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39 Cards in this Set
- Front
- Back
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Amalgamation process
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1. mercury wets AgSn (gamma) phase
2. mercury reacts with outside particles 3. Matrix formed 4. Unreacted particles are captured 5.Mercury in entirely consumed |
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What are the 2 basic amalgam compositions
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1. low copper (2-5% copper)
These are older amalgams has lots of corrosion and looks black 2. High copper (12-30% copper) 1980s last longer |
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Describe how the copper content changes the reaction
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?
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What are the different types of geometry of particles
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1. lathe cut
2. spherical 3. blended |
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Describe the difference between good and bad zinc content
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The good last 25-50% longer, its an oxygen scavenger (2Zn + O2 -->2ZnO) and suppresses oxidation.
Its bad if its contaminated with moisture, zinc reacts with water to release H2 gas. There is also a delayed expansion of amalgam |
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What is permite C and its characteristics
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What we use and is
1. admixed (blend) 2. High copper 3. Zn containing |
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Describe some relevant points of the amalgam controversy?
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Mercury is toxic
amalgam has mercury lack scientific evidence |
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Name some things we use metals for
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1. Cast metal crowns
2. Metal-ceramic crowns 3. Implants to replace missing teeth 4.Poste & core to restore endo treated teeth |
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What are some characteristics of metalic bonds
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1. metalic elements have 1, 2, or 3 electrons in their outer shell, which are key to metalic bonds,electrons are loosely bound to nucleus. This makes metal more mobile
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Whats the process of molten metal to formation of grains
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Molten metal --->nuclei of crystalization--->crystal growth--->formation of grains
?P.3 |
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What is a metal alloy? and difference between a pure metal?
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Mixture of 2 or more metals. Pure metals can slide but but alloys can't slide past each other and are stronger. These are used for crowns and amalgams
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What are some noble metals that strengthen
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Au, Ag, Pd, Pt
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What are some characteristics of ceramic bonds
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1. Ionic and covalent bonding
2. Stronger than metalic bonds 3. Covalent >ionic 4. nonmobile ions Check? |
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What is the microstructure of ceramics
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Mixture of metalic and nonmetalic elements
- most common is SiO2, AlO3, K2O SiO4 |
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_________is the building block of ceramics
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SiO4
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1
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1
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1
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1
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1
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1
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What are some characteristics of polymer bonds
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1. covalent bonds
2. high molecular wt. 3 Long molecules composed of nonmetalic elements |
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How do polymers form? and difference between monomer,polymers
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Polymerization
Monomers are liquid Polymers are sold |
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Name some important words to associate with polymerization
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initiator molecule
activation free radicals monomer initiation propagation polymer termination |
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T/F polymerization is a slow reaction?
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False can be very fast
MMA to PMMA goes very fast 1000000 units/ sec |
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What can ceramics be adhered to?
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Enamel and dentin
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Name the four types of adhesioin? Hint DAME
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Diffusion
Adsorption Mechanical adhesion electrostatic adhesion |
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______is the most important type of adhesion in dentistry, has impermeable surface, uses the lock and key effect and enamel bonding is an example.
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Mechanical adhesion
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________is used in dentin bonding, uses interphase, one is mixed into another
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Diffusion
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________uses chemical bonding(covalent, ionic, hydrogen, van der waals) and glass ionomer adhesion is an example.
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adsorption and surface reaction
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_______is a type of adhesion between charged molecules and is less important and the weakest.
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Electrostatic adhesioin
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Describe what etching does and some properties
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?
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Etching
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?
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What makes it possible to bond to enamel. Whats the most important one
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Macrotags (interprism)
Microtags(intraprism)*most important |
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What happens as a restoration gets larger?
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Ratio of dentin surface to enamel surface gets larger and have to rely more on dentin bonding than enamel bonding
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What makes dentin different than enamel when it comes to bonding
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Dentin is porous and wet (hydrophilic)
Resins are hydrophobic.Dentin structure varies with and experience. |
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Initial preparation is likel to encounter ______ _____
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tubular dentin
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What do you when bonding to tubular dentin
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Smear layer created from prep (ground collagen and HA) adheres and interferes with bonding
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When bonding to tubular dentin what type of etch do you do?
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3o second etch with 37% H3PO4 and then rinse and remove excess water but DO NOT DESSICATE
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What does wet dentin have?
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inter-collagen fibers
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Hybrid layer
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?p.8
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What makes bonding tough with dentin
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oil and water don't mix
The glass surface is hydrophilic. Monomers are hydrophobic. Poor wetting and no bonding |
