag is off
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To much Sn ( tin) --> contraction on setting
TOo much Ag (silver) --> excess expansion on setting |
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Why was the level of Cu low in the first alloys
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It was believed that that more than 6% Cu would result in excess expansion
However it is actually better with more. |
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What are some limitations of the low copper amalgams
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The y2 phase is the biggest problem ( Tin- mercury)
- This is because it is the softest of the three phases - Most likely liable to suffer from electolytic corrosions |
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Within amalgam, what is the anode and what is the catode?
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y1 (with silver) is the CATHOD
y2 is the ANODE (tin is just easier to influence than silver. ) |
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What is the consequences of corrosoin of y2 (tin)
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Sn 7-8Hg
- Tin salts get together with Mercury resulting in: - more amalgamation - mercuroscopic expansion (compromises marginal integrity) |
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How was the corroson of y2 fixed
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The amount of Cu was increased- Make the compound essentially free of the y2 compound
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Discuss the effects of Cu in "high copper" amalgam
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There is no y2
This is because it forms initially but hten reacts to form a: - coppper tin compound - more y1 |
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classify contemporary "high copper" amalgams
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two main types
- Blended allowy (dispersally - Single composition (tytin) |
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Tell me a little about blended high- Cu alloys.
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Made of two parts.
Ag3 Sn ( like older allowys) PLUS 1 part of weight silver copper (copper in the traditional is only about 4% and is up to 12% in the dispersalloy - Creates AgCu spheers - REALLY A VARIETY OF SIZED ANd SHAPES |
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What is the composition of single composition of high Cu alloys
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Sybraloy has 28% copper while Tytin has 13 % copper.
The difference betwee the two is mainly made by altering amount of silver |
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What is the the difference in condensation characteristic between high cooper amalgam blended and single composition
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Blended --> positive packing --> this occurs during condensation
- Single Composition -- less condensation force--> harder to pack --> causes possible open proximal contact - Tytin claims to be easier to condense (advantge of the contrast. |
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Discuss the structure of contemporary 'high copper' amalgam
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when it is set it will have these areas that are just composed fo Cu and Sn so they essentially act as silver sink holes to not allow corrosion.
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Discuss the manipulative factors that influence the properties of amalgam.
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Think about each variation that could happen in each of the prep steps.
Things we must considers - ratio of ratio/mercury - mixing (trituratino) - condensation - carving - polishing - mercury hygiene |
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How can the alloy/hg ratio be altered
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now this is not much of a factor to deal with because th Alloy and Hg are encapsulated
- about 50-50 mixture - Too much Hg can result in a altered restoration |
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Ho do you ensure you get the mixing time correct if using a machine or hand
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make sure your machine has accurate time teler.
If undermixed - unworkable mix If overtriturated - excess contraction will occur during setting. |
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What term refers to the hand mixing of amalgam
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Trituration
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How do you manipulate the Aim phase of the condensation condensation stage
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- place material in increments
- express excess mercury - ensure that the incruments are bonded to each ofther and avoid layers. |
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What are all considerations of Condensation>
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1. goals: get amalgam where it has to go and ensure that you have good bonding!
2. time of condensation 3. Force and spped of condensation |
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Why do you carve amalgam
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To remove excess hg-rich layer of material.
- to establish the correct anatomy |
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why do you want to polish amalgam?
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- less plaque deposition
- less chance fo corrosion - mimics surface of enamel with is smooth. |
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What is the pneumonic that covers all of the properties of a biomaterial/?
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1. B = Biocompatibility
2. I = interfacial properties 3. C = Chemical - corrosion - electrochemical 4. M = mechanical = other physical properties 5. E = Esthethic 6. P= practicability. |
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What are some key consideratinos in discussing the properties of amalgam biocompatibility?
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There has been much debate to if it is safe of not but it comes down to understandy the properties of amalgam (form, quantity, frequency, and effect)
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What does the toxicity of mercury depend on?
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- The form
- Quantity of exposure - Frequency of exposure - efect that each from of mercury has. |
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What forms can mercury be found in?
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1. Liquid
2. vapor 3. Intermetallic compound 4. Organometallic compound |
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What should be understood about liquid mercury
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If it is swallowed, it is not absorbed well. It also has a high vapor pressure (what you really have to watch out for)
The big problems are: - kin contact to absorb HG - few people have alergic responses. |
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What should be understood about vapor mercury
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- It is very toxic and dangerous to dental staff
- It can cross alveolar membrane and get into the blood stream |
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What should be remembered about mercury found in the form of intermetallic compounds?
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They are found normally in set amalgam.
They are COMPARATIVELY insoluble and harmless |
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What should be remembered about mercury found in the form of organomercury compounds
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- Methy Mercury is VERY TOXIC
- this is wht you can find in certain fish. - Can be found in amalgam but it's comparatively low to other things. |
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What keeps an amalgam restoration in place?
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1. Mechanical retention ( undercuts)
2. Bonding systems work on dentin, but not really amalgam. |
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What is happening with amalgam at the material tooth interface.
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There is a lot of stress because the Amalgam is able to expand and contract more than the tooth and is more thermally conducting than the tooth.
Amalgam has more exteme properties. |
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what does the modulus of elasticity essentially stand for
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The stiffness of a material.
Higher modulus --> high stiffness |
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what is the interface
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The area between the mateial and the tooth substance
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What is marginal microleakage
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the passage of bacteria, fluids, molecules, or ions between a cavity wall and restorative material
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What leads to an increase or decrease in amalgam corrosoin
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Increase
- low copper = y2 corrosion - gold in contact with amalgam Decreases - increased amount of copper - polishing |
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With time what happens to the strength of amalgam
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It increses!
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What is creep
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The slow deformation of material understress
- seen in amalgam - less seen in high Cu amalgam |
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What does "ditching" or margins mean
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Marginal failure, usually do to the creep of the material so...
see less in higher Cu (newer) amalgam. |
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What must be considered about the termal conduction of amalgam
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- Amalgam is a good thermal conductor! It conducts heat so placement must be made with the pulp chambers location in mind.
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WHat could happen if zinc and mosture is avalibe during amalgam setting.
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It would cause the amalgam to flow and expand.
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Why id dental amalgam seldomly used alond when restoring a tooth?
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becuase there would be problems with:
- microleakage - adhesion -termal conductivity |
