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57 Cards in this Set
- Front
- Back
What percentage of restorations utilize amalgams?
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75%
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Amalgam has served as a restorative material in dentistry for how many years?
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Over 165 years
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T/F Hypersensitivity to amalgam is common
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False rare
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Amalgam _______ at a similar rate as tooth structure
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wears
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Amalgam is the least ______ of the long term materials
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expensive
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What is the composition of amalgam?
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Silver (Ag) 40‐60%; Tin 27‐30%; Copper (Cu) 6‐30%; Zinc (Zn) 0.01‐2%; Palladium (Pd) less than 1%; Indium (In) 10‐15% in the Hg (Steve Thompson Can’t Zee Past Insults)
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An admix of amalgam is a mixture of what?
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Mixture of lathe cut and spherical particles. (Irregular was first used – lathe cut type)
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When an alloy containing 27% tin is slowly cooled below a temperature of ___, an intermediate compound Ag3Sn known as the _____ phase is produced ***
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480° and gamma
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Mercury diffuses into the γ phase and reacts with the silver and tin portions of the particles forming two compounds?
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1. Silver‐mercury (γ1 phase: Ag2Hg3)
2. Tin‐mercury (γ2 phase: Sn7‐8Hg) |
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During the reaction Mercury dissolves into the amalgam. What amount dissolves into Copper, Silver, and Tin?
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1 mg Hg in copper, 10 mg of Hg in Silver, 170 mg of Hg in Tin
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What phase causes the γ2 phase to be eliminated?
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ε phase
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Which phase is the weakest and most susceptible to corrosion?
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γ2 phase
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What is the compressive strength of amalgam?
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Good: (200 MPa in 1 hour)
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Is the tensile strength of amalgam good?
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No; (50 MPa)
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The elastic modulus is considered?
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Good ( 11‐62 MPa)
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What is creep as it relates to amalgams?
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Permanent deformation under static loads (0.05 – 6.3%)
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Dimensional changes are greatest during the first _____.
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20 minutes (contraction)
after that expansion then stable at 6‐8 hours, capable of normal function after 24‐48 hours. |
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When zinc containing alloy gets contaminated with water it will cause?
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Excessive expansion
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Corrosion: Progressive ___________of a metal by chemical or electrochemical reaction.
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Destruction (Porosity > marginal integrity < Loss of strength and release of metallic products)
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Phosphate buffer solutions _________ the corrosion process (saliva).
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inhibit
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Zinc cause too much ________. Therefore, new products have aimed to remove zinc.
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expansion
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Admixed allows for _______ time compared to spherical.
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more
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True or False: Even 2‐3 sec difference can produce an over or under mixed amalgam.
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True
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A dull and crumbly amalgam would indicate what type of error?
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Undermixed
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A soupy and tends to stick to walls of the capsule would indicate?
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Overmixed
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What instrument is used to place the amalgam restoration?
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Amalgam carrier
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Ivoclar‐Vivadent used in the dental clinic eliminates which phase?
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γ2 phase
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Lateral condensation is important for __________ particles of amalgam
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spherical
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Use a flat‐faced small __________ to condense the amalgam over the pulpal and gingival floor of the preparation.
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condenser
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Each increment of amalgam should fill ____ to ____ the cavity prep.
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1/2 to 1/3
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Overpack prep by ______ .
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1mm
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Condensation of the mix should be completed in ______ to ______ minutes.
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2.5 to 3.5
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True or False: Deep occlusal grooves should be carved into the restoration?
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False
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An amalgam restoration overcarved more than _____ should be replaced.(referred to as ditching)
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0.2 mm
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To smooth the carved surface you may use a _____ _________ _________.
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Dry cotton pellet
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Try to avoid occlusal contacts on the _________.
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Inclines
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Finishing and Polishing of the restoration will make it less prone to ___________ and ‐___________.
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Tarnishing and corrosion
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What is the recommended sequence for performing an amalgam restoration?
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1. Field Isolation
2. Establish outline 3. Remove Caries 4. Smooth cavosurface angle 5. Place base if deep or close to pulp. 6. Insert amalgam as explained. |
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_________ __________ wears at a rate similar to tooth structure?
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Dental Amalgam
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What type of Amalgam do we use at CWRU?
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Valiant PhD by Ivoclar Vivadent
High Copper Alloy (to eliminate the gamma2 phase) 1. Higher Strength 2. Less Corrosion 3. Better longevity at the margins |
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What does Undermixed amalgam look like?
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Dull and crumbly
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What does properly mixed amalgam look like?
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Shiny and separates in a single mass
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What does overmixed amalgam look like?
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Soupy and tends to stick to the walls of the capsule
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What is creep, when referring to amalgams?
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Permanent deformation under static loads (0.05-6.3%). Creep is especially prevalent in high mercury amalgams
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What is the compressive strength like in amalgams?
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Good (200 MPa in 1 hour)
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What is the tensile strength of amalgam like?
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Bad (43-58 MPa)
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What is the elastic modulus like in amalgams?
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Good (11-62 MPa)
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Why do you tell patients not to eat anything for 1 hour after having an amalgam placed?
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The amalgam reaction is not complete
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What happens when a Zinc containing alloy gets contaminated with water?
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Excessive expansion
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What is the dimensional change of amalgam during the first 20 minutes?
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Contraction
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What is the dimensional change of amalgam after 20 minutes then stabilizes at 6-8 hours
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Expansion
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What is the Υ phase?
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When an alloy containing Tin is cooled below 480 deg C an intermetallic compound is formed (Ag3Sn)
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What happens when the Υ phase is mixed with mercury?
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Υ1 phase (Ag2Hg3) Silver-mercury
Υ2 phase (Sn7-8Hg) Tin-mercury |
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What is the amalgamation reaction?
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See Above
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What causes the Υ2 phase to be eliminated within a few hours after its formation?
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ε phase
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What phase is the weakest and most susceptible to corrosion?
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gamma 2 phase
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How do amalgam particles present?
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Irregular or Lathe-cut
Spherical Admixed |