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61 Cards in this Set
- Front
- Back
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What is an alloy?
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2 or more mutually soluble metals
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What are a few dental alloys?
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Ag- silver
Sn -tin Cu - copper |
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What is an amalgam?
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an alloy containing mercury (hg)
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Explain mercury
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it is a metal that is a liquid at room temperature
combines with other metal particles into an alloy reacts and forms a set bond |
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What sort of restoration would you use amalgam on?
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Class 1 and Class 2
better for permanent than deciduous |
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What class might you put amalgam in if not good moisture control?
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Class 5
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What is best material to hold up against water?
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Amalgam and GIC is worst?
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What is the powder in an amalgam?
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silver, copper and tin
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What metal had a high content in the 80's in amalgam?
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Copper
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What does admixed or dispersed describe?
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the way in which copper was added
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What is the foundation for the amalgam when setting?
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Tin and Copper
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What is the "glue" made out of for the setting?
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silver/mercury
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if the formation of the tin/mercury is weak what will happen?
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amalgam won't be as strong and will be prone to corroding
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Can the tin/mercury phase still form if the material is not manipulated correctly?
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YES
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What did higher copper prevent from forming?
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additional phases
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What are a few advantages of amalgam?
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strong and hard
saves money lasts longer |
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If the marginal seal is reasonable and improves with time what is the result of tin/copper?
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tin and copper corrosion products migrate to the margins
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On a small scale corrosion products are good as they help seal but on a big scale what is the problem?
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free mercury left behind can react with residual alloy particles forming more matrix phase and weakening the restoration
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When you say amalgam advantage is that it lasts long, how long can they last usually?
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up to 30 years
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What will happen to restoration if there are sharp angles?
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stress concentration
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What will happen if your cavo surface angle is greater than 90*?
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will undermine enamel
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What will happen if cavo surface is less than 90*?
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will give mass bulk
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What are some disadvantages of amalgam?
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aesthetics
retention is mechanical bulk needed for strength high thermal conductivity |
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Do you need a insulating layer under the amalgam?
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YES, usually vitrebond
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Why do you need a liner in amalgam?
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because metal conducts hot and cold
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Do you line the whole prep are just the dentin?
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just dentin
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When the amalgam is mixed what should the final product look like?
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it should have a sheeny appearance and not appear too wet or grainy
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What is approximate working time with amalgam?
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1-2 minutes
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Why does the surface of the amalgam go shiny when plugging into cavity?
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the mercury rises to the top, which can be carved away when set
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Do you put amalgam in in small increments?
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YES 1mm depth at time
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Where should you start plugging the amalgam?
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in the middle and move towards the walls
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Should you overfill prep and if so by how much and why?
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YES, by 1mm so that when you carve the layer off it is just the mercury rich layer
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What instruments should you use to carve amalgam?
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Cleoid-discoid
Hollenback Shofu carver |
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When carving you should carve parallel to the margins of the prep using existing inclines, Why?
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edge of instrument rests on adjacent tooth structure
aids in reproducing tooth inclines and contours enables flash over the margins to be removed avoids over carving |
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What should you do in a class 2 before removing matrix band?
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define marginal ridge and occlusal embrasures with back of sickle probe
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What could happen if you carve too deep when finishing amalgam?
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the bulk will be reduced and the rest may fracture
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How can you smooth the surface after finished carving?
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with a cotton pellet or burnisher
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When you are smoothing off with a cotton pellet or burnisher what must you avoid?
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too much pressure and heat as this may bring mercury to the surface
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How long does amalgam take before patient can eat on that side?
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1-2 hours but 8 is best
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How long will it take for amalgam to be fully set and you can finish of if needed?
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24 hours
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What can you use to finish amalgam once set?
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stones or finishing burs
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Give a few examples of burs being used for finishing
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pear, round or flame
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What can you use to smooth but must be used on wet surface?
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rubbers or discs
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What is the common cause of breakdown in the margins?
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ditching of the margins as a result of fracture at edge of the amalgam
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What is likely to occur if the thin excess of material left over the margins?
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margin will take chunk with it
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Why would expansion occur and amalgam extrude from cavity?
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die to moisture inclusion, excess mercury corrosion
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How does mercury (Hg)exist?
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elemental- vapour colorless and odorless
inorganic- silver mercury organic - methyl |
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Which forms of mercury are more readily absorbed?
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mercury vapour and organic mercury
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Which form of mercury is less readily excreted?
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organic mercury
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Once mercury is absorbed into the circulatory system where can it be deposited?
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in any tissue e.g brain, liver, kidneys
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What can a chromic exposure to ligh levels of mercury result in?
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effects CNS
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When do signs and symptoms occur when exposed to too much mercury?
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around 300 micrograms
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What is the average intake from air food and water on a daily basis?
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10-20 micro grams
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what is the contribution of dental amalgams estimated at?
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3 micrograms
that is for 12+ occulsal rests |
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What is the main concern of mercury from a clinical point of view?
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the vapour
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When is the Hg likely to release when putting in rest?
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with dry polishing and removal of amalgams
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From an environmental perspective what is main concern of amalgam?
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when mercury is cremated and vapours go into environment
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What are measures to reduce exposure to mercury?
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standard PPE
working area well ventilated one use disposable capsules immediate clean up if spilled wash skin with sap and water after contact with Hg avoid heat production during cutting/polishing amalgam waste storage under old radiographic fixer in sealed container waste capture from plumbing systems |
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Why would you replace a perfectly sound amalgam?
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if pt was allergic to them
and proper use of safety precaustions |
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When would you avoid using amalgam?
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on pregnant women
in children in people with kidney disease |
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Does removal of amalgam lead to improved general health
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NO, as far as studies show
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